Classic II Analog Boards were made to ruin lives

[svenvendetta]

Ok, since I know you could make a coffee table book with posts about the Classic analog boards here's my story so I can share some common misery:

I had both boards on a Classic II recapped by an expert and it was doing well for about 8 months then one day on startup: no chime, just clicking noises from the speaker. My best guess is that the analog board is likely shorting out somewhere with voltages being about half of what they need to be when metering pins for 5 and 12v from the logic board. The clicks go on a cycle with the fan doing a quarter spin every few seconds as it tries in vain to start. Strangely on 2 random occasions it has booted normal with the correct voltages but this is out of many reboots and connection reseats, poking, prodding, etc... Can't imagine the logic board is the culprit but not sure where to even look.

I have deoxit'd the voltage pot and cleaned off the board with iso alcohol. Same thing. Not expecting answers here just sharing the pain but if you got any ideas I am all ears

 

[CC_333]

I don't know lots about Classic II analog boards (aside from how unreliable they are and what a pain they are to fix, of course), but I have read that the optocoupler/optoisolator, which is part of the voltage regulation circuitry, tends to fail, and I think it can cause symptoms similar to what you describe (low and unstable voltages leading to a no-boot condition, even after a full recap) when it does.

c

 

[dochilli]

There are a lot of parts on classic AB that can be defect. Most often: DP3 and DP4 (1N4148), TDA4605, CNY17G, IRFBC40.

 

[joshc]

There is a reason I gave up on Classic/Classic IIs, and there is also a reason I wrote a thread about my hate for the analog board in these.

https://68kmla.org/bb/index.php?threads/the-classic-analog-board-the-most-frustrating-thing-to-work-on.38560/

The biggest reason they are unreliable is that they were cheaply made, both in terms of parts used and the design. It is a cost cut version of the Plus/SE analog boards. They went a step in the right direction with the SE (separating the CRT circuitry from the power supply) and then went backwards with the Classic... a lot.

But yeah, the above two posts are correct, there are a number of components that fail on these, and sometimes most of them need replacing before you get a working board again.

Best of luck with it, I share your pain...

 

[blindowl]

Ok, since I know you could make a coffee table book with posts about the Classic analog boards here's my story so I can share some common misery:

I had both boards on a Classic II recapped by an expert and it was doing well for about 8 months then one day on startup: no chime, just clicking noises from the speaker. My best guess is that the analog board is likely shorting out somewhere with voltages being about half of what they need to be when metering pins for 5 and 12v from the logic board. The clicks go on a cycle with the fan doing a quarter spin every few seconds as it tries in vain to start. Strangely on 2 random occasions it has booted normal with the correct voltages but this is out of many reboots and connection reseats, poking, prodding, etc... Can't imagine the logic board is the culprit but not sure where to even look.

I have deoxit'd the voltage pot and cleaned off the board with iso alcohol. Same thing. Not expecting answers here just sharing the pain but if you got any ideas I am all ears

My Classic II had the same issue just recently. After I did some cleaning and re-soldering of th Egret chip on the LB it suddenly came to life again.

 

[Cam]

Do any of the AB not cause misery?
The ones in my color classics were a huge pain to make work.
My SE machine got all new caps and refused to work, until I left it for a few days; then it worked (many bad words were used).

 

[imactheknife]

lol, yeah I am not a fan. I have recapped 4 classic analog boards, one works perfectly, other one is good, two are not working well. I recapped a color classic works perfectly now, but was funny at first. I think I made the mistake of using blue scsi (actually forgot) instead of actual hard drive on first boot after recap to help with the load on it. Second color classic didn't work after recap. All my power supplies work perfectly and I recapped my commodore 1701 monitor and it works 100%. Some boards definitely are a pain...

 

[Byrd]

I'd like to be in this club, too.

Classic II analogue board with DP3 and DP4 (1N4148), TDA4605, CNY17G, IRFBC40 (as mentioned) replaced; all caps replaced, outputting rock solid voltages, replaced harnesses, two known working Classic II motherboards chime, boot but do not output video. Heater on CRT neck on.

Given up for now. I suspect next up is resistor removal and checking, or to source another AB but I've already picked up two.

JB

 

[imactheknife]

It is so satisfying when the board and analog live in harmony after recap. I actually love using this thing..the classic a little slow.. classic ii is quite nice

 

[joshc]

Classic is more bearable on 6.0.8L and Classic II on 7.1.

 

[joshc]

What I would like to see, and it's definitely doable, just not easy, is a recreated video/CRT board for these, with the power supply separated into its own enclosure. I think someone on the forum, cannot remember their name, tinkered a lot with a Classic AB to get it running a flat screen and they separated the video/power parts when they were doing that tinkering.

 

[svenvendetta]

Thanks to all for sharing stories and insights, glad I am not the only one . I absolutely know there is a way to get this thing back going again but I think it's going to go in the "deal with it later" pile for now as the painstaking task of component replacement and the likely no difference outcomes will drive me even more crazy. Off the bench it goes so I don't look at it and get reminded and start obsessing again. A troubleshooting guide for the Classic AB would likely be a valuable resource for the inevitable folks who will find themselves in the same spot in the future.