On Saturday, July 8, 2017 at 9:58:10 PM UTC-4, wrote:
On Saturday, July 8, 2017 at 7:15:05 PM UTC-4, Dimitrij Klingbeil wrote:
On 07.07.2017 19:36, rickman wrote:
wrote on 7/7/2017 1:01 PM:
On Friday, July 7, 2017 at 12:09:33 PM UTC-4, rickman wrote:

The charge pump circuit was bothering me as the diode seemed to be
backwards. Then I realized it isn't making 24 volts from 12 volts, it's
pumping up the 24 volts to something higher! What is the voltage on
pin 3
of the LA7833? The cap is only rated for 35 volts, so it isn't
making 48
volts. But clearly pin 3 should have something on it higher than 24
volts.
What does the pump drive signal on pin 7 look like?

--

Rick C

pin 3 of 7833 is 25.65 v. pins 2 and 15 are opposite polarity. pump
drive signal is a .5 volts upside down sawtooth.

i appreciate the time taken here. i could just send this out, but i
think i am close, just not there.

If pin 7 pump drive signal is only half a volt, I would say your problem
is there. Pin 3 should clearly be more than 25 volts and it is this
signal that drives that voltage. Is pin 3 at all steady or is it also a
waveform? You should measure the voltage with the scope, not the meter.

On Saturday, July 8, 2017 at 9:58:10 PM UTC-4, wrote:
On Saturday, July 8, 2017 at 7:15:05 PM UTC-4, Dimitrij Klingbeil wrote:
On 07.07.2017 19:36, rickman wrote:
wrote on 7/7/2017 1:01 PM:
On Friday, July 7, 2017 at 12:09:33 PM UTC-4, rickman wrote:

The charge pump circuit was bothering me as the diode seemed to be
backwards. Then I realized it isn't making 24 volts from 12 volts, it's
pumping up the 24 volts to something higher! What is the voltage on
pin 3
of the LA7833? The cap is only rated for 35 volts, so it isn't
making 48
volts. But clearly pin 3 should have something on it higher than 24
volts.
What does the pump drive signal on pin 7 look like?

--

Rick C

pin 3 of 7833 is 25.65 v. pins 2 and 15 are opposite polarity. pump
drive signal is a .5 volts upside down sawtooth.

i appreciate the time taken here. i could just send this out, but i
think i am close, just not there.

If pin 7 pump drive signal is only half a volt, I would say your problem
is there. Pin 3 should clearly be more than 25 volts and it is this
signal that drives that voltage. Is pin 3 at all steady or is it also a
waveform? You should measure the voltage with the scope, not the meter.

wrote in message
...
On Thursday, July 6, 2017 at 3:58:22 PM UTC-4, John-Del wrote:
On Thursday, July 6, 2017 at 11:18:38 AM UTC-4, wrote:
On Thursday, July 6, 2017 at 7:17:12 AM UTC-4, rickman wrote:
wrote on 7/6/2017 1:00 AM:
On Wednesday, July 5, 2017 at 9:34:41 AM UTC-4,
wrote:
On Wednesday, July 5, 2017 at 3:39:44 AM UTC-4, John Robertson
wrote:
On 2017/07/05 12:35 AM, wrote:
And if it has a large value (1000-4700uF) cap inside the
feedback loop that is failing, that can cause severe linearity
issues.

G²


Granted, however the OP did say he recapped the monitor and I
didn't
want to doubt his statement.

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

its an IC, an LA7833( nte1773) . i'll change it out and see what
happens. i did change out every cap, and it was exactly the same.
no better, no worse.

thanks much

just got done replacing the vertical IC, la7833. no change in the
image. no better, no worse.

Looks like the 24 volt supply is generated by doubling the 12 volt
supply.
Measure the 24 volt supply at pin 6. I bet something is wrong that
this is
only 12 volts, maybe the diode?

--

Rick C


https://na.suzohapp.com/pdf/service_...vp2_manual.pdf

https://na.suzohapp.com/pdf/service_..._schematic.pdf

B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out
good, and look like brand new. no physical damage.

Not saying the yoke is the problem, but a single turn shorted to an
adjacent turn will not change the resistance reading on your dmm, but a
single shorted turn will totally collapse the magnetic field of the coil.

A ringer is the best instrument to check for shorted turns.

not sure what a ringer is, but im pretty sure i dont have one. you mean
like a tone generator, and you move it around the yoke ?

The DSE one has a comparator rigged to generate spike pulses - the ringing
pulses clock a logic 1 along a shift register and basically counts how many
times the inductor rings.

The schematic is floating about the web, and there's nothing hard to find in
the parts list.

On 7/9/2017 1:13 PM, Ian Field wrote:
The DSE one has a comparator rigged to generate spike pulses -
the ringing pulses clock a logic 1 along a shift register and
basically counts how many times the inductor rings.

The schematic is floating about the web, and there's nothing
hard to find in the parts list.

https://www.flippers.com/fbt-main.html



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

---
This email has been checked for viruses by AVG.
http://www.avg.com

On Sunday, July 9, 2017 at 2:43:31 PM UTC-4, Foxs Mercantile wrote:
On 7/9/2017 1:13 PM, Ian Field wrote:
The DSE one has a comparator rigged to generate spike pulses -
the ringing pulses clock a logic 1 along a shift register and
basically counts how many times the inductor rings.

