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Ian Field

"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.