Help diagnosing a Color Classic Analog board

[jcm-1]

I have a CC Analog Board in for repair. It no workie.

Symptoms:

• Screen is BLAZING bright regardless of adjustments
• Retrace line is very visible
• No logic board chime

Things done:

• @Branchus standard recap for this board. Had no effect (although it needed it)
• Checked silicons at DL5 and QL1 and DP19 (all good)
• Reflowed all big solder joints

Things tried:

• Two different known working logic boards.
• Two different known working chassisesssessssesss.

Any thoughts? I don't know where to go from here.

 

[Vintage_H._Shack]

Just a shot in the dark, but with the audio equipment that you have on hand for producing video content, you might be able to compare the sound waves emitted from the "dead" CC and compare that to your healthy CC. This is just a blind shot in the dark hunch based on my kids' reaction to any CRT being powered on at my house. Also, if I power up a CRT TV or monitor that has that infamous high pitched noise going all over the scale, you could chase that rabbit down the hole. Perhaps this may ultimately lead to a bad flyback or cracks in the analog board in that location? I would try recording the audio as close to each machine as possible and compare the outputs, then go from there. At this point, you don't have much to lose from trying this. Just trying to help...

 

[jcm-1]

Just a shot in the dark, but with the audio equipment that you have on hand for producing video content, you might be able to compare the sound waves emitted from the "dead" CC and compare that to your healthy CC. This is just a blind shot in the dark hunch based on my kids' reaction to any CRT being powered on at my house. Also, if I power up a CRT TV or monitor that has that infamous high pitched noise going all over the scale, you could chase that rabbit down the hole. Perhaps this may ultimately lead to a bad flyback or cracks in the analog board in that location? I would try recording the audio as close to each machine as possible and compare the outputs, then go from there. At this point, you don't have much to lose from trying this. Just trying to help...

Thank you for the help. My recording equipment isn't as fancy as you think it is. In addition, I can't run this machine for more than a couple of seconds, as I'm afraid it's pushing crazy voltages and is going to fry something.

I have already checked the analog board with a magnifying glass and have reflowed all the heavy solder joints.

 

[techknight]

I have a CC Analog Board in for repair. It no workie.

Symptoms:

• Screen is BLAZING bright regardless of adjustments
• Retrace line is very visible
• No logic board chime

Things done:

• @Branchus standard recap for this board. Had no effect (although it needed it)
• Checked silicons at DL5 and QL1 and DP19 (all good)
• Reflowed all big solder joints

Things tried:

• Two different known working logic boards.
• Two different known working chassisesssessssesss.

Any thoughts? I don't know where to go from here.

Well first, adjust the G2 (screen) drive on the flyback and see if that brings it down to a reasonable brightness. If not, your missing the proper cathode voltages to keep the CRT from going into full saturation so theres likely a cause such as a bad solder joint, or open connection/resistor.

 

[Branchus]

Well first, adjust the G2 (screen) drive on the flyback and see if that brings it down to a reasonable brightness. If not, your missing the proper cathode voltages to keep the CRT from going into full saturation so theres likely a cause such as a bad solder joint, or open connection/resistor.

Welcome to Tinker Different, @techknight!

 

[jcm-1]

Well first, adjust the G2 (screen) drive on the flyback and see if that brings it down to a reasonable brightness. If not, your missing the proper cathode voltages to keep the CRT from going into full saturation so theres likely a cause such as a bad solder joint, or open connection/resistor.

This was exactly the problem: missing solder on a resistor. To be fair, I didn't do that: the owner did and I missed it three times.

Now the CRT has brightness flicker problems, but that's probably just bad caps under the cage (i.e. the ones that don't normally get replaced).

Thank you very much for your help.

 

[techknight]

This was exactly the problem: missing solder on a resistor. To be fair, I didn't do that: the owner did and I missed it three times.

Now the CRT has brightness flicker problems, but that's probably just bad caps under the cage (i.e. the ones that don't normally get replaced).

Thank you very much for your help.

Spray the potentiometers with Deoxit F5

 

[JDW]

Spray the potentiometers with Deoxit F5

That advice got me thinking today...
I have been using Deoxit "D5" for a while now with success on corroded (slightly green) cables/connectors on my compact Macs, but your mention of "F5" now has me curious. Not sure if you've tried either on the Brightness Knob of compact Macs like the SE/30, but I'm curious if either either would work just as well or if F5 would be better than D5 in that case. I guess it may have something to do with F5 offering more long term lubrication of moving parts than D5, which means F5 would probably be better in the long term.

Amazon Japan sells both F5 and D5, and I purchased my current spray can of D5 from there for US$16 equivalent, but the F5 spray costs a whopping $21 for some reason.

 

[jcm-1]

While waiting for Deoxit to arrive, I removed the analog board again, reflowed every joint I touched, and even a few I didn't. This made no difference.

So, I took a black nylon stick and started poking stuff (non-conductive, ya know, for safety and stuff). Lo and behold: I poked one of the 5600uF caps at the front right of the board and now the video is just fine.

WTF?

I reflowed that joint at least three times, and cleared/cleaned it at least once.

The No-Chime was due to me not having the speaker plugged in, like an idiot.

 

[JDW]

I poked one of the 5600uF caps at the front right of the board and now the video is just fine.

Which implies if you poke it again, the video should return to its problem state, correct?

 

[Mac84]

...So, I took a black nylon stick and started poking stuff (non-conductive, ya know, for safety and stuff). Lo and behold: I poked one of the 5600uF caps at the front right of the board and now the video is just fine.

WTF?

I reflowed that joint at least three times, and cleared/cleaned it at least once.

The No-Chime was due to me not having the speaker plugged in, like an idiot.

Don't question it! Cover the whole thing in resin and don't breathe on it!

 

[jcm-1]

Which implies if you poke it again, the video should return to its problem state, correct?

One would think. But now it doesn't. It's just.... fine.

 

[jcm-1]

Update again: it's the board edge connector. Machine started flaking again. I got angry, so I removed the a-board, reflowed EVERYTHING, and reinstalled. Now, the screen doesn't flicker, but it's blue. If I "jiggle" the a-board, the screen flickers, gets color back, etc.

Now, I get to disassemble this thing for like the 100th time and clean/adjust the board edge connector. Nice.

 

[JDW]

... clean/adjust the board edge connector. Nice.

DeoxIT D5 on the board edge connector?

 

[jcm-1]

DeoxIT D5 on the board edge connector?

Yeah. Waiting on it to arrive.

 

[Mu0n]

Do you have any more updates on this @jcm-1 ? I'm thinking my problems with my CCII might be board edge connector related. Here's my recent thread about it:

https://tinkerdifferent.com/threads/mu0ns-color-classic-thread.1252/post-9567

 

[jcm-1]

Do you have any more updates on this @jcm-1 ? I'm thinking my problems with my CCII might be board edge connector related. Here's my recent thread about it:

https://tinkerdifferent.com/threads/mu0ns-color-classic-thread.1252/post-9567

Apologies on lack of updates. ADHD. I forget things.

The problems with this a-board were:
A) recap required
B) lots of loose solder joints
C) gunk in the edge connector
D) the female connector on the analog signal wire that goes from the front to the cage on the a-board needed to be cleaned.