The schematic is floating about the web, and there's nothing
hard to find in the parts list.

https://www.flippers.com/fbt-main.html



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

---
This email has been checked for viruses by AVG.
http://www.avg.com
i swapped the D360 diode with another from the board, no difference. i dont really understand from the schematic what the pump up circuit is. it has 24V thru a electrolytic cap in series to pin7 . is that an input or an output? the same circuit( before the cap) goes to pin 3. there is only about 1/2 volt on pin 7. is it supposed to pulse, pin 7 pulling down the 24 v?

On 2017/07/08 7:38 PM, John-Del wrote:
On Saturday, July 8, 2017 at 9:58:10 PM UTC-4, wrote:
On Saturday, July 8, 2017 at 7:15:05 PM UTC-4, Dimitrij Klingbeil wrote:
On 07.07.2017 19:36, rickman wrote:
wrote on 7/7/2017 1:01 PM:
On Friday, July 7, 2017 at 12:09:33 PM UTC-4, rickman wrote:

The charge pump circuit was bothering me as the diode seemed to be
backwards. Then I realized it isn't making 24 volts from 12 volts, it's
pumping up the 24 volts to something higher! What is the voltage on
pin 3
of the LA7833? The cap is only rated for 35 volts, so it isn't
making 48
volts. But clearly pin 3 should have something on it higher than 24
volts.
What does the pump drive signal on pin 7 look like?

--

Rick C

pin 3 of 7833 is 25.65 v. pins 2 and 15 are opposite polarity. pump
drive signal is a .5 volts upside down sawtooth.

i appreciate the time taken here. i could just send this out, but i
think i am close, just not there.

If pin 7 pump drive signal is only half a volt, I would say your problem
is there. Pin 3 should clearly be more than 25 volts and it is this
signal that drives that voltage. Is pin 3 at all steady or is it also a
waveform? You should measure the voltage with the scope, not the meter.
They don't use a smoothing cap so I guess the voltage will pulse with
the drive. During retrace you don't need a high voltage on pin 3.
Retrace is when the voltage goes below 24 volts and the diode is forward
biased to charge up the cap again.

I think you said you already replaced the LA7833, so there are only two
other parts. When you say pin 7 is "upside down", do you mean it is
normally high and drops low or it is going negative? I would expect it
to be near 24 volts during the picture time and drops low during retrace
as the cap charges. I guess the question is how does the waveform on
pin 3 look? I would expect it mostly near 48 volts dropping slightly
below 24 volts during retrace. Pin 7 should definitely have a
significant pulse voltage on it.

Did you check D360 (the "bootstrap" diode from 24V in the pump circuit)?

It may be shorted and pulling the "pumped" supply "down" to 24V. The IC
will most likely need the pumped supply for one half of the screen only..

i did pull up one leg of D360 and checked it, it checked good. pin 7 never goes anywhere near 24 volt. there is a .5 volts poorly defined waveform, almost looks like ripple. im thinking it should be a 24v sawtooth? i am thinking something on the board may be pulling down pin 7?

thanks

You can't check this diode with a dmm... I posted above:


"I didn't read back through all the posts, but if you haven't, check the pump up diode. The anode will be connected to the Vcc and the cathode to the pump up pin of the vert IC. A weak diode here will cause all sorts of havoc (don't check it with a dmm - they often sag under load)."


That is a most interesting point, the 1N4937 diode is indeed a fast
switching diode and it certainly appears to be critical for building the
vertical deflection. Your point about sagging under load could indeed be
correct for this problem as described by the OP.

Learn something every day, thanks!

John :-#)#

wrote in message
...
On Sunday, July 9, 2017 at 2:43:31 PM UTC-4, Foxs Mercantile wrote:
On 7/9/2017 1:13 PM, Ian Field wrote:
The DSE one has a comparator rigged to generate spike pulses -
the ringing pulses clock a logic 1 along a shift register and
basically counts how many times the inductor rings.

The schematic is floating about the web, and there's nothing
hard to find in the parts list.

https://www.flippers.com/fbt-main.html



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

---
This email has been checked for viruses by AVG.
http://www.avg.com
i swapped the D360 diode with another from the board, no difference. i
dont really understand from the schematic what the pump up circuit is. it
has 24V thru a electrolytic cap in series to pin7 . is that an input or an
output? the same circuit( before the cap) goes to pin 3. there is only
about 1/2 volt on pin 7. is it supposed to pulse, pin 7 pulling down the
24 v?

There's sometimes an electro with ambiguous purpose (also on audio amps). It
bootstraps the output to the bias network for the output transistor bases.
Its almost positive feedback that reduces drive current requirement for the
output pair and improves linearity.

On Monday, July 10, 2017 at 3:17:06 PM UTC-4, Ian Field wrote:
wrote in message
...
On Sunday, July 9, 2017 at 2:43:31 PM UTC-4, Foxs Mercantile wrote:
On 7/9/2017 1:13 PM, Ian Field wrote:
The DSE one has a comparator rigged to generate spike pulses -
the ringing pulses clock a logic 1 along a shift register and
basically counts how many times the inductor rings.

The schematic is floating about the web, and there's nothing
hard to find in the parts list.

https://www.flippers.com/fbt-main.html



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

---
This email has been checked for viruses by AVG.
http://www.avg.com
i swapped the D360 diode with another from the board, no difference. i
dont really understand from the schematic what the pump up circuit is. it
has 24V thru a electrolytic cap in series to pin7 . is that an input or an
output? the same circuit( before the cap) goes to pin 3. there is only
about 1/2 volt on pin 7. is it supposed to pulse, pin 7 pulling down the
24 v?

