RGB cable pinout

Any idea someone?

You see a bold vertical line in in the 1084S_folded_image.jpeg photo?
Do you mean the rightmost pixels that look a bit brighter than white?

That might be the horizontal retrace starting a bit too early, just before having drawn the rightmost pixel.
I guess there must be an analog timeout circuit (like a capacitor and resistor/potentiometer) that will enforce horizontal retrace after approx 1/15000 seconds.
Did you check the service manual, maybe that's described there?

Yes, I'm talking about the rightmost bold bright line.

I have the schematics, the same I posted here in the first post. It's pretty detailed, however, I couldn't reach the exact point I need to measure in order to start the debug process and get to the root cause.
Another thing I want to mention related to this issue is that when adjusting the horizontal position POT, the only thing that moves is the left part of the screen, the right side stays stationery.
When tuning horizontal size however, both side moves.

It might be anything to do with the flyback change?
The old original one was "Philips AT 2079 37591" and the new one is "HR 7533".

Any hint the will help me move on with this debug process will be much appreciated.

Thanks!

x86_guy wrote on 2024-11-30, 15:54:

I have the schematics, the same I posted here in the first post. It's pretty detailed, however, I couldn't reach the exact point I need to measure in order to start the debug process and get to the root cause.
Another thing I want to mention related to this issue is that when adjusting the horizontal position POT, the only thing that moves is the left part of the screen, the right side stays stationery.
When tuning horizontal size however, both side moves.

This means the picture is always too much to the right. The range of the horizontal position pot ranges from slightly too much to the right to way too much to the right. As the horizontal position is controlled by the pot 3264 in conjunction with the resistors 3261 and 3262. The TDA2579 datasheet mentions that horizontal position can be adjusted by "forcing an external charge or discharge current into the capacitor of pin 14", which is exactly what that circuit is supposed to do. The allowed current in/out of that capacitor is +/-60µA, and if I understand the schematic correctly, that's about what the circuit is supposed to do. The junction between R3264 and R3262 is supposed to vary between 2.6 and 5.4V when you adjust the vertical position. If these voltages are way off, you should check these components. While you could try to change the values of R3261 and R3262 to increase the range of the horizontal position pot, this is not recommended, as it seems the current design already covers the whole range of horizontal position adjustment allowed in the datasheet of the TDA2579 synchronization chip.

Furthermore, you should know that the TDA2579 uses feedback from the flyback primary to correct for delays in the horizontal drive stage (which will affect horizontal position as well), and falls back to a default mode if the feedback on pin 12 is missing. The datasheet calls for a typical minimum pulse amplitude of 1V at that pin, with a limit of 12V. While I suspected that the replacement flyback transformer might be important here, I don't think it is. The idea of that circuit is that the collector of the horizontal drive transistor T7512 is close to ground while the transistor is on, and higher than B+ (i.e. more than 128V) when the transistor if off. Resistors R3271/R3272 make a 1:100 divider, which divides 128V to 1.28V. Directly after turning off T7512, you will get additional voltage from the inductive flyback, so the 1V threshold should be crossed - unless the trace from flyback pin 5 to R3271 is broken or R3271 is open.

I hope these two pointers help you find the issue why the picture position can not be adjusted correctly.

Oh, I had somehow missed the schematic linked in 1st post, and only saw the cable wiring diagram in 2nd post.

mkarcher does apparently know much more about analog monitors than me, and you do probably know more than me, too. I agree that it looks as if the picture is too much to the right, and that it probably gets truncated at the right screen edge, or that the horizontal retrace jumps in shortly before reaching the screen edge.

To get a better idea if there are any missing truncated pixels, it might help if you could look at a full picture instead of the (mostly) blank white amiga boot screen, like a bootable game disk, or workbench disk, or some nes/snes/psx gaming console with composite output.

Ah, no. The monitor is rgb only? Then forget about using composite consoles for testing (but most have rgb outputs, too).

x86_guy wrote on 2024-10-26, 22:54:

The issue is, the screen is folded a bit at the sides, and I can't get it fixed using the H-position/H-size controls. I can get only one of the sides without folding, but then the other side is folded. The folding looks like a bold vertical line and the very left/right side of the image (it may have another expression?).

