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-   -   How change color TV to adjustable HVPS? (https://www.diybanter.com/electronic-schematics/347734-how-change-color-tv-adjustable-hvps.html)

Robert Baer[_3_] October 15th 12 10:25 AM

How change color TV to adjustable HVPS?
 
3 Attachment(s)
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Ian Field October 15th 12 09:16 PM

How change color TV to adjustable HVPS?
 


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can generate
24kV at?

Years ago I was messing around with the transformer from the PSU out of an
Amiga or somesuch - I'd turned the transformer around and driving one of the
original secondaries with a low VCEsat power transistor to get high voltage
from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc between
the pins of the high voltage winding. It was neccessary to complete the
circuitry including the regulation loop for safe operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.


Ian Field October 15th 12 10:38 PM

How change color TV to adjustable HVPS?
 


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out of
an Amiga or somesuch - I'd turned the transformer around and driving one
of the original secondaries with a low VCEsat power transistor to get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.

I have no idea as to how much current these nominally supply to the CRT;
suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would be
nice to have nearly the same current capability as far down as 20KV and
then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do run
another oscillator - why re-invent the wheel when it is there and nicely
round?


So,how could one vary the output voltage?


Pretty much the same as the original self oscillating chopper, control
transistor (2N2222 etc) clamps the chopper base on overvoltage. The control
circuit can be simple as you like or complex as you need - simple voltage
divider is probably best if you sample from the end of the ladder.


Robert Baer[_3_] October 15th 12 11:17 PM

How change color TV to adjustable HVPS?
 
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out of
an Amiga or somesuch - I'd turned the transformer around and driving one
of the original secondaries with a low VCEsat power transistor to get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.

I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would
be nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?


Jim Mueller October 16th 12 07:07 AM

How change color TV to adjustable HVPS?
 
On Mon, 15 Oct 2012 13:17:23 -0800, Robert Baer wrote:

Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out of
an Amiga or somesuch - I'd turned the transformer around and driving
one of the original secondaries with a low VCEsat power transistor to
get high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.

I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would
be nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?


One thing to note is that the picture tube is part of the circuit. The
coatings on the inside and outside of the tube form the filter capacitor
for the high voltage. If you intend to remove this part of the PC board
from the TV and use it as a stand-alone power supply, you will have to
provide a replacement capacitor; probably around 500 pF @ 40 KV should do
it.

--
Jim Mueller

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.

hifi-tek October 16th 12 05:49 PM

How change color TV to adjustable HVPS?
 

"Jim Mueller" wrote in message
eb.com...
On Mon, 15 Oct 2012 13:17:23 -0800, Robert Baer wrote:

Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out of
an Amiga or somesuch - I'd turned the transformer around and driving
one of the original secondaries with a low VCEsat power transistor to
get high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.

I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would
be nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?


One thing to note is that the picture tube is part of the circuit. The
coatings on the inside and outside of the tube form the filter capacitor
for the high voltage. If you intend to remove this part of the PC board
from the TV and use it as a stand-alone power supply, you will have to
provide a replacement capacitor; probably around 500 pF @ 40 KV should do
it.

Good point. TV flyback HV supplies are designed for a certain operating
point, if adjustment of the voltage is needed, the current capability will
suffer. I'd like to see schemo's of Glassman HV supplies to see how they do
it. They are wonderful supplies, and even more wonderfully expensive!
Tom



Robert Baer[_3_] October 16th 12 07:04 PM

How change color TV to adjustable HVPS?
 
Ian Field wrote:


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out of
an Amiga or somesuch - I'd turned the transformer around and driving one
of the original secondaries with a low VCEsat power transistor to get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.

I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would be
nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do run
another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?


Pretty much the same as the original self oscillating chopper, control
transistor (2N2222 etc) clamps the chopper base on overvoltage. The
control circuit can be simple as you like or complex as you need -
simple voltage divider is probably best if you sample from the end of
the ladder.

Thank you for not reading the question and avoiding what i asked for.


Robert Baer[_3_] October 16th 12 07:11 PM

How change color TV to adjustable HVPS?
 
hifi-tek wrote:
"Jim wrote in message
eb.com...
On Mon, 15 Oct 2012 13:17:23 -0800, Robert Baer wrote:

Ian Field wrote:


"Robert wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out of
an Amiga or somesuch - I'd turned the transformer around and driving
one of the original secondaries with a low VCEsat power transistor to
get high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would
be nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?


