PEIC Monitor Vertical Size Too Small?

TR604 and TR605 tested fine :( I keep hoping it is something!!!!

@Tugce open to suggestions....

C610 does not look bad. It is a little polyester cap.
I would check the component connected to the base of TR605 and the two diodes on the right side by the base of TR 706 (cannot really read the part numbers on the schematic)
 
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I would check the component connected to the base of TR605 and the two diodes on the right side by the base of TR 706 (cannot really read the part numbers on the schematic)
The two diodes are CR601 and CR707. Both tested fine.

I also tested R617. Fine.

The part on the base of TR605 is TH601. In practice, R622 and TH601 are swapped vs. what the schematic shows. R622 tested fine.

I put it all back together and back in the game. At least I did not make things worse. I can adjust the pot and it gets smaller but maxed out it won't get larger.

Here is an updated picture of everything I have tested.
 

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The two diodes are CR601 and CR707. Both tested fine.

I also tested R617. Fine.

The part on the base of TR605 is TH601. In practice, R622 and TH601 are swapped vs. what the schematic shows. R622 tested fine.

I put it all back together and back in the game. At least I did not make things worse. I can adjust the pot and it gets smaller but maxed out it won't get larger.

Here is an updated picture of everything I have tested.
Maybe the drive for the beam adjustment is broken.

The coils driving the X and Y need a certain range of currents. I would check if the beam deflection reaches the edge of the screen. Probably the drivers have lost gain over the years or the components have drifted so they can't reach the desired ranges anymore.

I would make sure all the BJTs are good first, including the complementary driver circuit. If you check the deflection current/voltage you can see if it is saturating early. You can look at the coil driver signal and the signal at each stage of the driver going backwards. You might be able to see for example a saturated signal before/after one of the drivers.
 
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Maybe the drive for the beam adjustment is broken.

The coils driving the X and Y need a certain range of currents. I would check if the beam deflection reaches the edge of the screen. Probably the drivers have lost gain over the years or the components have drifted so they can't reach the desired ranges anymore.

I would make sure all the BJTs are good first, including the complementary driver circuit. If you check the deflection current/voltage you can see if it is saturating early. You can look at the coil driver signal and the signal at each stage of the driver going backwards. You might be able to see for example a saturated signal before/after one of the drivers.
Thanks for the ideas.

Thoughts on how I would test these with a multimeter? I suspect it might be hard.

What components that I haven't tested would you recommend I test?
 
Thanks for the ideas.

Thoughts on how I would test these with a multimeter? I suspect it might be hard.

What components that I haven't tested would you recommend I test?
I would first check TR 706. I will post a few more suggestions when I have access to a higher quality schematic.

There might be a way to test it, but not as easy as just testing the components as you suspected. However, you might need to do that for understanding drift.
 
@Tugce - attached an image. Hopefully this is higher quality.

I will test TR706.

Yes, this is better. I would check TR705 with 706 to start with as well. And check VR-I pot shown on the top part of the schematic.

I can also write out the steps for how to potentially test saturation with a multimeter.
 
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TR706 is fine.

I can check TR705 next.

Hmmmm. Interesting about the VR-1 pot. I'll check that out...
 
One thing I did notice is that cap C606 is listed as 22uf in the schematic but I originally had a 2.2uf there and the cap kit I got had 2.2uf as well. This was due to the fact that there was a 2.2uf cap in that spot when the cap kit was created.

See - https://forums.arcade-museum.com/threads/another-monitor-id-question.493377/

I had hoped that maybe the schematic was right. Anyway, I put a 22uf in and it made things worse. Back to the 2.2uf

This thing is killing me.
 
One thing I did notice is that cap C606 is listed as 22uf in the schematic but I originally had a 2.2uf there and the cap kit I got had 2.2uf as well. This was due to the fact that there was a 2.2uf cap in that spot when the cap kit was created.