Flyback transformers are not made equal and many "replacements" are only close but not identical to the OEM parts. Also when it goes bad it will often take out HOT along with it, and/or nearby parts. You need to double-check everything in the drive section to be sure you can operate the monitor safely. Basically test everything connected to the collector to make sure it's still in-spec. The driving side (HOT base and toward the secondary of pulse transformer) is also worth checking although if it produces nice picture it's probably OK. But better safe then sorry.

Check the parts that are connected to the yoke. Anything connected to pin 5 of the flyback but also the other side of the yoke windings as well. Look for cracked solder joints as well. If any of the diodes here failed I would expect to see some sort of non-linearity in the image but who knows, the IC driving horizontal might be able to compensate for some of it. Sometimes the caps can fail short but then open when power is removed, and kinda work afterwards but with a reduced capacity. You don't always spot it right away, even at the HOT collector not all faults results in smoked parts. If in doubt desolder the part from circuit to test it. Unplugging the yoke might help to isolate parts of the circuit for testing as well.

Sometimes the new flyback is sufficiently different that you will have to change some part values in the horizontal width or linearity control, but before you start doing that please check it actually gets the required -27V as per schematic. If it's out of spec then possibly the replacement flyback requires some different parts on pin 10. All in all I'd say this if you are this close you will get there eventually.

Deunan wrote on 2024-12-02, 00:03:

Sometimes the new flyback is sufficiently different that you will have to change some part values in the horizontal width or linearity control, but before you start doing that please check it actually gets the required -27V as per schematic. If it's out of spec then possibly the replacement flyback requires some different parts on pin 10. All in all I'd say this if you are this close you will get there eventually.

I don't think the -27V is the primary issue, as the width control does reportedly work as intended, while the position/phase control does not have sufficient range.

Thinking more about it, there may be two reasons why the position is too far to the right. In my previous post, I focussed on the horizontal drive signal generated by the TDA2579, assuming it terminates the horizontal scan cycle early, and looking for stuff that influences the phase of the horizontal oscillator. This is because we obviously see that the drive voltage to the horizontal yoke coil is insufficient near the right edge of the picture, so the ray does no longer sweep at the desired speed. One reason for insufficient drive voltage is the HOT turning off, as turning off the HOT will stop providing the sweep-to-the-right voltage and instead start applying the retrace voltage. But there might be another reason why the horizontal yoke is insufficiently driven near the right edge: If the replacement HOT has a lower inductance, the HOT might saturate near the right edge of the picture, and thus fail to provide a stable deflection voltage. There is a "safe" test point for the output voltage of the HOT - that's pin 12 of the TDA2579, which gets the HOT ouptut divided by 100. Assuming the OP has a scope and knows how to safely scope inside a monitor, it would be helpful to verify the scope image at test point 11. If the HOT saturates, the bottom line between the retrace spikes will start to rise at the end of the bottom line, instead of staying flat until the retrace spike starts. A more simple test to get an idea whether we deal with saturation if the HOT is reducing the B+ voltage. If the HOT is saturating, tuning B+ down is supposed to mitigate the issue, as a lower B+ voltage causes a slower raise of the collector current (and generally a less wide picture). As reducing B+ will directly affect the +9 and +28 voltages, which do not have their own post-regulators and it might also provide insufficient voltage for the +5 and +12 regulators, I do not recommend dropping B+ to less than 120V, but this should be enough to be able to see whether HOT saturation is related to the issue and then decide what trouble-shooting path to continue.

According to the schematic, circuit ground of the monitor is connected to mains earth, so probing with a ground-referenced scoped seems to be possible without any additional danger. The usual cautions about probing in a live circuit that contains AC and DC voltages way above 100V still apply, of course.

Hi all,
Thanks for the feedback and sharing your thoughts.

I've measured a couple of components and signals, so far this is what I got:

3261 = 14.8k
3264 = 9.24k
3262 = 4.65k
3263 = 21.7k
2262 = 101.2nF, ESR = 75.78 OHM at 1kHz

3271 = 1.15M
3274 = 9.93k

3262/3264 Junction = 2.04V -> 5.06V (range)
-27V rail (Measured on 3534) = -25.7V

I also measured TP11, TP12, TP13 using a scope - screenshots below:

For the 128V rail - I adjusted this voltage in the past. If I remember correctly, the issue hasn't solved with lower voltage than 128V. I can re-test later.
However, interesting thing happened while adjusting this rail - When I got over 128V, I can't recall the exact voltage, the flyback started producing a high pitch noise an the CRT stopped displaying.
I immediately turned off the monitor, lowered the voltage then fired again - problem solved.