One thing to note is that the picture tube is part of the circuit. The
coatings on the inside and outside of the tube form the filter capacitor
for the high voltage. If you intend to remove this part of the PC board
from the TV and use it as a stand-alone power supply, you will have to
provide a replacement capacitor; probably around 500 pF @ 40 KV should do
it.

Good point. TV flyback HV supplies are designed for a certain operating
point, if adjustment of the voltage is needed, the current capability will
suffer. I'd like to see schemo's of Glassman HV supplies to see how they do
it. They are wonderful supplies, and even more wonderfully expensive!
Tom


Seems all adjustable HV supplies are in the $100 and up (mostly up)
range; cannot afford that.
The TV was wonderfully inexpensive (about $2.75 with sales tax).

Anybody know the current capability and/or what the CRT anode draws
at nominal brightness (30KV)?


Ian Field October 16th 12 09:49 PM

How change color TV to adjustable HVPS?
 


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out of
an Amiga or somesuch - I'd turned the transformer around and driving
one
of the original secondaries with a low VCEsat power transistor to get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit - the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would be
nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do run
another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?


Pretty much the same as the original self oscillating chopper, control
transistor (2N2222 etc) clamps the chopper base on overvoltage. The
control circuit can be simple as you like or complex as you need -
simple voltage divider is probably best if you sample from the end of
the ladder.

Thank you for not reading the question and avoiding what i asked for.



I chose to interpret the question as not being silly - the TV sweep section
is not designed for PWM (you might get away with burst mode thogh).

It seemed more sensible to assume you were asking how to regulate the
voltage on the PSU which was designed for PWM in the first place.


Ian Field October 16th 12 09:51 PM

How change color TV to adjustable HVPS?
 


"Robert Baer" wrote in message
...
hifi-tek wrote:
"Jim wrote in message
eb.com...
On Mon, 15 Oct 2012 13:17:23 -0800, Robert Baer wrote:

Ian Field wrote:


"Robert wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out
of
an Amiga or somesuch - I'd turned the transformer around and driving
one of the original secondaries with a low VCEsat power transistor to
get high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit -
the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would
be nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?

One thing to note is that the picture tube is part of the circuit. The
coatings on the inside and outside of the tube form the filter capacitor
for the high voltage. If you intend to remove this part of the PC board
from the TV and use it as a stand-alone power supply, you will have to
provide a replacement capacitor; probably around 500 pF @ 40 KV should
do
it.

Good point. TV flyback HV supplies are designed for a certain operating
point, if adjustment of the voltage is needed, the current capability
will
suffer. I'd like to see schemo's of Glassman HV supplies to see how they
do
it. They are wonderful supplies, and even more wonderfully expensive!
Tom


Seems all adjustable HV supplies are in the $100 and up (mostly up)
range; cannot afford that.
The TV was wonderfully inexpensive (about $2.75 with sales tax).

Anybody know the current capability and/or what the CRT anode draws at
nominal brightness (30KV)?


Pick a CRT type No & download the datasheet.


hifi-tek October 16th 12 09:51 PM

How change color TV to adjustable HVPS?
 

"Robert Baer" wrote in message
...
hifi-tek wrote:
"Jim wrote in message
eb.com...
On Mon, 15 Oct 2012 13:17:23 -0800, Robert Baer wrote:

Ian Field wrote:


"Robert wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out
of
an Amiga or somesuch - I'd turned the transformer around and driving
one of the original secondaries with a low VCEsat power transistor to
get high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit -
the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would
be nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?

One thing to note is that the picture tube is part of the circuit. The
coatings on the inside and outside of the tube form the filter capacitor
for the high voltage. If you intend to remove this part of the PC board
from the TV and use it as a stand-alone power supply, you will have to
provide a replacement capacitor; probably around 500 pF @ 40 KV should
do
it.

Good point. TV flyback HV supplies are designed for a certain operating
point, if adjustment of the voltage is needed, the current capability
will
suffer. I'd like to see schemo's of Glassman HV supplies to see how they
do
it. They are wonderful supplies, and even more wonderfully expensive!
Tom


Seems all adjustable HV supplies are in the $100 and up (mostly up)
range; cannot afford that.
The TV was wonderfully inexpensive (about $2.75 with sales tax).

Anybody know the current capability and/or what the CRT anode draws at
nominal brightness (30KV)?

I think I read somewhere in Sony's literature that a 32" trinitron crt can
pull about 90 watts of HV power, so it would be about 3 ma.



Ian Field October 17th 12 11:52 PM

How change color TV to adjustable HVPS?
 


"Ian Field" wrote in message
...


