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

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

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!

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check PSU

If I understand correctly, you are using the original, unserviced PSU to power the machine, with several modern system upgrades.

PSU components, like electrolytic caps, don't only age by leaking electrolyte, they also dry up and become lossy. This sort of problem is more likely to manifest the more you load the machine with upgrades.

SpaceBoy's picture
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robespierre wrote:If I
robespierre wrote:

If I understand correctly, you are using the original, unserviced PSU to power the machine, with several modern system upgrades.

PSU components, like electrolytic caps, don't only age by leaking electrolyte, they also dry up and become lossy. This sort of problem is more likely to manifest the more you load the machine with upgrades.

That's totally fair and valid feedback, thank you. 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

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roly poly fish heads

A "fishy smell" betrays the presence of amine compounds, which are ingredients in electrolyte.

The Rifas don't have any smell until they burn; the smell of that is similar to burning hair.

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