There's sometimes an electro with ambiguous purpose (also on audio amps). It
bootstraps the output to the bias network for the output transistor bases.
Its almost positive feedback that reduces drive current requirement for the
output pair and improves linearity.

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks

On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated..

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather than shutting down, the half scan is how it was made to shutdown. still, doesnt shutdown usually not shut down the vertical scan ? i dont think anything on this unit is the usual. the manual for it is near useless, very little info. another thing, the schematic shows two pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this board, and the same board on ebay has both pairs jumped. its a hair puller. pin 13 on the 7851 is the x ray protection pin, and it needs to be a specific voltage or the chip shuts down. the manual says that, but doesnt say the voltage. im going to end up buying a chasssi, but i'd still like to know what the heck is wrong with mine.

thanks

On Monday, July 10, 2017 at 10:25:35 PM UTC-4, wrote:
On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather than shutting down, the half scan is how it was made to shutdown. still, doesnt shutdown usually not shut down the vertical scan ? i dont think anything on this unit is the usual. the manual for it is near useless, very little info. another thing, the schematic shows two pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this board, and the same board on ebay has both pairs jumped. its a hair puller. pin 13 on the 7851 is the x ray protection pin, and it needs to be a specific voltage or the chip shuts down. the manual says that, but doesnt say the voltage. im going to end up buying a chasssi, but i'd still like to know what the heck is wrong with mine.

thanks

When projection TVs started hitting the market, manufacturers soon learned that a scan loss in either direction would immediately destroy the CRTs. In response, manufacturers learned to not start the HV until both deflections were established, and shut down same if one was lost or even diminished by a fixed percent. The point is that a vertical collapse would not be the result of a shutdown, but a cause.

Read my previous post again. One of the last CRT TVs I worked on was a Zenith 35" console with a stubborn vert (slow to fill, weird linearity issues).. It turned out that the board became conductive from leaked electrolyte and dust. Heating and cooling the board affected the deflection, but no components were themselves temperature sensitive. I ended up pulling the flyback, smps transformer, and any inductor that looked like it could hold water and immersed the whole board in a parts cleaner. Once assembled, the vertical was perfect and didn't drift.

On Tuesday, July 11, 2017 at 7:14:23 AM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 10:25:35 PM UTC-4, wrote:
On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather than shutting down, the half scan is how it was made to shutdown. still, doesnt shutdown usually not shut down the vertical scan ? i dont think anything on this unit is the usual. the manual for it is near useless, very little info. another thing, the schematic shows two pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this board, and the same board on ebay has both pairs jumped. its a hair puller. pin 13 on the 7851 is the x ray protection pin, and it needs to be a specific voltage or the chip shuts down. the manual says that, but doesnt say the voltage. im going to end up buying a chasssi, but i'd still like to know what the heck is wrong with mine.

thanks

When projection TVs started hitting the market, manufacturers soon learned that a scan loss in either direction would immediately destroy the CRTs. In response, manufacturers learned to not start the HV until both deflections were established, and shut down same if one was lost or even diminished by a fixed percent. The point is that a vertical collapse would not be the result of a shutdown, but a cause.

Read my previous post again. One of the last CRT TVs I worked on was a Zenith 35" console with a stubborn vert (slow to fill, weird linearity issues). It turned out that the board became conductive from leaked electrolyte and dust. Heating and cooling the board affected the deflection, but no components were themselves temperature sensitive. I ended up pulling the flyback, smps transformer, and any inductor that looked like it could hold water and immersed the whole board in a parts cleaner. Once assembled, the vertical was perfect and didn't drift.

this board is so clean you could eat off of it. im also looking into that it may be lacking the pulse feed from the flyback to the vert ic.

wrote on 7/10/2017 10:25 PM:
On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather than shutting down, the half scan is how it was made to shutdown. still, doesnt shutdown usually not shut down the vertical scan ? i dont think anything on this unit is the usual. the manual for it is near useless, very little info. another thing, the schematic shows two pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this board, and the same board on ebay has both pairs jumped. its a hair puller. pin 13 on the 7851 is the x ray protection pin, and it needs to be a specific voltage or the chip shuts down. the manual says that, but doesnt say the voltage. im going to end up buying a chasssi, but i'd still like to know what the heck is wrong with mine.

If the high voltage section shuts down you would lose the brightness of the
electron beam, no? Sounds from your description the electron beam is
clearly visible when the deflection collapses.

--

Rick C

On Tuesday, July 11, 2017 at 11:38:23 AM UTC-4, rickman wrote:
wrote on 7/10/2017 10:25 PM:
On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather than shutting down, the half scan is how it was made to shutdown. still, doesnt shutdown usually not shut down the vertical scan ? i dont think anything on this unit is the usual. the manual for it is near useless, very little info. another thing, the schematic shows two pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this board, and the same board on ebay has both pairs jumped. its a hair puller. pin 13 on the 7851 is the x ray protection pin, and it needs to be a specific voltage or the chip shuts down. the manual says that, but doesnt say the voltage. im going to end up buying a chasssi, but i'd still like to know what the heck is wrong with mine.

