MK1 Y-Unit Dead

zenomorp

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Donor 2015
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Ok. I had a guy ship me his MK1 PCB because he had no sound (no power cable or volume pot) so I could solder him up a cable and volume pot. When I got home from work to find the box in front of my door, I picked it up and I could hear the sound card rattling around inside. I thought "Oh, great, this should be fun." I opened it up and neither the main board or the sound board were wrapped in anything. Just laid on top of some bubble wrap. Now, low and behold, the main board doesn't power up. There are 2 LEDs that are supposed to illuminate. The top one illuminates to show that the board is powered on and the bottom one is supposed to flicker to show that the board has activity. It does nothing. Only the upper one is on and constant, indicating no activity. Also no picture at all. I emailed him and told him what was going on and told him I'd take a look at it and see if I couldn't fix it. So, I am here asking if anyone has come across this type of malady before or know how to fix it. I checked the solder side of the board and no socket feet are touching each other. Also removed and reseated all the chips that are capable of being reseated. Thanks for your time. - Mike.
 
Look again. There has to be something gouged or otherwise damaged. pins on the board bent over and touching... resistor packs broken... something has to be broken for it to just die.

Is the CPU socket OK? Did it crack?

IIRC, there are no surface mount components besides the CPU...
 
If you have an EPROM programmer then check to see if you have a bad program ROM.

Were there any extra pieces in the bottom of the box?

If it were me, I'd start this way:

Check EPROMs - Bent pins? Backwards? Do they have the right checksums?
Look for missing parts.
Check the clock crystal or crystal oscillator for damage.

Check for broken passive components (resistors and caps) and active components (transistors)

RJ
 
If you have an EPROM programmer then check to see if you have a bad program ROM.

Were there any extra pieces in the bottom of the box?

If it were me, I'd start this way:

Check EPROMs - Bent pins? Backwards? Do they have the right checksums?
Look for missing parts.
Check the clock crystal or crystal oscillator for damage.

Check for broken passive components (resistors and caps) and active components (transistors)

RJ


Removed and reseated all the roms. No good. No way to tell if they are good as I have no burner/programmer. I did find two traces that had been scratched open. I repaired them, but still no change. Visually, there is nothing wrong that I can see. Here is what's going on right now...


http://www.youtube.com/watch?v=awt4tS1k0og
 
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