• Please review our updated Terms and Rules here

SE/30, wobbly horizontal display, worsened by HDD activity

Can also add full boot from floppy to 6.0.8 verified.
Have also replaced C9 (1000uF/16V) on analog board.
No change in the vertical deflection behaviour.
 
Some additional observation re V deflection:
The raster seems to start slow and too early, and then increase in speed at the end, so the image is increasingly compressed.
 
Use the previous schematic and go through the vertical drive circuitry since you have vertical foldover.

Points of interest would be the height potentiometer, measure its current resistance and write it down. Then hose it down with Deoxit Gold and wipe it back and forth several times to clean it. Try and get it close to what the value was before. If the screen comes back, adjust it as necessary. I'd recommend doing this service to all of the POTs, because they tend to get oxidized internally and cause problems.

Another would be more bad solder joints. Tap the back of the analog board with the insulated end of a screwdriver. If the screen starts glitching, there are joints that need to be repaired.

Also check the yoke connector for cracks or bad connections. You may also want to ohm out the vertical deflection coil with it disconnected from the analog board to see if its measuring correctly, it should be around 8 ohms.

Check all of the passives in the vertical section. Resistors, diodes, etc. You may try poking the resistors while measuring them to see if they change in value or exhibit strange behavior. It's not uncommon for carbon composition resistors to develop cracks internally and arc out, causing the resistor to drift in value. Heat and cold can also cause wild swings in value of a bad resistor, or even cause them to go open entirely.

Another possibility is the SE/30 logic board itself. The board could be sending out a bad signal that causes the wonky behavior. If you have another working SE or SE/30 board, you may try those and see if the problem persists.
 
Thanks!
I forgot to mention that I have given "all" points (may have missed one or two) on the analog board fresh solder.
They did all look good, but better to be sure.
I've verified the Hdef coil (8.8-ish ohm according to my not-a-fluke meter).
Height pot meter was stable across its range. Was set fairly low to begin with (almost fully clockwise).
Swapped the SE/30 main board with my SE board.
Trouble on PSU or analog board verified. Foldover remained.

Will need to verify the passives and such on the analog board.
I have a hunch C2 or C7 (both 100uF/16V) close to the TDA circuit may be the culprit.
C9 as mentioned has already been replaced after the current issue appeared. Measured fine, but not worth the trouble.
Also, this may be the PSU 12V sweep being unstable?
 
If you suspect the 12v Sweep rail to be bad, you can put an oscilloscope on it and measure the ripple. I don't know what spec Sony used, but the ATX spec is good to go by, no more than 120mv of ripple on the 12v Sweep.

If you don't have an oscilloscope, you can use a multimeter in AC mode and measure the rail. If you see any sort of AC voltage, then there's a problem.
 
I’ve now practically recapped the analog board, save for the two axials and C19 10uF/160 which I don’t have in stock.
No change.
Also, all Vdef resistors and diodes check out.
No idea about those weird glass capacitors though.
Low ripple on all lines from the PSU also, below 100mV according to my dmm (again, not fluke).
I do have a hunch that C19 is a part of the problem though, although related to the neck circuit.
Out of circuit, it has an ESR of about 1.5 ohm, not too bad, but I believe it is somehow critical that it has a lower ESR than that.
I’ve read that vertical foldover is often blamed on a "charge pump" cap failing and that they’re often low-ish uF and high Voltage. Sounds very familiar.
Is C19 in this circuit a charge pump?

Also included is a screenshot of 6.0.8 booted. Weird foldover indeed!
IMG_3101.jpeg
 
Thanks for avoiding a red herring!
What I’ve noticed is that the first lines of the display is upside down.
It looks like it starts drawing before the beam has returned to the top.
I’m starting to suspect the TDA1170 now.
 
Well, replaced with a NOS TDA1170N after two weeks of waiting for it to arrive.
No change.
Replacing CR1 (1n4001) next. Measures fine according to a transistor tester, but may have become leaky.
 
Thought I had added the solution here, but apparently I didn't.
Got some help over at 68kmla.
R7 and R8 on the analog board was shorted by a solder bridge during reflowing.
Removing the bridge solved the vertical issue.
 
trondl said:
Thought I had added the solution here, but apparently I didn't.
Got some help over at 68kmla.
R7 and R8 on the analog board was shorted by a solder bridge during reflowing.
Removing the bridge solved the vertical issue.
Click to expand...
What problems remain?
 
JDW said:
What problems remain?
Click to expand...
I think all is fixed for now. Still a bit wobbly in the lower right side of the display during long HDD seek tests, but this is not a problem in regular usage.
Definitely better now after recapping the analog board.

Now onto the slightly more unstable SE repair…
 
  • Like
Reactions: JDW
You must log in or register to reply here.
Back
Top