If the high voltage section shuts down you would lose the brightness of the
electron beam, no? Sounds from your description the electron beam is
clearly visible when the deflection collapses.

--

Rick C

i put a probe on pin 4 of LA7851, the vertical deflector ic chip. its a pulse from the AFC terminal on the flyback. there is virtually no pulse, just a half volt . from the flyback afc terminal, i get a 90 volt shape that looks like a half rectified sine wave, just the top of the sine wave. 90 volt seems low. i think there has to be a pulse at pin 4 for the IC to operate. i bought a working chassis on ebay, and will check some pins outputs, i dont want to give up now.

wrote in message
...
On Tuesday, July 11, 2017 at 11:38:23 AM UTC-4, rickman wrote:
wrote on 7/10/2017 10:25 PM:
On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no
better. regarding d360 possibly sagging, i did swap it with another
on the board, and it was the same. i'll have to keep digging, but any
help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on
low and watch the picture as you do. I'd bet dollars to donuts at
this point that the picture stretches out. You said you recapped the
monitor but was this all the larger electros that are known to cause
issues (like a kit) or *everything*. There are often low value
electrolytics back at the signal generator side used for signal
coupling that get juicy on the bottom and cause issue either from low
esr (they can be juicy and still check OK) or from conductive
contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try
washing the board with a suitable cleaner and acid brush, removing the
"jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather
than shutting down, the half scan is how it was made to shutdown.
still, doesnt shutdown usually not shut down the vertical scan ? i
dont think anything on this unit is the usual. the manual for it is
near useless, very little info. another thing, the schematic shows two
pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this
board, and the same board on ebay has both pairs jumped. its a hair
puller. pin 13 on the 7851 is the x ray protection pin, and it needs to
be a specific voltage or the chip shuts down. the manual says that,
but doesnt say the voltage. im going to end up buying a chasssi, but
i'd still like to know what the heck is wrong with mine.

If the high voltage section shuts down you would lose the brightness of
the
electron beam, no? Sounds from your description the electron beam is
clearly visible when the deflection collapses.

--

Rick C

i put a probe on pin 4 of LA7851, the vertical deflector ic chip. its a
pulse from the AFC terminal on the flyback. there is virtually no pulse,
just a half volt . from the flyback afc terminal, i get a 90 volt shape
that looks like a half rectified sine wave, just the top of the sine wave.
90 volt seems low. i think there has to be a pulse at pin 4 for the IC to
operate. i bought a working chassis on ebay, and will check some pins
outputs, i dont want to give up now.

The number sounds familiar - but its been a while.

some vertical chips were just the power stage while others included the ramp
generator etc. If it does and you've tried replacement, you might need to
consider what was said about shorted turns on the yoke.

Some of the passives can cause trouble, but they're easier to test than
shorted turns.

"John Robertson" wrote in message
...
On 2017/07/08 7:38 PM, John-Del wrote:
On Saturday, July 8, 2017 at 9:58:10 PM UTC-4, wrote:
On Saturday, July 8, 2017 at 7:15:05 PM UTC-4, Dimitrij Klingbeil wrote:
On 07.07.2017 19:36, rickman wrote:
wrote on 7/7/2017 1:01 PM:
On Friday, July 7, 2017 at 12:09:33 PM UTC-4, rickman wrote:

The charge pump circuit was bothering me as the diode seemed to be
backwards. Then I realized it isn't making 24 volts from 12 volts,
it's
pumping up the 24 volts to something higher! What is the voltage on
pin 3
of the LA7833? The cap is only rated for 35 volts, so it isn't
making 48
volts. But clearly pin 3 should have something on it higher than 24
volts.
What does the pump drive signal on pin 7 look like?

--

Rick C

pin 3 of 7833 is 25.65 v. pins 2 and 15 are opposite polarity.
pump
drive signal is a .5 volts upside down sawtooth.

i appreciate the time taken here. i could just send this out, but i
think i am close, just not there.

If pin 7 pump drive signal is only half a volt, I would say your
problem
is there. Pin 3 should clearly be more than 25 volts and it is this
signal that drives that voltage. Is pin 3 at all steady or is it also
a
waveform? You should measure the voltage with the scope, not the
meter.
They don't use a smoothing cap so I guess the voltage will pulse with
the drive. During retrace you don't need a high voltage on pin 3.
Retrace is when the voltage goes below 24 volts and the diode is
forward
biased to charge up the cap again.

I think you said you already replaced the LA7833, so there are only
two
other parts. When you say pin 7 is "upside down", do you mean it is
normally high and drops low or it is going negative? I would expect
it
to be near 24 volts during the picture time and drops low during
retrace
as the cap charges. I guess the question is how does the waveform on
pin 3 look? I would expect it mostly near 48 volts dropping slightly
below 24 volts during retrace. Pin 7 should definitely have a
significant pulse voltage on it.

Did you check D360 (the "bootstrap" diode from 24V in the pump
circuit)?

It may be shorted and pulling the "pumped" supply "down" to 24V. The IC
will most likely need the pumped supply for one half of the screen
only..

i did pull up one leg of D360 and checked it, it checked good. pin 7
never goes anywhere near 24 volt. there is a .5 volts poorly defined
waveform, almost looks like ripple. im thinking it should be a 24v
sawtooth? i am thinking something on the board may be pulling down pin
7?

thanks

You can't check this diode with a dmm... I posted above:


"I didn't read back through all the posts, but if you haven't, check the
pump up diode. The anode will be connected to the Vcc and the cathode to
the pump up pin of the vert IC. A weak diode here will cause all sorts
of havoc (don't check it with a dmm - they often sag under load)."


