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#1
Posted to alt.binaries.schematics.electronic
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How change color TV to adjustable HVPS?
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. |
#2
Posted to alt.binaries.schematics.electronic
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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. |
#3
Posted to alt.binaries.schematics.electronic
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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. |
#4
Posted to alt.binaries.schematics.electronic
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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? |
#5
Posted to alt.binaries.schematics.electronic
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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. |
#6
Posted to alt.binaries.schematics.electronic
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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 |
#7
Posted to alt.binaries.schematics.electronic
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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. |
#8
Posted to alt.binaries.schematics.electronic
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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)? |
#9
Posted to alt.binaries.schematics.electronic
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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. |
#10
Posted to alt.binaries.schematics.electronic
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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. |
#11
Posted to alt.binaries.schematics.electronic
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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. |
#12
Posted to alt.binaries.schematics.electronic
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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. |
#13
Posted to alt.binaries.schematics.electronic
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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. |
#14
Posted to alt.binaries.schematics.electronic
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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). |
#15
Posted to alt.binaries.schematics.electronic
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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. |
#16
Posted to alt.binaries.schematics.electronic
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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 |
#17
Posted to alt.binaries.schematics.electronic
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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 |
#18
Posted to alt.binaries.schematics.electronic
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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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