The same symptom of high pitch noise and CRT turns off is the exact thing happened with the original flyback, but in this case I wasn't aware that the 128V rail can directly impact the flyback and produce this issue. I didn't try to adjust it then, so it might be out of spec. This leads me to wonder - Is it possible that the old flyback is still good? Any way to test it?

I'm able to do more testing - if needed , please let me know.

x86_guy wrote on 2024-12-04, 00:40:

I've measured a couple of components and signals, so far this is what I got: […]
Show full quote

I've measured a couple of components and signals, so far this is what I got:

3261 = 14.8k
3264 = 9.24k
3262 = 4.65k
3263 = 21.7k
2262 = 101.2nF, ESR = 75.78 OHM at 1kHz

3271 = 1.15M
3274 = 9.93k

3262/3264 Junction = 2.04V -> 5.06V (range)
-27V rail (Measured on 3534) = -25.7V

Both ends of the range at 3263/3264 are lower than I expected. This may be due to a miscalculation, a wrong assumption about the detailed behvaiour of pin 14 or excessive leakage from pin 14 to ground. On the other hand, it's not that far off that I would chase that path right now. The service manual show 2.7V nominal at pin 14, which is within your range, but near the very low end of my expectation. I guess this is fine.

x86_guy wrote on 2024-12-04, 00:40:

I also measured TP11, TP12, TP13 using a scope - screenshots below:

The TP12 and TP13 screenshots looks fine.

On the other hand TP11 is worrysome in my oppinion. There is a clear negative spike at the end the horizontal retrace impulse that's not in the service diagram. A negative spike there will most likely push the picture too much to the right, which is the symptom we are chasing. As the voltage at TP11 is supposed to be 1:100 of the voltage at TP15, the spike is most likely present at TP15 as well. Looking at the expected diagram, I find the TP15 voltage to be even higher than 100 times the TP11 voltage (over 1000 volts instead of just 282V), so this is likely due to the load at TP11 when you scope it with a 1:1 probe. Do not try to scope TP15 unless you have a 100:1 or 1000:1 probe and are confident how to use it!

Seing -560mV at TP11 implies at least -56V at TP15, probably more like -150V. Negative voltages that high are not supposed to occur at that point, because they should be pulled to ground via diodes 6517 and 6518. So I recommend to check these diodes next.

x86_guy wrote on 2024-12-04, 00:40:

For the 128V rail - I adjusted this voltage in the past. If I remember correctly, the issue hasn't solved with lower voltage than 128V. I can re-test later.
However, interesting thing happened while adjusting this rail - When I got over 128V, I can't recall the exact voltage, the flyback started producing a high pitch noise an the CRT stopped displaying.
I immediately turned off the monitor, lowered the voltage then fired again - problem solved.

The TP11 diagram doesn't show the sign that +128V should be lowered. No need to re-test it. The issue you got while 128v was high might be due to breakdown or arcing in some component, so it was definitely correct to shut down the monitor as fast as possible. As this situation may cause damage, do not willfully repeat that experiment.

I concur that there should not be any significant negative spikes at collector of 7512 (BU508A). And I'm going to repeat: DO NOT measure anything here, at pin 5 of the flyback, with power applied. The spikes here will kill most electronic equipment very quickly.

I'v already mentioned that after HOT of flyback misbehaving all the parts here need to be checked. Sooner rather than later because all are critical, and HOT wil die when abused. And since it usually dies short the flyback will get destroyed as well. In other words any lazyness will be "rewarded" with expensive repair.

The weird behaviour of the monitor when +128 is adjusted might be related to X-RAY protection kicking in. It shouldn't really but since the PSU is self-oscillating rather than PWM IC based it might just be able to restart quickly and generate that weird effect. An IC based PSU would typically back off for a split second or so, this results in "ticking" sound when it tries to restart but is shorted. I'd advise against any experiments to try and figure out what is going on since such unstable operation is certainly not good for the HOT and flyback, but some measurements can be taken. Schematic shows voltage at capacitor 2547 to be 23.4V (this one can be measured) and this is really the upper end of it. Anything more will trip the circuit. If this circuit is so close to the balance point then even a dirty 3414 pot used to regulate the +128V line might be able to trip it. So not necessarily an issue as such if the voltage can be set properly otherwise.