That is a most interesting point, the 1N4937 diode is indeed a fast
switching diode and it certainly appears to be critical for building the
vertical deflection. Your point about sagging under load could indeed be
correct for this problem as described by the OP.

Its a fairly common type number - I've certainly encountered *MUCH* less
reliable diodes along the way.

Not that I've never had to replace one, but they're not prominent in the
stock faults list.

On 2017/07/12 8:29 AM, wrote:
On Tuesday, July 11, 2017 at 11:38:23 AM UTC-4, rickman wrote:
wrote on 7/10/2017 10:25 PM:
On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather than shutting down, the half scan is how it was made to shutdown. still, doesnt shutdown usually not shut down the vertical scan ? i dont think anything on this unit is the usual. the manual for it is near useless, very little info. another thing, the schematic shows two pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this board, and the same board on ebay has both pairs jumped. its a hair puller. pin 13 on the 7851 is the x ray protection pin, and it needs to be a specific voltage or the chip shuts down. the manual says that, but doesnt say the voltage. im going to end up buying a chasssi, but i'd still like to know what the heck is wrong with mine.

If the high voltage section shuts down you would lose the brightness of the
electron beam, no? Sounds from your description the electron beam is
clearly visible when the deflection collapses.

--

Rick C

i put a probe on pin 4 of LA7851, the vertical deflector ic chip. its a pulse from the AFC terminal on the flyback. there is virtually no pulse, just a half volt . from the flyback afc terminal, i get a 90 volt shape that looks like a half rectified sine wave, just the top of the sine wave. 90 volt seems low. i think there has to be a pulse at pin 4 for the IC to operate. i bought a working chassis on ebay, and will check some pins outputs, i dont want to give up now.


It that is a working chassis for that board it would be great if you can
photograph the 'scope images and post them somewhere. I can capture them
and add to flippers library of tech tips for folks to use in the future...

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On 2017/07/12 11:24 AM, Ian Field wrote:


"John Robertson" wrote in message
...
On 2017/07/08 7:38 PM, John-Del wrote:
On Saturday, July 8, 2017 at 9:58:10 PM UTC-4, wrote:
On Saturday, July 8, 2017 at 7:15:05 PM UTC-4, Dimitrij Klingbeil
wrote:
On 07.07.2017 19:36, rickman wrote:
wrote on 7/7/2017 1:01 PM:
On Friday, July 7, 2017 at 12:09:33 PM UTC-4, rickman wrote:

The charge pump circuit was bothering me as the diode seemed to be
backwards. Then I realized it isn't making 24 volts from 12
volts, it's
pumping up the 24 volts to something higher! What is the
voltage on
pin 3
of the LA7833? The cap is only rated for 35 volts, so it isn't
making 48
volts. But clearly pin 3 should have something on it higher
than 24
volts.
What does the pump drive signal on pin 7 look like?

--

Rick C

pin 3 of 7833 is 25.65 v. pins 2 and 15 are opposite polarity.
pump
drive signal is a .5 volts upside down sawtooth.

i appreciate the time taken here. i could just send this out, but i
think i am close, just not there.

If pin 7 pump drive signal is only half a volt, I would say your
problem
is there. Pin 3 should clearly be more than 25 volts and it is this
signal that drives that voltage. Is pin 3 at all steady or is it
also a
waveform? You should measure the voltage with the scope, not the
meter.
They don't use a smoothing cap so I guess the voltage will pulse with
the drive. During retrace you don't need a high voltage on pin 3.
Retrace is when the voltage goes below 24 volts and the diode is
forward
biased to charge up the cap again.

I think you said you already replaced the LA7833, so there are
only two
other parts. When you say pin 7 is "upside down", do you mean it is
normally high and drops low or it is going negative? I would
expect it
to be near 24 volts during the picture time and drops low during
retrace
as the cap charges. I guess the question is how does the waveform on
pin 3 look? I would expect it mostly near 48 volts dropping slightly
below 24 volts during retrace. Pin 7 should definitely have a
significant pulse voltage on it.

Did you check D360 (the "bootstrap" diode from 24V in the pump
circuit)?

It may be shorted and pulling the "pumped" supply "down" to 24V.
The IC
will most likely need the pumped supply for one half of the screen
only..

i did pull up one leg of D360 and checked it, it checked good. pin
7 never goes anywhere near 24 volt. there is a .5 volts poorly
defined waveform, almost looks like ripple. im thinking it should be
a 24v sawtooth? i am thinking something on the board may be pulling
down pin 7?

thanks

You can't check this diode with a dmm... I posted above:


"I didn't read back through all the posts, but if you haven't, check
the pump up diode. The anode will be connected to the Vcc and the
cathode to the pump up pin of the vert IC. A weak diode here will
cause all sorts of havoc (don't check it with a dmm - they often sag
under load)."


That is a most interesting point, the 1N4937 diode is indeed a fast
switching diode and it certainly appears to be critical for building
the vertical deflection. Your point about sagging under load could
indeed be correct for this problem as described by the OP.

Its a fairly common type number - I've certainly encountered *MUCH* less
reliable diodes along the way.

