Well it's time to learn how to fix something you screwed up

This was a working MPU. Decided to swap the 6264 U8 out to add a socket and NVRam. Usually I don't have problems but this one was tough and I know of a trace that pulled heading to the ASIC.

I grabbed my MM to check continuity from all pins on U8 back to ASIC. Repaired trace I pulled and found no continuity at a few more points. Probably pulled or damaged the pin hole connections. All pins now have continuity.

MPU is not booting at this time. I have another pin with the same MPU. Brought both out to my temporary test bench. Both hooked up to same power supply with my probe.

I will post vids of probing and hopefully someone has some suggestions haha.

Here is the crappy work I have done so far

IMG_6406 (resized).JPG

First boot test

Comparing U8 onleft board (not booting) to right board U8 I see I made a few errors reading schematic yesterday. I believe these are correct now for U8.

IMG_6413 (resized).JPG

Ok it's time for the probe

Due to limited and very amateur recording here is U21 left side

Here is the right side of chip

Here is the probe results for U8 left side

Ok right side of U8

Here is probe of U5 which is definitely showing different results between boards

Thanks. Yes the first pic with brown wire was incorrect. The second with the blue wire did not show continuity when compared to second working board. I did add the blue wire to match the working board.

You mention the blue could be removed...R93 is populated....if jumper is removed I have no continuity....Is this a possible sign of the problem?

U21
Pin 3 = Bad board low - Good board high
Pin 4 = high ---- Low
Pin 5 = high ---- Low
Pin 6 = low ---- High

U5

Pin 5 = low --- Show steady high low
Pin 8 = high --- Low
Pin 9 = Low ---- High
Pin 10 = high ---Flashes HL in sync with D20
Pin 11 =low ----Flashes HL in sync with D20
Pin 12 =low ---- High
Pin 13 =high ---- Low
Pin 14 =high --- High

These are the differences from probing

Confirming probe of U8 without 6264 ram.

Seems traces maybe ok now???

Well after more probe comparing I just noticed the ASIC is getting crazy hot. Set my hand on it and my palm of hand is still burning lol. I'm thinking this repair may not be happening lol

Well...This is the end the ASIC is dead. This will become a parts board

New board and ASIC on the way. Thanks for the help.

Ok update

Yes I have redone the jumpers with the wire wrap.

After confirming all my connections and using a spare board

ASIC Dead
68b09e Dead

Now only thing left is d3 and d4 are stuck together.

I only worked on two sockets which I removed again to eliminate the idea of pins touching and solder splash

Removed ASIC socket actually did this well lol. The original trace I screwed up went here.

Also removed all jumpers
Still D4 and D3 show continuity....