Which brings us to the question if the previous flyback could still be good, actually. You can only test it for obvious shorts and breaks without a special test equipment. There are some tools that can test such transformers for winding shorts but in my experience these rarely die with such a fault. It's either good or clearly bad. You can figure out the internal connection using the schematic but keep in mind testing the HV section is difficult due to the built-in diodes. These have pretty high drop, so any voltage below 100V might not even get through. On the other hand don't try using higher voltage for testing without some carefully selected resistor to limit the test current - the diodes are HV but can only take low current, less than 1mA on average. You don't want to damage those.

A typical damage for a flyback transformer is an obvious short from HV winding to the primary or other secondaries. This can be discovered with a typical universal ohm meter. Another common fault is internal short from the "bottom" of HV winding, which would be pin 7 here, to any nearby pins. Pin 7 should read open to everything else on the transformer using a standard meter. Since you have it desoldered look for any obvious signs of an arc (or crack in plastinc) near pin 7. That's how a lot of TV flybacks die for some reason. Other than that you can only properly test the transformer in the circuit.

mkarcher wrote on 2024-12-04, 06:46:

The TP12 and TP13 screenshots looks fine.

On the other hand TP11 is worrysome in my oppinion. There is a clear negative spike at the end the horizontal retrace impulse that's not in the service diagram. A negative spike there will most likely push the picture too much to the right, which is the symptom we are chasing. As the voltage at TP11 is supposed to be 1:100 of the voltage at TP15, the spike is most likely present at TP15 as well. Looking at the expected diagram, I find the TP15 voltage to be even higher than 100 times the TP11 voltage (over 1000 volts instead of just 282V), so this is likely due to the load at TP11 when you scope it with a 1:1 probe. Do not try to scope TP15 unless you have a 100:1 or 1000:1 probe and are confident how to use it!

Seing -560mV at TP11 implies at least -56V at TP15, probably more like -150V. Negative voltages that high are not supposed to occur at that point, because they should be pulled to ground via diodes 6517 and 6518. So I recommend to check these diodes next.

Deunan wrote on 2024-12-04, 18:52:

I concur that there should not be any significant negative spikes at collector of 7512 (BU508A). And I'm going to repeat: DO NOT measure anything here, at pin 5 of the flyback, with power applied. The spikes here will kill most electronic equipment very quickly.

I tested 6517, 6518 diodes. Both are fine with no reverse leakage.
6518 diode - Vf = 543mV
6517 diode - Vf = 590mV

I understand that the undershoot spike shouldn't exist on TP11, what else can lead to this behavior other than those diode?

mkarcher wrote on 2024-12-04, 06:46:

The TP11 diagram doesn't show the sign that +128V should be lowered. No need to re-test it. The issue you got while 128v was high might be due to breakdown or arcing in some component, so it was definitely correct to shut down the monitor as fast as possible. As this situation may cause damage, do not willfully repeat that experiment.

Deunan wrote on 2024-12-04, 18:52:

The weird behaviour of the monitor when +128 is adjusted might be related to X-RAY protection kicking in. It shouldn't really but since the PSU is self-oscillating rather than PWM IC based it might just be able to restart quickly and generate that weird effect. An IC based PSU would typically back off for a split second or so, this results in "ticking" sound when it tries to restart but is shorted. I'd advise against any experiments to try and figure out what is going on since such unstable operation is certainly not good for the HOT and flyback, but some measurements can be taken. Schematic shows voltage at capacitor 2547 to be 23.4V (this one can be measured) and this is really the upper end of it. Anything more will trip the circuit. If this circuit is so close to the balance point then even a dirty 3414 pot used to regulate the +128V line might be able to trip it. So not necessarily an issue as such if the voltage can be set properly otherwise.

Which brings us to the question if the previous flyback could still be good, actually. You can only test it for obvious shorts and breaks without a special test equipment. There are some tools that can test such transformers for winding shorts but in my experience these rarely die with such a fault. It's either good or clearly bad. You can figure out the internal connection using the schematic but keep in mind testing the HV section is difficult due to the built-in diodes. These have pretty high drop, so any voltage below 100V might not even get through. On the other hand don't try using higher voltage for testing without some carefully selected resistor to limit the test current - the diodes are HV but can only take low current, less than 1mA on average. You don't want to damage those.