Not that I've never had to replace one, but they're not prominent in the
stock faults list.

Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.

Now pinball power supplies? Those we replace diodes from time to time...

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the 1n4001
to 1n4007, each with a higher voltage rating. My only thought is they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

"John Robertson" wrote in message
...
On 2017/07/12 11:24 AM, Ian Field wrote:


"John Robertson" wrote in message
...
On 2017/07/08 7:38 PM, John-Del wrote:
On Saturday, July 8, 2017 at 9:58:10 PM UTC-4, wrote:
On Saturday, July 8, 2017 at 7:15:05 PM UTC-4, Dimitrij Klingbeil
wrote:
On 07.07.2017 19:36, rickman wrote:
wrote on 7/7/2017 1:01 PM:
On Friday, July 7, 2017 at 12:09:33 PM UTC-4, rickman wrote:

The charge pump circuit was bothering me as the diode seemed to be
backwards. Then I realized it isn't making 24 volts from 12
volts, it's
pumping up the 24 volts to something higher! What is the voltage
on
pin 3
of the LA7833? The cap is only rated for 35 volts, so it isn't
making 48
volts. But clearly pin 3 should have something on it higher than
24
volts.
What does the pump drive signal on pin 7 look like?

--

Rick C

pin 3 of 7833 is 25.65 v. pins 2 and 15 are opposite polarity.
pump
drive signal is a .5 volts upside down sawtooth.

i appreciate the time taken here. i could just send this out, but i
think i am close, just not there.

If pin 7 pump drive signal is only half a volt, I would say your
problem
is there. Pin 3 should clearly be more than 25 volts and it is this
signal that drives that voltage. Is pin 3 at all steady or is it
also a
waveform? You should measure the voltage with the scope, not the
meter.
They don't use a smoothing cap so I guess the voltage will pulse
with
the drive. During retrace you don't need a high voltage on pin 3.
Retrace is when the voltage goes below 24 volts and the diode is
forward
biased to charge up the cap again.

I think you said you already replaced the LA7833, so there are only
two
other parts. When you say pin 7 is "upside down", do you mean it is
normally high and drops low or it is going negative? I would expect
it
to be near 24 volts during the picture time and drops low during
retrace
as the cap charges. I guess the question is how does the waveform
on
pin 3 look? I would expect it mostly near 48 volts dropping slightly
below 24 volts during retrace. Pin 7 should definitely have a
significant pulse voltage on it.

Did you check D360 (the "bootstrap" diode from 24V in the pump
circuit)?

It may be shorted and pulling the "pumped" supply "down" to 24V. The
IC
will most likely need the pumped supply for one half of the screen
only..

i did pull up one leg of D360 and checked it, it checked good. pin 7
never goes anywhere near 24 volt. there is a .5 volts poorly defined
waveform, almost looks like ripple. im thinking it should be a 24v
sawtooth? i am thinking something on the board may be pulling down pin
7?

thanks

You can't check this diode with a dmm... I posted above:


"I didn't read back through all the posts, but if you haven't, check
the pump up diode. The anode will be connected to the Vcc and the
cathode to the pump up pin of the vert IC. A weak diode here will
cause all sorts of havoc (don't check it with a dmm - they often sag
under load)."


That is a most interesting point, the 1N4937 diode is indeed a fast
switching diode and it certainly appears to be critical for building the
vertical deflection. Your point about sagging under load could indeed be
correct for this problem as described by the OP.

Its a fairly common type number - I've certainly encountered *MUCH* less
reliable diodes along the way.

Not that I've never had to replace one, but they're not prominent in the
stock faults list.

Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese? -
the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.

There was a European BA prefix family of diodes that I can't remember the
numerical bit that were seriously dodgy.

There was a block package E/W diode that could be single or double and had
an SK prefix (IIRC) that I routinely replaced whether they'd failed or not.

Not many in monitors - nearly all in TVs.

"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the 1n4001
to 1n4007, each with a higher voltage rating. My only thought is they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

Last time I ordered diodes - all the PIV grades were the same price, I just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

On Thursday, July 13, 2017 at 4:03:55 PM UTC-4, Ian Field wrote:
"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the 1n4001
to 1n4007, each with a higher voltage rating. My only thought is they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

Last time I ordered diodes - all the PIV grades were the same price, I just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

well, i got the new chassis and its working correctly. turns out my chassis i recapped and went all sorts of nuts on is most likely good. it was the control board with size, horz, vertical, contrast and the other adjustments. it plugs in via a ribbon cable. if i use my old control board with the new chassis, i get the same half image. i never thought control board, as i got the half image with the board connected and unconnected, and mvoing the pots made no difference. i have both boards and will go over the pots, resistors, 1 diode and 1 cap. see whats bad on the affected board, maybe the cable itself. its soldered, not crimped. i cant really test my old chassis, i had to use my old neck board, it was for a 13, not 19 inch monitor. not going to swap neck boards back and forth, im just glad its working. i will let all know if i find the control board issue

On 2017/07/14 4:03 PM, wrote:
On Thursday, July 13, 2017 at 4:03:55 PM UTC-4, Ian Field wrote:
"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the 1n4001
to 1n4007, each with a higher voltage rating. My only thought is they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

Last time I ordered diodes - all the PIV grades were the same price, I just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

well, i got the new chassis and its working correctly. turns out my chassis i recapped and went all sorts of nuts on is most likely good. it was the control board with size, horz, vertical, contrast and the other adjustments. it plugs in via a ribbon cable. if i use my old control board with the new chassis, i get the same half image. i never thought control board, as i got the half image with the board connected and unconnected, and mvoing the pots made no difference. i have both boards and will go over the pots, resistors, 1 diode and 1 cap. see whats bad on the affected board, maybe the cable itself. its soldered, not crimped. i cant really test my old chassis, i had to use my old neck board, it was for a 13, not 19 inch monitor. not going to swap neck boards back and forth, im just glad its working. i will let all know if i find the control board issue


Thanks for the update! I had forgotten about the sub-board controller
too, and we have run into that with other monitors.

