Color Classic - no signs of life

[JC8080]

I recently picked up a Color Classic in unknown condition. The first thing I did was recap the logic board. I tried powering up (using a known-good ADB keyboard that works with soft power on my IIsi), and nothing. No beep, no fan, no hard drive spinning up. Just an extremely quiet whine that starts about a second after I turn the hard power on. Next, I recapped the analog board (all the caps with a Console 5 kit). Same result when I tried to power the machine on. I removed, cleaned, and re-installed both the CUDA and sound chip, still no change in behavior.

If I take the logic board out and turn the hard power on, the fan and hard drive spin up, and I can hear the CRT power up. No activity on the front LED light. Other posts have said you should hear a ticking noise when you start the machine without the logic board, and I do not have any ticking sound. Could that point towards something on the analog board? Or would having the hard drive connected put enough load on the PSU that the ticking would not happen?

If anyone has next-steps for troubleshooting I would be grateful for any help. A couple more points/questions below:

• Does the IIsi or LCIII have chips that would work in place of the CC CUDA or sound chip?
• The DL21 and DL22 diodes have both gotten hot in the past, the board is dark around them, which seems common. The diodes are in good physical shape. If the diodes are bad, could it cause these symptoms?
• When I beeped out the sound chip, pins 37 and 38 had continuity. I can't tell based on the Bomarc schematic if they should. I have tried with a 1/8 jack inserted, and either way I get continuity between 37 and 38. I am rather certain there is no solider bridge, unless it somehow happened way back where a dental pick slid between the pins wouldn't touch it. Schematic snip below.

Thanks!

 

[4seasonphoto]

Do you have a battery installed? I think some models won't start without one, IDK if CC is one of them.

 

[joshc]

Do you have a battery installed? I think some models won't start without one, IDK if CC is one of them.

All of these work without a battery.

reseat the analog board and logic boards after cleaning the connectors with contact cleaner. Colour classics suffer from bad connections just as much as bad capacitors. Make sure both are as tight as they can be.

You also need to ensure the logicboard ground loops are making good contact with the metal shield. Best to test with the rear case on to ensure the shield does not short anything on the logicboard.

 

[JC8080]

All of these work without a battery.

reseat the analog board and logic boards after cleaning the connectors with contact cleaner. Colour classics suffer from bad connections just as much as bad capacitors. Make sure both are as tight as they can be.

You also need to ensure the logicboard ground loops are making good contact with the metal shield. Best to test with the rear case on to ensure the shield does not short anything on the logicboard.

I sprayed the connectors for both the LB and AB with Deoxit and inserted/removed the boards multiple times to clean the contacts, no change in behavior. I also checked continuity on all legs of the CUDA chip and everything has continuity. I was definitely hoping I just had a broken trace.

I looked back at the pics I took before I cleaned the board, and the CUDA definitely has some corrosion on the legs. I'm definitely suspecting the CUDA at this point. Does anyone know a source for the 341S0417 CUDA or a compatible chip?

 

[chiptripper]

As I mentioned in your Trading Post post, worth checking the crystal. If the connection rots out between Y1 and the CUDA, you'd get no response from soft power. A trace runs from Y1 to a via, then to a ceramic load cap on the backside of the board. C6 very often rots out that trace or via entirely.

Of course, if there's bad corrosion on the CUDA legs, it could just as easily be the cause. But it's worth ruling out the above regardless because it will prevent soft power, new chip or not.

 

[JC8080]

As I mentioned in your Trading Post post, worth checking the crystal. If the connection rots out between Y1 and the CUDA, you'd get no response from soft power. A trace runs from Y1 to a via, then to a ceramic load cap on the backside of the board. C6 very often rots out that trace or via entirely.

Of course, if there's bad corrosion on the CUDA legs, it could just as easily be the cause. But it's worth ruling out the above regardless because it will prevent soft power, new chip or not.

Thank you, I will check later today and report back.

 

[JC8080]

I checked continuity from the CUDA to Y1 and unfortunately there were no breaks.

Does anyone know which CUDA chips are interchangeable? I found the list below in a post by Bolle from a couple years ago. It looks like only the color classic used 341S0417. If the others are interchangeable that would make sourcing one easier.

341S0060 Cuda (v2.40) Performa/Quadra 6xx, some PMac x200, PMac x400, some PMac x500, Pippin, Gossamer G3
341S0262 Cuda v3.0 some PMac x500, Bondi Blue iMac
341S0285 Cuda Lite ADB and PS/2 support - PMac 4400 & clones
341S0417 Cuda Color Classic
341S0788 Cuda (v2.37) PRAM, RTC, ADB

 

[chiptripper]

Dang. Shame it’s not just a bad trace.

Board is very similar to an LC II, which has a 341S0847, but I’ve not heard of a successful transplant, not that it can’t work, just no successful attempts.

Apparently the LC 550 used either the ‘0417 or the ‘0788, so the latter might work.

You can sometimes perform brain surgery on these chips… peel back the plastic casing with a dremel past the corrosion and then bodge, those leads extend a ways back. Then coat the repair in something protective and dielectric, clear enamel maybe.

 

[Arbee]

LC II uses Egret, not Cuda. They perform the same function but are not compatible.

 

[Arbee]

Also, in general using a newer Cuda than the machine came with should be OK, just don’t go backwards. (Cuda Lite and Cuda 3 are exceptions; Cuda 3 can work in older machines but I wouldn’t recommend it outside of an emergency).