A typical damage for a flyback transformer is an obvious short from HV winding to the primary or other secondaries. This can be discovered with a typical universal ohm meter. Another common fault is internal short from the "bottom" of HV winding, which would be pin 7 here, to any nearby pins. Pin 7 should read open to everything else on the transformer using a standard meter. Since you have it desoldered look for any obvious signs of an arc (or crack in plastinc) near pin 7. That's how a lot of TV flybacks die for some reason. Other than that you can only properly test the transformer in the circuit.

The 128V adjusting trimmer was rusty and in poor condition when I first go this monitor, like many other trimmers on this board . After I made some deep cleaning to this board, I replaced the bad trimmers (only variable resistor type of trimmers).
I don't know what was the 128V voltage when I first started the monitor, But after the flyback showed sings of dying, I replaced it and adjusted to an accurate 128V (I wasn't aware of this voltage before).

I tested the old flyback now. Pin 7 isn't shorted to any other pin. However, I get a resistance of 28.5Ohm between Pins 9,10 and 3,5. Per flyback datasheet, those pins need to be totally isolated, so I guess this flyback sure is bad?
The new flyback reads open loop between those pins.

Deunan wrote on 2024-12-04, 18:52:

I'v already mentioned that after HOT of flyback misbehaving all the parts here need to be checked. Sooner rather than later because all are critical, and HOT wil die when abused. And since it usually dies short the flyback will get destroyed as well. In other words any lazyness will be "rewarded" with expensive repair.

I made some measurements on this area and caught a bad cap.
While cap 2515 should be 1uF, the actual measurement was 250nF, with ESR of 320Ohm. When I took it off I saw an electrolyte leakage at the bottom (photo attached).
Do you think that this cap can impact image horizontal position according to the schematics?

x86_guy wrote on 2024-12-10, 00:09:

I understand that the undershoot spike shouldn't exist on TP11, what else can lead to this behavior other than those diode?

Your measurement setup. Basically without directly probing TP15, which you can't without a specialized HV probe, you can't be 100% sure of what is going on there. TP11 is very high impedance circuit, the signal of interest arrives via 1M resistor. Even small capacitance and inductance of the scope probe is going to introduce changes. Add to that the fact this is a feedback circuit, I would not be surprised if merely touching the TP11 with the probe tip shows a visible change on the screen. So this is a good starting point to investigate but not a proof of a problem in other words.

x86_guy wrote on 2024-12-10, 00:09:

I tested the old flyback now. Pin 7 isn't shorted to any other pin. However, I get a resistance of 28.5Ohm between Pins 9,10 and 3,5. Per flyback datasheet, those pins need to be totally isolated, so I guess this flyback sure is bad?
The new flyback reads open loop between those pins.

That would be my assumption, a short inside. In some cases it might be just an autotransformer-like setup to generate additional voltages directly from primary (it is very common for so-called boost voltage) but not here. Pin 9 is connected to GND so there is no way we can have this winding be a part of the primary, which is directly connected to +128V. It's dead I'm afraid.

x86_guy wrote on 2024-12-10, 00:09:

I made some measurements on this area and caught a bad cap.
While cap 2515 should be 1uF, the actual measurement was 250nF, with ESR of 320Ohm. When I took it off I saw an electrolyte leakage at the bottom (photo attached).
Do you think that this cap can impact image horizontal position according to the schematics?

Yup. So first keep in mind the residue of the leak is conductive and corrosive, inspect the PCB and clean everything around this cap. The voltage spikes here will cause you a lot of problems and possibly another blown transformer/HOT otherwise. It's actually the horrible ESR of this cap that is the issue, more than the loss of capacity. From schematic this is a bypass circuit for the 2519 cap, which is only 560nF (but that is well enough for the 15kHz frequency) with the 6514/6515 diodes helping the yoke coils to discharge its magnetic field into current much faster. This high ESR might cause the coil to retain some of the field and never fully "reset" on retrace, and your image shift problem.

If possible replace this cap with low-ESR variant of good quality (some known brand prferably, like Nichicon or Panasonic). This is not super critical but could help. But if you can't find low-ESR 1uF/250V then any good brand cap should do. In general the bigger the cap, the lower the ESR so if you see a replacement look at the size. You don't want it much smaller than the original, unless there is no choice. A bit smaller is OK, there have been some improvements in the tech.

x86_guy wrote on 2024-12-10, 00:09:

I tested 6517, 6518 diodes. Both are fine with no reverse leakage.
6518 diode - Vf = 543mV
6517 diode - Vf = 590mV

OK, this looks fine. Are the diodes still the original type? They are supposed to be a BYV95C and a BY228, which are both quite fast diodes. If someone replaced a broken diode here by a 1N4007, this would be bad.

x86_guy wrote on 2024-12-10, 00:09:

I understand that the undershoot spike shouldn't exist on TP11, what else can lead to this behavior other than those diode?