I suspect now that one of the vertical potentiometers is damaged.....

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On Friday, July 14, 2017 at 7:19:32 PM UTC-4, John Robertson wrote:
On 2017/07/14 4:03 PM, wrote:
On Thursday, July 13, 2017 at 4:03:55 PM UTC-4, Ian Field wrote:
"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the 1n4001
to 1n4007, each with a higher voltage rating. My only thought is they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

Last time I ordered diodes - all the PIV grades were the same price, I just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

well, i got the new chassis and its working correctly. turns out my chassis i recapped and went all sorts of nuts on is most likely good. it was the control board with size, horz, vertical, contrast and the other adjustments. it plugs in via a ribbon cable. if i use my old control board with the new chassis, i get the same half image. i never thought control board, as i got the half image with the board connected and unconnected, and mvoing the pots made no difference. i have both boards and will go over the pots, resistors, 1 diode and 1 cap. see whats bad on the affected board, maybe the cable itself. its soldered, not crimped. i cant really test my old chassis, i had to use my old neck board, it was for a 13, not 19 inch monitor.. not going to swap neck boards back and forth, im just glad its working. i will let all know if i find the control board issue


Thanks for the update! I had forgotten about the sub-board controller
too, and we have run into that with other monitors.

I suspect now that one of the vertical potentiometers is damaged.....

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

the vert pot is open. schematic shows a 500ohm B pot. what is the b for. two of the pots have the b suffix. google had conflicting info that its a log pot, but testing the good one with a dvm, it looks linear( i need a battery for my analog meter) . thanks

On 2017/07/15 9:25 AM, wrote:
On Friday, July 14, 2017 at 7:19:32 PM UTC-4, John Robertson wrote:
On 2017/07/14 4:03 PM, wrote:
On Thursday, July 13, 2017 at 4:03:55 PM UTC-4, Ian Field wrote:
"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the 1n4001
to 1n4007, each with a higher voltage rating. My only thought is they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

Last time I ordered diodes - all the PIV grades were the same price, I just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

well, i got the new chassis and its working correctly. turns out my chassis i recapped and went all sorts of nuts on is most likely good. it was the control board with size, horz, vertical, contrast and the other adjustments. it plugs in via a ribbon cable. if i use my old control board with the new chassis, i get the same half image. i never thought control board, as i got the half image with the board connected and unconnected, and mvoing the pots made no difference. i have both boards and will go over the pots, resistors, 1 diode and 1 cap. see whats bad on the affected board, maybe the cable itself. its soldered, not crimped. i cant really test my old chassis, i had to use my old neck board, it was for a 13, not 19 inch monitor.. not going to swap neck boards back and forth, im just glad its working. i will let all know if i find the control board issue


Thanks for the update! I had forgotten about the sub-board controller
too, and we have run into that with other monitors.

I suspect now that one of the vertical potentiometers is damaged.....

John :-#)#

the vert pot is open. schematic shows a 500ohm B pot. what is the b for. two of the pots have the b suffix. google had conflicting info that its a log pot, but testing the good one with a dvm, it looks linear( i need a battery for my analog meter) . thanks


Cute, will try to remember damaged pots for the future. Always look for
the simple stuff first - usually my rule, but hey, who expects broken pots?

And, of course, I should.

John :-#(#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

"John Robertson" wrote in message
...
On 2017/07/15 9:25 AM, wrote:
On Friday, July 14, 2017 at 7:19:32 PM UTC-4, John Robertson wrote:
On 2017/07/14 4:03 PM, wrote:
On Thursday, July 13, 2017 at 4:03:55 PM UTC-4, Ian Field wrote:
"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail
at
random. They appeared to be the world's cheapest diode - early
Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall
the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the
1n4001
to 1n4007, each with a higher voltage rating. My only thought is
they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I
do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

Last time I ordered diodes - all the PIV grades were the same price, I
just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

well, i got the new chassis and its working correctly. turns out my
chassis i recapped and went all sorts of nuts on is most likely good.
it was the control board with size, horz, vertical, contrast and the
other adjustments. it plugs in via a ribbon cable. if i use my old
control board with the new chassis, i get the same half image. i never
thought control board, as i got the half image with the board
connected and unconnected, and mvoing the pots made no difference. i
have both boards and will go over the pots, resistors, 1 diode and 1
cap. see whats bad on the affected board, maybe the cable itself. its
soldered, not crimped. i cant really test my old chassis, i had to use
my old neck board, it was for a 13, not 19 inch monitor.. not going to
swap neck boards back and forth, im just glad its working. i will let
all know if i find the control board issue


Thanks for the update! I had forgotten about the sub-board controller
too, and we have run into that with other monitors.

I suspect now that one of the vertical potentiometers is damaged.....

