Apple IIgs flickering / fading video (and/or no video at all). Bad caps or something else?

[Huxley]

Hi all!

My trusty Apple IIgs (ROM1) is suddenly a lot less trusty than it used to be. I've noticed that recently the image on my AppleColor RGB Monitor (the IIgs monitor) has been flickering, so I had it professionally recapped and refurbished by a legit CRT expert (Andy King of the CRT Database website). Based on his post-recap testing using different video source, I'm confident that the monitor works fine now.

HOWEVER: the flickering is now so bad that the system is basically unusable - it will work fine for a while, and then start flickering, and as the flickers get more intense, the image gets dimmer and dimmer, until it's totally black (or so faint that it's barely visible). This state will persist after reboots, and the only way to get it to kinda/sorta work again is to power the IIgs down and let it sit for 20+ minutes - then (sometimes) it'll run as normal for a while. I don't feel any unusual heat coming off the machine, for what that's worth.

The IIgs has an AppleSqueezer accelerator installed along with a LANceGS ethernet card and is booting from a "Tecnobytes ClassicIDE" - I can tell that it's booting every time (even when the screen is black) based on the LED activity on the Tecnobytes card - it really does seem to be just a video issue, not an overall-system issue, if that makes sense. The flickering / black screen behavior is the same even after I remove all the upgrades.

Here's a short YouTube video showing what it's doing - please note that even with the challenges of filming a CRT with an iPhone, the screen actually looks brighter and more readable in this video than it does in person.

Based on the above, what direction should I be investigating? Tomorrow I'll pull a TV from storage so I can test the Composite video output - I'm curious if that's working fine or not. The IIgs's capacitors (both logic board and PSU) are still original - would failing caps account for this behavior? I've inspected the board and don't see any sign of leaking capacitors and the original battery was removed ~20 years ago when I first got the machine, so no damage there (thankfully!).

I'm really hoping I can exhibit this machine alongside some other classic Apple (and related) systems at our upcoming Retro Roadshow events in March - any tips would be really appreciated!

 

[Callan]

Every iigs I've looked at has had bad caps in the power supply. I would definetly check them. You might not see anything, but once you desolder one you'll smell it! Try one of the bigger filter caps by the power connector going to the motherboard.

 

[bibilit]

Yes, was thinking the same thing, poser supply issue first.

 

[Huxley]

That's totally fair and valid feedback, thanks @Callan & @bibilit. I gave the PSU a closer inspection and noted a faint but distinctly fishy smell, which I suspect points to leaking caps and/or a burnt RIFA. I've ordered a new PSU from ReactiveMicro - excited to get it installed and see if the situation improves!

Huxley

 

[Arbee]

The IIgs RGB monitors are prone to cold solder joints on the flyback transformer. I've had to reflow mine every so often to keep it from doing that flickery thing. If you give the monitor a firm thump and it changes the flickering, even briefly, that's probably what's happening.

 

[nathall]

Side note, where’d you get that DOOM desktop picture?

 

[Huxley]

Side note, where’d you get that DOOM desktop picture?

I found it in a bundle of IIgs images / apps that I migrated to my CF card a while back. If / when I get the machine running again I'm happy to export and share!

 

[cruff]

Burnt RIFA caps smell like burnt paper.

Have you checked for bad solder joints?

 

[Huxley]

Hi all,

I’m back with a few quick updates:

• I successfully recapped the IIGS motherboard yesterday. It was a challenging project for me, as some of the capacitors are tiny and packed pretty close together on the board, and the old solder was super stubborn and frequently didn’t want to come out smoothly
• I’ve also installed a brand new IIGS Power Supply from ReactiveMicro
• Sadly, I’m still unable to get a reliable image on the IIGS RGB monitor - it worked for ~15 minutes before it started flickering, faded out, and never came back again
• Interestingly, the IIGS‘s Composite video seems to work fine going into my Commodore 1084 display

Any suggestions on where I should be looking next?

 

[finkmac]

sounds like your monitor needs repair

 

[Callan]

if it's working fine with the composite monitor I'd agree with Finkmac. Arbee previously mentioned the monitor is prone to cold solder joints on the flyback. Since you've had it capped I'd check there first. You might also want to check your adjustment pots (brightness). They can cause what your describing too. You can use contact cleaner or they make a de-oxit for potentiometers (faders fs). Bar that, you can replace them. I'd use a meter to check if the pots are tracking correctly to.check them first. Also check the neckboard for any cold solder joints. If your heater had an intermittent connect it would cause it to do the same thing.

 

[Huxley]

As of now, the RGB monitor is probably the only component that I'm reasonably confident is working correctly, just based on the recent repair and calibration it's received.

I noticed that the image on the RGB display flickered back to life for a moment when I pressed down on the IIGS motherboard along the back where the slots are. Based on this I suspected that maybe there was a broken solder joint, so I've just carefully reflowed the solder on the RGB connector pins and all the other through-hole components in that area. Unfortunately, I'm still where I started: no RGB output at all, even while Composite works fine.

I'm feeling pretty sad and discouraged here, and I'm pretty much at the limit of what my current skills and knowledge allow me to accomplish. Anyone know of a good / trustworthy tech on the West Coast who I might be able to send this board to for a more expert-level assessment?

Huxley