Color Classic noisy display

[ried]

I have a Color Classic that has a slightly noisy, high-pitched sound coming from the CRT. Strangely, the display is quiet when the original Color Classic logic board is installed, but the display emits the sound when the Color Classic II logic board is installed. I do not know why the display would behave differently. Changing the resolution or the number of colors (256 vs thousands) has no effect.

The sound is significantly louder when the case is on, too. If I leave the back case off, it's a little quieter.

Any ideas on how I might reduce the high-pitched whine coming from the display when the CCII logic board is in there? It's definitely the display / analog board, and the whine comes from the right side (when viewing the screen).

Thanks in advance.

 

[jajan547]

sounds like the speaker mine does the same with a color classic ii board, I have both the cc and ccii what's weird is I have no issues vise versa. Is the ccii recapped and is the analog board as well?

 

[ried]

Neither the CCII logic board or the analog board have been recapped (yet). The CRT only whines when the CCII logic board is installed.

I'll disconnect the speaker and see if that solves it.

 

[jajan547]

Yes let me know I’ll experiment on my end too both motherboards are recapped but my analog board isn’t on both the cc and ccii

 

[ried]

It was the speaker! Thank you. How do we solve that, aside from relying on external speakers? Is there a way to fix it?

 

[jajan547]

It was the speaker! Thank you. How do we solve that, aside from relying on external speakers? Is there a way to fix it?

probably just old, since yours is open can you take some ics of the speaker itself. I know there is a great stereo mod for these.

 

[ried]

Will grab some pics, sure. The speaker doesn't have any obvious damage or defect that can be seen.

This would seem to be an issue with the CCII logic board, though, correct? When the original CC logic board is installed, the speaker does not whine.

 

[jajan547]

Will grab some pics, sure. The speaker doesn't have any obvious damage or defect that can be seen.

This would seem to be an issue with the CCII logic board, though, correct? When the original CC logic board is installed, the speaker does not whine.

I'll look if I had schematics to compare to the color classic it'd be greta I have one just not the second revision. I'd imagine the sound is maybe slightly different but analog board should be the same.

 

[jajan547]

I'll look if I had schematics to compare to the color classic it'd be greta I have one just not the second revision. I'd imagine the sound is maybe slightly different but analog board should be the same.

I'll see if I can find the guide to that mod.

 

[jajan547]

Ah ha I found it. Link here.

 

[ried]

I don't think I'm up for a stereo mod. Here's what my speaker looks like, though, in case that provides any clues about why it buzzes with the CCII logic board.

 

[jajan547]

Stock speaker is 16Ohms

 

[ried]

Stock speaker is 16Ohms

Is yours different? Mine is stock, AFAIK.

 

[jajan547]

Is yours different? Mine is stock, AFAIK.

Mine is the same, any markings on yours?

 

[ried]

No markings. I'm pretty sure this is the stock speaker. So the issue is that the CCII logic board makes the stock CC speaker whine. Is there anything that can be done about that? Or do you have to disconnect it and use external speakers?

 

[jajan547]

No markings. I'm pretty sure this is the stock speaker. So the issue is that the CCII logic board makes the stock CC speaker whine. Is there anything that can be done about that? Or do you have to disconnect it and use external speakers?

Let me try it on mine rq

 

[jajan547]

No markings. I'm pretty sure this is the stock speaker. So the issue is that the CCII logic board makes the stock CC speaker whine. Is there anything that can be done about that? Or do you have to disconnect it and use external speakers?

Okay so Here's what I found CCII board in CC makes no pop noise this is after a recap. I did find that the LC575 board ("Mystic Mod") also had no weird noise. However, when I put in an LC520 motherboard or LC550 motherboard not recapped both made this noise.

 

[jajan547]

So I'm sure this is a capacitor issue on the logic board itself probably near the sound chip some cap goo is maybe interfering with it.

 

[joshc]

Recap the logic board before investigating anything else. Check voltages on the molex connector with the machine on, if 5v and 12v are weak/out of spec you need to recap the analog board too (recommended anyway even if you get good readings).

 

[ried]

Thanks guys. I think this will be my first and last 68k Mac. Good grief.