John :-#)#

the vert pot is open. schematic shows a 500ohm B pot. what is the b for.
two of the pots have the b suffix. google had conflicting info that its
a log pot, but testing the good one with a dvm, it looks linear( i need a
battery for my analog meter) . thanks


Cute, will try to remember damaged pots for the future. Always look for
the simple stuff first - usually my rule, but hey, who expects broken
pots?

Pots became extinct just before CRTs. Now all the settings are on EEPROM.

On Sat, 15 Jul 2017 10:22:36 -0700, John Robertson
wrote:

On 2017/07/15 9:25 AM, wrote:
On Friday, July 14, 2017 at 7:19:32 PM UTC-4, John Robertson wrote:
On 2017/07/14 4:03 PM, wrote:
On Thursday, July 13, 2017 at 4:03:55 PM UTC-4, Ian Field wrote:
"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail at
random. They appeared to be the world's cheapest diode - early Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the 1n4001
to 1n4007, each with a higher voltage rating. My only thought is they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price. I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of them.

Last time I ordered diodes - all the PIV grades were the same price, I just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

well, i got the new chassis and its working correctly. turns out my chassis i recapped and went all sorts of nuts on is most likely good. it was the control board with size, horz, vertical, contrast and the other adjustments. it plugs in via a ribbon cable. if i use my old control board with the new chassis, i get the same half image. i never thought control board, as i got the half image with the board connected and unconnected, and mvoing the pots made no difference. i have both boards and will go over the pots, resistors, 1 diode and 1 cap. see whats bad on the affected board, maybe the cable itself. its soldered, not crimped. i cant really test my old chassis, i had to use my old neck board, it was for a 13, not 19 inch monitor.. not going to swap neck boards back and forth, im just glad its working. i will let all know if i find the control board issue


Thanks for the update! I had forgotten about the sub-board controller
too, and we have run into that with other monitors.

I suspect now that one of the vertical potentiometers is damaged.....

John :-#)#

the vert pot is open. schematic shows a 500ohm B pot. what is the b for. two of the pots have the b suffix. google had conflicting info that its a log pot, but testing the good one with a dvm, it looks linear( i need a battery for my analog meter) . thanks


Cute, will try to remember damaged pots for the future. Always look for
the simple stuff first - usually my rule, but hey, who expects broken pots?

And, of course, I should.

John :-#(#

Another vertical pot problem I have seen is leakage between the
potentiometer and a grounded case.

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"Chuck" wrote in message
...
On Sat, 15 Jul 2017 10:22:36 -0700, John Robertson
wrote:

On 2017/07/15 9:25 AM, wrote:
On Friday, July 14, 2017 at 7:19:32 PM UTC-4, John Robertson wrote:
On 2017/07/14 4:03 PM, wrote:
On Thursday, July 13, 2017 at 4:03:55 PM UTC-4, Ian Field wrote:
"Ralph Mowery" wrote in message
k.net...
In article ,
says...



Oddly enough I've had to replace every 1N4002 diode used in one
home
pinball game from the 1970s (Fischer's Sky Hawk) because they fail
at
random. They appeared to be the world's cheapest diode - early
Chinese?
- the body isn't a smooth cylinder rather it is lumpy.

I have to agree that diodes in monitors rarely fail, I can't recall
the
last time we traced a problem to a faulty diode.


I never did understand why they make a series of diodes like the
1n4001
to 1n4007, each with a higher voltage rating. My only thought is
they
make a batch like the microprocessors and test each one to see its
maximum rating and mark the lesser ones at a slightly lower price.
I do
think the 1n4007 may be a slightly different kind of makeup than the
others. Another thing is odd voltage cpacitors like a 63 volt unit.
Why not just 60 or 70 or even 65 due to the large tollorance of
them.

Last time I ordered diodes - all the PIV grades were the same price,
I just
ordered the highest grade in a larger quantity.

I have absolutely no idea how they grade production and marketing.

well, i got the new chassis and its working correctly. turns out my
chassis i recapped and went all sorts of nuts on is most likely good.
it was the control board with size, horz, vertical, contrast and the
other adjustments. it plugs in via a ribbon cable. if i use my old
control board with the new chassis, i get the same half image. i never
thought control board, as i got the half image with the board
connected and unconnected, and mvoing the pots made no difference. i
have both boards and will go over the pots, resistors, 1 diode and 1
cap. see whats bad on the affected board, maybe the cable itself. its
soldered, not crimped. i cant really test my old chassis, i had to
use my old neck board, it was for a 13, not 19 inch monitor.. not
going to swap neck boards back and forth, im just glad its working. i
will let all know if i find the control board issue


Thanks for the update! I had forgotten about the sub-board controller
too, and we have run into that with other monitors.

I suspect now that one of the vertical potentiometers is damaged.....

John :-#)#

the vert pot is open. schematic shows a 500ohm B pot. what is the b for.
two of the pots have the b suffix. google had conflicting info that its
a log pot, but testing the good one with a dvm, it looks linear( i need
a battery for my analog meter) . thanks


Cute, will try to remember damaged pots for the future. Always look for
the simple stuff first - usually my rule, but hey, who expects broken
pots?

And, of course, I should.

John :-#(#

Another vertical pot problem I have seen is leakage between the
potentiometer and a grounded case.

The one I've seen most of is loose rotor and flaky contact between wiper and
track.