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out
of
an Amiga or somesuch - I'd turned the transformer around and driving
one
of the original secondaries with a low VCEsat power transistor to get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit -
the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would be
nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do run
another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?

Pretty much the same as the original self oscillating chopper, control
transistor (2N2222 etc) clamps the chopper base on overvoltage. The
control circuit can be simple as you like or complex as you need -
simple voltage divider is probably best if you sample from the end of
the ladder.

Thank you for not reading the question and avoiding what i asked for.



I chose to interpret the question as not being silly - the TV sweep
section is not designed for PWM (you might get away with burst mode
thogh).

It seemed more sensible to assume you were asking how to regulate the
voltage on the PSU which was designed for PWM in the first place.



Another thing I just remembered - a TV flyback unit is highly resonant, that
means you'd have to keep the scan yoke in circuit (and accomodate the
physical assembly on the bench) to keep the resonant system tuned. Without
resonance you don't get the full flyback EHT voltage.


Robert Baer[_3_] October 19th 12 09:29 AM

How change color TV to adjustable HVPS?
 
hifi-tek wrote:
"Robert wrote in message
...
hifi-tek wrote:
"Jim wrote in message
eb.com...
On Mon, 15 Oct 2012 13:17:23 -0800, Robert Baer wrote:

Ian Field wrote:


"Robert wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU out
of
an Amiga or somesuch - I'd turned the transformer around and driving
one of the original secondaries with a low VCEsat power transistor to
get high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit -
the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would
be nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?

One thing to note is that the picture tube is part of the circuit. The
coatings on the inside and outside of the tube form the filter capacitor
for the high voltage. If you intend to remove this part of the PC board
from the TV and use it as a stand-alone power supply, you will have to
provide a replacement capacitor; probably around 500 pF @ 40 KV should
do
it.

Good point. TV flyback HV supplies are designed for a certain operating
point, if adjustment of the voltage is needed, the current capability
will
suffer. I'd like to see schemo's of Glassman HV supplies to see how they
do
it. They are wonderful supplies, and even more wonderfully expensive!
Tom


Seems all adjustable HV supplies are in the $100 and up (mostly up)
range; cannot afford that.
The TV was wonderfully inexpensive (about $2.75 with sales tax).

Anybody know the current capability and/or what the CRT anode draws at
nominal brightness (30KV)?

I think I read somewhere in Sony's literature that a 32" trinitron crt can
pull about 90 watts of HV power, so it would be about 3 ma.


At least that gives me a range or order of magnitude; this TV is a 9"
Hitachi, set power spec is 49W and i measured 35W at the supply line to
the flyback xfmr.
So..crude refining would imply current to be about 1.2mA.
Thanks.


Robert Baer[_3_] October 19th 12 09:33 AM

How change color TV to adjustable HVPS?
 
Ian Field wrote:


"Ian Field" wrote in message
...


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU
out of
an Amiga or somesuch - I'd turned the transformer around and
driving one
of the original secondaries with a low VCEsat power transistor to get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit
- the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it would be
nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do run
another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?

Pretty much the same as the original self oscillating chopper, control
transistor (2N2222 etc) clamps the chopper base on overvoltage. The
control circuit can be simple as you like or complex as you need -
simple voltage divider is probably best if you sample from the end of
the ladder.
Thank you for not reading the question and avoiding what i asked for.



I chose to interpret the question as not being silly - the TV sweep
section is not designed for PWM (you might get away with burst mode
thogh).

It seemed more sensible to assume you were asking how to regulate the
voltage on the PSU which was designed for PWM in the first place.



Another thing I just remembered - a TV flyback unit is highly resonant,
that means you'd have to keep the scan yoke in circuit (and accomodate
the physical assembly on the bench) to keep the resonant system tuned.
Without resonance you don't get the full flyback EHT voltage.

Bench?? For this exercise, everything in the TV will remain except
the addition of my control and a filament disconnect (so that the CRT
passes no DC current).


mike October 19th 12 04:08 PM

How change color TV to adjustable HVPS?
 
On 10/19/2012 12:33 AM, Robert Baer wrote:
Ian Field wrote:


"Ian Field" wrote in message
...


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would
not
transmit.
Also, are enlarged parts showing horizontal section; T703 output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU
out of
an Amiga or somesuch - I'd turned the transformer around and
driving one
of the original secondaries with a low VCEsat power transistor to
get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit
- the
problem encountered the first time I powered up was a continuous arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this
basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it
would be
nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run
another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?

Pretty much the same as the original self oscillating chopper, control
transistor (2N2222 etc) clamps the chopper base on overvoltage. The
control circuit can be simple as you like or complex as you need -
simple voltage divider is probably best if you sample from the end of
the ladder.
Thank you for not reading the question and avoiding what i asked for.



