AES stuck in watchdog (fast click of death), garbage screen

[kazuo]

Back again with another AES in a bad way... this one was stuck in the click of death (fast clicking/popping), then I started messing with it.

I immediately found a bunch of corrosion around the LSPC2; I cleaned most of it and ran a few bodge wires, and I was able to buzz everything out (most of the bodges were lines going to the 68K data bus). From there, I socketed the BIOS and installed a Diagnostic BIOS, but continued to get the same watchdog error. I shorted DOGE (ha; pin 94) on the B1 to GND to disable the watchdog, and now I get alternating forms of colorful garbage:

Here's what else I can remember doing:

• Buzzed NEO B1 to the LSPC2 (PCK1/PCK2: Latch signals coming from LSPC2-A2) - checks out
• Buzzed pretty much everything between the LSPC2 and 68K data bus (D0~D15: 68k data bus) - checks out
• Buzzed the vias and lines I could see between the LSPC2 and the work (?) RAM (CXK58256 I think) - checks out

From reading around, work RAM seems like a possibility, as well as a bad 68K (oh no). I don't want to spend all day buzzing out every single thing on the board, so I'm curious if anyone has any ideas on where I might want to focus in on. I don't mind changing out the work RAM, but I'm hesitant to swap larger ICs since I don't have hot air or a desoldering gun at the moment. Eager to hear what others make of this.

Thanks!

 

[kazuo]

UPDATE: I buzzed out everything I found on this post (post #5 to be specific): LSPC2<->G0/D0<->43256; 68K<->E0<->HC259 (or thereabouts), as well as BIOS pin 20 to E0 pin 59. Everything checks out. I also buzzed out the BIOS to the 68K, seems like everything's continuous.