See - https://forums.arcade-museum.com/threads/another-monitor-id-question.493377/

I had hoped that maybe the schematic was right. Anyway, I put a 22uf in and it made things worse. Back to the 2.2uf

This thing is killing me.
It makes sense that it got worse when you changed it to 22uF - I assume it was vertically even narrower than it was before? Given the impedance of that capacitance is 1/j(omega)C, when you increase the C by 10x, you reduced the impedance by that amount.

The bias of TR602 is set through that branch with C606 and resistive divider (R612/R612+R607+R631). So that gives you a clue that the biasing of TR602 is currently not right.
 
It makes sense that it got worse when you changed it to 22uF - I assume it was vertically even narrower than it was before? Given the impedance of that capacitance is 1/j(omega)C, when you increase the C by 10x, you reduced the impedance by that amount.

The bias of TR602 is set through that branch with C606 and resistive divider (R612/R612+R607+R631). So that gives you a clue that the biasing of TR602 is currently not right.
If that change made it narrow, let me suggest something to try.
 
The change didn't directly make it more or less narrow. It completely screwed up all the colors, brightness, etc. so all the pots need to be readjusted to even get a picture that I can make out what is happening.
 
The change didn't directly make it more or less narrow. It completely screwed up all the colors, brightness, etc. so all the pots need to be readjusted to even get a picture that I can make out what is happening.
If you have extra components, I would be curious to see if you replace R612 with ~20K instead of 56K, what happens to the picture. That might solve the saturation problem. If it helps, then we can probably identify which stage is the problem from there.
 
If you have extra components, I would be curious to see if you replace R612 with ~20K instead of 56K, what happens to the picture. That might solve the saturation problem. If it helps, then we can probably identify which stage is the problem from there.

If you have extra components, I would be curious to see if you replace R612 with ~20K instead of 56K, what happens to the picture. That might solve the saturation problem. If it helps, then we can probably identify which stage is the problem from there.
Trying that wouldn't harm the component since you would actually reduce the bias of TR602.
 
If you have extra components, I would be curious to see if you replace R612 with ~20K instead of 56K, what happens to the picture. That might solve the saturation problem. If it helps, then we can probably identify which stage is the problem from there.
The closest I have on hand is 10K. Would that work?
 
The closest I have on hand is 10K. Would that work?
It might work but probably at the edge since you will be reducing the voltage by >5x across the base of TR602. While you reduce saturation, you will probably reduce the gain significantly for 10K case. I would try 10K first and let me know what you see/vertical range, if not, you can solder them in series?
 
Some updates (I am sure people are glued to this thread)

R612 - we have put in now a 5.6K resistor and the picture is now pretty much all the way wide. Not the fix I want but we are at least getting closer.

Tested the following resistors and all were fine:
R604
R605
R609
R617
R619
R620

VR-I pot fine

I am going to buy new transistors for TR601 and TR603. They tested fine with the multimeter but this does not test their operation. @Tugce can explain better :)
 
Some updates (I am sure people are glued to this thread)

R612 - we have put in now a 5.6K resistor and the picture is now pretty much all the way wide. Not the fix I want but we are at least getting closer.

Tested the following resistors and all were fine:
R604
R605
R609
R617
R619
R620

VR-I pot fine

I am going to buy new transistors for TR601 and TR603. They tested fine with the multimeter but this does not test their operation. @Tugce can explain better :)
We think that one of the transistor outputs are saturated due to drift in components and cannot reach the desired ranges anymore in large signal, which means that we had to work with that lower headroom for the signal amplification/oscillator output.

So as the first thing, we changed R612 since that is used for biasing T602. Given that R612, R607, and R631 are in series, the voltage drop across R612 through the resistive divider is given in the attached document (didn't draw the entire circuit - just for the base biasing of T602). By lowering R612 from 56K to initially 10K and then to 5.6K, we reduced the base biasing of T602. That allowed us to operate in the more linear region of the BJT amplifier around the new quiescent bias point, hence reduced the saturation of the output.
 

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