I chose to interpret the question as not being silly - the TV sweep
section is not designed for PWM (you might get away with burst mode
thogh).

It seemed more sensible to assume you were asking how to regulate the
voltage on the PSU which was designed for PWM in the first place.



Another thing I just remembered - a TV flyback unit is highly resonant,
that means you'd have to keep the scan yoke in circuit (and accomodate
the physical assembly on the bench) to keep the resonant system tuned.
Without resonance you don't get the full flyback EHT voltage.

Bench?? For this exercise, everything in the TV will remain except the
addition of my control and a filament disconnect (so that the CRT passes
no DC current).


If I were gonna do it, assuming efficiency is no object, I'd regulate
by changing the DC volts going into the flyback.
Might even be able to do a first order approximation of pulse width
based on desired output voltage and close the DC volts loop around that
for regulation.

Robert Baer[_3_] October 20th 12 10:38 PM

How change color TV to adjustable HVPS?
 
mike wrote:
On 10/19/2012 12:33 AM, Robert Baer wrote:
Ian Field wrote:


"Ian Field" wrote in message
...


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Ian Field wrote:


"Robert Baer" wrote in message
...
Attached is a truncated version of the manual as the 2Megs would
not
transmit.
Also, are enlarged parts showing horizontal section; T703
output to
CRT is about 30KV.
Would be nice to have adjustment from around 10KV to full 30KV.

Thankx.


Do you actually need the full current that a CTV flyback stage can
generate 24kV at?

Years ago I was messing around with the transformer from the PSU
out of
an Amiga or somesuch - I'd turned the transformer around and
driving one
of the original secondaries with a low VCEsat power transistor to
get
high voltage from what had been the primary.

Apart from turning the transformer around, it was the same blocking
oscillator style self oscillating chopper as the original circuit
- the
problem encountered the first time I powered up was a continuous
arc
between the pins of the high voltage winding. It was neccessary to
complete the circuitry including the regulation loop for safe
operation.

If you don't need a vast amount of current at EHT voltage, this
basic
circuit driving a diode/capacitor ladder will do just fine.
I have no idea as to how much current these nominally supply to the
CRT; suppose it is maybe 1mA or so.
Current capability could decrease as voltage decreases but it
would be
nice to have nearly the same current capability as far down as 20KV
and then decrease in current capability.

I see no sense in ripping out the xfmr, building another supply do
run
another oscillator - why re-invent the wheel when it is there and
nicely round?


So,how could one vary the output voltage?

Pretty much the same as the original self oscillating chopper,
control
transistor (2N2222 etc) clamps the chopper base on overvoltage. The
control circuit can be simple as you like or complex as you need -
simple voltage divider is probably best if you sample from the end of
the ladder.
Thank you for not reading the question and avoiding what i asked for.



I chose to interpret the question as not being silly - the TV sweep
section is not designed for PWM (you might get away with burst mode
thogh).

It seemed more sensible to assume you were asking how to regulate the
voltage on the PSU which was designed for PWM in the first place.


Another thing I just remembered - a TV flyback unit is highly resonant,
that means you'd have to keep the scan yoke in circuit (and accomodate
the physical assembly on the bench) to keep the resonant system tuned.
Without resonance you don't get the full flyback EHT voltage.

Bench?? For this exercise, everything in the TV will remain except the
addition of my control and a filament disconnect (so that the CRT passes
no DC current).


If I were gonna do it, assuming efficiency is no object, I'd regulate
by changing the DC volts going into the flyback.
Might even be able to do a first order approximation of pulse width
based on desired output voltage and close the DC volts loop around that
for regulation.

That is what i finally determined; LTspice simulation is as follows:

