More of the usual. Where to?

[mst3k]

Greetings,
I'm trying to revive my Mac Classic.
When I boot, there is no chime and I get the classic checkerboard with additional wobble (see video).
When I boot with the memory card installed, I get no chime and the classic horizontal lines with wobble (see video).

The logic board and analog board have both been recapped.
The recap made NO difference to what you see in the video. It behaves exactly the same.

Where to...?

Thanks in advance for your help!

 

[Bolle]

It looks like you have corrosion inside the power connector on the logicboard.
Cap juice can make its way up there from the caps that are sitting right next to it.

Can you confirm if there is indeed actually corrosion on the pins? If there is the cable will likely be corroded as well.
Result is that the logicboard doesn't get enough power and might be stuck in reset. If the pins for the video signal are corroded too that might explain your wobble as well.

 

[bibilit]

I agree with Bolle, what are the voltages ? probably the 5 volt rail is too weak.

 

[mst3k]

Thanks for the reply.
There is no corrosion on the logic board connection, only residue from the ridiculous amount of corrosion on the analog board connector.
I've been working on cleaning out the analog board connector, but did you say that the corrosion can crawl back inside the wire?
Does that mean I need to install a new/replacement analog board connector and harness?

pin 6: 3.84v
pin 8: 9.88v
pin 5: -10.55v

Obviously, I'm way under spec for voltage.

 

[mst3k]

and the answer is....?

Optocoupler. Optocoupler. Optocoupler.
Just installed a new optocoupler 'et voila!'
12.05v, 5.02v, -12.07

New caps. Reflow the cable connectors.

Bong and boot. All's well that ends well!

Thanks for the help and the excellent data source from the 100's of posts to this website that got this machine working!

Optocoupler!

 

[s_pupp]

The optocoupler for my Classic was the CNY17G-3. If you order from Mouser, check the part number on the part you receive - I was sent a CNY17-3 which didn’t fit.