Early 128k 512k analog board(s) repair

[avadondragon]

I recently came into possession of a 512k Mac. I was really excited because it has the RAM upgrade and a SCSI controller card soldered straight to the CPU!  But it also has a very fried analog board.  Specifically the transistor Q3 is burned to a crisp, CR1 and R14 got hot enough to discolor the PCB.  I'm attaching pictures.  This doesn't sound like any type of failure I've read about so I was wondering if anyone had any advice to give.

I also have an even earlier analog board that I think came out of a 128k or very early 512k Mac.  It looks like it has a burned up flyback transformer.  I know those are becoming very rare these days.  Maybe I could pull the flyback off the other board and see if it works?

I would like to repair one or both of these boards but I wanted to see if anyone had any input before I ordered the parts sitting in my DigiKey shopping cart.

 

[avadondragon]

Pics of the older analog board:

 

[Macdrone]

At this point trade all the good parts to the board with the least damage.  Its a great start.

 

[trag]

Dalbani on EBay or from their store, still has stock of the 157-0026 fly back, but their price is around $25 - $30 now. Still, if it's the only way to get a 'new' one... I think Artmix sells flashbacks as well. It looks like he paid to have a new production run made. I don't remember his pricing on them.

 

[Apache Thunder]

I'm seeing the entire analog board on eBay for slightly more then that. Better to just pick that up instead. There's only one listing for it though, so you better hurry.

The rest are way overpriced and you can find entire units for the prices they have for them.

 

[avadondragon]

I looked on eBay too and concluded that I could buy another analog board or even pick up an entire Mac Plus nearly as cheaply as I could repair these.  

The problem with that is ALL of these analog boards are almost 30 years old and starting to fail.  Even if I buy another it may fail in the next year or two.  I just feel like it is better to repair than replace if I can manage it.

I found a source for the 157-0042B at $25

The flyback from an SE is compatible right?

 

[CC_333]

All flybacks from the 128k throught the SE/30 are interchangeable. I'm not sure about the Classic/Classic II (I think so).

Later ones (like from an SE or SE/30) are better, because they are heavier duty than the early ones, and thus less prone to failure due to overheating.

c

 

[unity]

Maybe I need to pull and stockpile these. I have 3 SE/40 boards for parts and many, many other Plus/SE boards. But I agree, new would be best.

 

[avadondragon]

The reworks were a success!  My 512k is now fully operational!  I misplaced my 2nd flyback though so I only managed to finish one of the two analog boards.  Also managed to repair an old 1xx series PowerBook power brick at the same time.  Feeling super accomplished.  Next up: Centris 610 recap.

 

[uniserver]

nice bright crt picture   good job!

 

[bibilit]

Nice job, picture is a bit slanted, don't remember but think rotating the little magnets can solve this issue.