Mystic upgrade problems

[Ttpilot]

Hi all. I recently picked up a Color Classic in good shape, other than a dead hard drive. It did boot up to the no-operating system prompt. I also picked up an LC575 logic board which looked to be in good shape, plus a couple of 68040 processors from eBay. I carried out the 640x480 mods to the analog board (Rev C). Reassembled, the system has the analog board mods, LC575 logic board and a full 68040 processor.

When I switched on the power I heard a hum from the analog board or monitor. I noticed the neck of the crt monitor didn’t glow. When I pushed the start button on the keyboard I got nothing—no sound, no picture.

I‘ll try some variations next, e.g. swap the 68LC040 back in, etc. would it be safe to try the Color Classic logic board after the analog board mods?

I’m looking for suggestions as to how to go about finding a solution

BTW the LC575 logic board was described as:

Recapped Macintosh LC 575 logic board. Can be used to turn a Color Classic into a “Mystic” or can be used in the larger all-in-one LC/Performa 520-578 chassis.
Recapping was done with professional equipment and components. In this case, tantalum capacitors were used.
Listing includes 132MB RAM (maximum known config - hard to find working SIMMs) and 2x 512kb VRAM as pictured AND the rear motherboard back plate for a Color Classic - 3D printed in off white or tan ABS (can be painted).

Analog board mods shown. I followed the instructions at Powercc.org Option 1

 

[Ttpilot]

Okay, I popped the original 68LC040 back in and the system booted. I have one more 68040 I might try later. I did some screen adjustments, and this is the best I got



I’ll keep working on it. Next I need to get the OS working

 

[Byrd]

It's usually the edge connector that is dirty/motherboard isn't properly slid in that causes no boot, might not be the CPU which is pretty hard to fry.

 

[MrFahrenheit]

Just be aware that many 68040 sold on eBay are fakes (remarked and not what they are claimed to be) unless sold by a very reputable seller or an individual collector in the”western world”.

I’ve purchased said fakes for the purposes of determining what they are.

One of the best and most legitimate suppliers of CPU chips is Eric Woo on eBay.

 

[Ttpilot]

Just be aware that many 68040 sold on eBay are fakes (remarked and not what they are claimed to be) unless sold by a very reputable seller or an individual collector in the”western world”.

I’ve purchased said fakes for the purposes of determining what they are.

One of the best and most legitimate suppliers of CPU chips is Eric Woo on eBay.

Understood. I purchased 2 of them knowing that was a possibility. I still have one I haven’t tried (which I’ll remedy soon). At the moment I’m getting software loaded, and I need to figure out why the screen is skewed. From what I’ve seen that might be due to a cap on the analog board

This is the pair of chips I bought, btw



I was a bit suspicious because the arrow mark in the corner looks very faint

 

[MrFahrenheit]

Understood. I purchased 2 of them knowing that was a possibility. I still have one I haven’t tried (which I’ll remedy soon). At the moment I’m getting software loaded, and I need to figure out why the screen is skewed. From what I’ve seen that might be due to a cap on the analog board

This is the pair of chips I bought, btw

View attachment 76974View attachment 76975

I was a bit suspicious because the arrow mark in the corner looks very faint

Those look legitimate from a glance.

 

[Ttpilot]

I put in the other 68040 processor and it worked. Also, fiddling with the monitor adjustments some more got it straightened out. Now comes all the fiddly work of installing extra software…