I'm with Deunan here: The negative spike might be an artifact depending on the grounding setup and the kind of probe you are using to measure at TP11. The spikes might not acutally be there at all. While Deunan is correct that probing TP11 might distort TP11 to cause some distortion (like shifting the picture a bit), it is no closed-loop amplifier in which any distortion to the feedback may set up osciallation and other weird behaviour. I don't think the negative spikes are generated by the circuit due to your probing.

x86_guy wrote on 2024-12-10, 00:09:

I made some measurements on this area and caught a bad cap.
While cap 2515 should be 1uF, the actual measurement was 250nF, with ESR of 320Ohm. When I took it off I saw an electrolyte leakage at the bottom (photo attached).
Do you think that this cap can impact image horizontal position according to the schematics?

That cap is an integral part of the horizontal deflection circuit. The capacitor is clearly broken and the two equally bad measurements you took show only a part of the actual behaviour of the component. I have no reason to be confident that the capacitor isn't also high-leakage, might break down at voltages way below the indicated 250V or just develop other kinds of non-linear behaviour. The measurements might even be completely off if the tester you used assumes a "properly behaved capacitor" and makes assumptions on other parameters like the leakage. So yes: Do change that cap, and don't spend much time worrying about what the specific values you measured mean beyong: "That cap is gone".

If I understand the circuit correctly, capacitor 2515 is charged via resistor 3515 during the flyback pulse, so pin 1 at the yoke connector M4 is more negative than pin 5 at the flyback. During the horizontal sweep, diodes 6515 and 6514 as well as capacitor 2515 are in the current path that creates the increasing yoke current to push the beam to the right. Anything that impedes current flow, like a high ESR of that capacitor or the capacitor being (dis)charged too quickly, so the negative voltage at M4/pin1 is not as strong as intended over the whole scan line can prevent sufficient current build-up in the yoke to push the beam to the right edge.

I ordered a couple pieces of this cap.
Once I get it, I'll replace the old one and let you know how it goes.

Thank a lot for the help!

I replaced the capacitor - it didn't help 😒

What I still don't understand is: Are you really using the white boot screen with the floppy symbol for testing? That looks completely unsuitable to me. Don't you have a workbench disc, or game disc, something with a real picture? Or are you an expert on Amiga hardware and know exactly how the white boot screen should look like on that particular monitor?

I am not too familar with the amiga appearance, I assume that the boot screen consists of a bitmap with white pixels, surrounded by a black or white (?) screen border, so I couldn't tell which of the pixels on you photo are part of the bitmap or border. And I assume the floppy and/or hand is supposed to be centered in the middle of the screen, with the same amount of white pixels on each side, but I am just guessing there. And of course, all pixels should have the same width, but it's impossible to tell if that's the case with all-white background on your photo.

Doing an image search for Commodore 1084S-P1, it seems the games do usually have a screen border about the size of the black region on your photo. I have also found a screenshot of the v1.3 bootscreen, which seems to have the whole screen including border filled with white pixels, unlike as on your photo... but that screenshot has a gray slider on the floppy symbol, why is yours having a red slider???

x86_guy wrote on 2024-12-24, 23:23:

I replaced the capacitor - it didn't help 😒

Pity, I was rather hoping it would do the job. Because there isn't much else in there than can cause that, except the whole size control circuit perhaps. This is where pincushion correction is injected, which also looks bad on your shots.

First, a question: In your opening post you've wrote that all the potentiometers on the back were replaced but you also gave the values: "2x10k, 1x220k". Which one is the 220k? Because AFAIK all three of them should be 10k.
Second, can you measure the voltage on the 1uF capacitor 2526, it's connected to that /!\ marked resistor 3526 on the schematic, right next to the flyback transformer. There shouldn't be any nasty voltages on this side of the circuit, the schematic shows 13V4 being the expected voltage. I am interested in what voltage do you get at both opposite ends turning the H-size control pot. I would expect this to be between about 1V at minimum and 25V or so at maximum.