Version 4
SHEET 1 880 680
WIRE 496 16 -48 16
WIRE 80 112 32 112
WIRE 176 112 160 112
WIRE 224 112 176 112
WIRE 240 112 224 112
WIRE 336 112 320 112
WIRE 416 112 336 112
WIRE 32 144 32 112
WIRE -48 160 -48 16
WIRE 416 176 416 112
WIRE 336 192 336 112
WIRE -48 256 -48 240
WIRE 32 256 32 224
WIRE 176 256 176 176
WIRE 304 288 304 160
WIRE 496 288 496 16
WIRE 496 288 304 288
FLAG 32 256 0
FLAG 416 256 0
FLAG 336 256 0
FLAG 176 256 0
FLAG -48 256 0
SYMBOL voltage 32 128 R0
SYMATTR InstName V1
SYMATTR Value 117V
SYMBOL res 64 128 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 10
SYMBOL res 400 160 R0
SYMATTR InstName R2
SYMATTR Value 404
SYMBOL cap 160 112 R0
SYMATTR InstName C1
SYMATTR Value 33µ
SYMBOL cap 320 192 R0
SYMATTR InstName C2
SYMATTR Value 50µ
SYMBOL voltage -48 144 R0
WINDOW 0 8 7 Left 2
WINDOW 3 -27 157 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 250 10n 10n 10n 1u 100u 5000)
SYMBOL nmos 224 160 R270
WINDOW 3 79 57 VRight 2
SYMATTR Value STP8NM60
SYMATTR InstName M1
TEXT -80 320 Left 2 !.tran 0 30m 0 1m


mike October 21st 12 07:41 AM

How change color TV to adjustable HVPS?
 
On 10/20/2012 1:38 PM, Robert Baer wrote:

That is what i finally determined; LTspice simulation is as follows:

Version 4
SHEET 1 880 680
WIRE 496 16 -48 16
WIRE 80 112 32 112
WIRE 176 112 160 112
WIRE 224 112 176 112
WIRE 240 112 224 112
WIRE 336 112 320 112
WIRE 416 112 336 112
WIRE 32 144 32 112
WIRE -48 160 -48 16
WIRE 416 176 416 112
WIRE 336 192 336 112
WIRE -48 256 -48 240
WIRE 32 256 32 224
WIRE 176 256 176 176
WIRE 304 288 304 160
WIRE 496 288 496 16
WIRE 496 288 304 288
FLAG 32 256 0
FLAG 416 256 0
FLAG 336 256 0
FLAG 176 256 0
FLAG -48 256 0
SYMBOL voltage 32 128 R0
SYMATTR InstName V1
SYMATTR Value 117V
SYMBOL res 64 128 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 10
SYMBOL res 400 160 R0
SYMATTR InstName R2
SYMATTR Value 404
SYMBOL cap 160 112 R0
SYMATTR InstName C1
SYMATTR Value 33µ
SYMBOL cap 320 192 R0
SYMATTR InstName C2
SYMATTR Value 50µ
SYMBOL voltage -48 144 R0
WINDOW 0 8 7 Left 2
WINDOW 3 -27 157 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 250 10n 10n 10n 1u 100u 5000)
SYMBOL nmos 224 160 R270
WINDOW 3 79 57 VRight 2
SYMATTR Value STP8NM60
SYMATTR InstName M1
TEXT -80 320 Left 2 !.tran 0 30m 0 1m

Is there a 1-minute overview on how to run this?
I haven't run spice in 20 years.
I downloaded/installed ltspiceIV.
Tried to import the netlist.
Got lots of errors when I tried to simulate it.
So, I made a schematic and exported the netlist.
Doesn't look anything like this format.
I musta downloaded the wrong simulator???

"ExpressPCB Netlist"
"LTspice IV Version 4.16t"
1
0
0
""
""
""
"Part IDs Table"
"Q1" "NPN" ""
"R1" "R" ""
"R2" "R" ""
"R3" "R" ""

"Net Names Table"
"P001" 1
"N001" 3
"P002" 5
"NC_01" 7
"0" 8
"NC_02" 9

"Net Connections Table"
1 1 1 2
1 2 2 0
2 1 2 4
2 4 2 0
3 1 3 6
3 3 1 0
4 2 1 0
5 3 2 0
6 4 1 0



mike October 21st 12 01:12 PM

How change color TV to adjustable HVPS?
 
On 10/20/2012 11:16 PM, flipper wrote:
On Sat, 20 Oct 2012 22:41:07 -0700, wrote:

On 10/20/2012 1:38 PM, Robert Baer wrote:

snip

Is there a 1-minute overview on how to run this?
I haven't run spice in 20 years.
I downloaded/installed ltspiceIV.
Tried to import the netlist.
Got lots of errors when I tried to simulate it.
So, I made a schematic and exported the netlist.
Doesn't look anything like this format.
I musta downloaded the wrong simulator???


The program is right. The problem is it isn't a netlist.

Just copy/paste the original source into notepad, save as
somename.asc (.asc extension), and then file open it with ltspice.

Double click on .asc works here but it's been so long since I first
installed ltspice that I don't remember if it did the association
itself or if I did manually.

Thanks, it didn't like .txt or .net or .cir. Never thought to try
..asc extension.
..asc fixed it.
Thanks,mike


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