Dead PET4032

[Adrian Graham]

Hi folks,

Some storage reorganisation last week uncovered a PET4032 I'd forgotten I
had. Spotless internally (I remembered why later) and glass fuse intact so
I attempted powerup. Nothing. No screen and no chirrup.

Google + schematics time. I've checked AC voltage at the iron lump and all
major chips + DRAM are getting the right voltages. The processor is
generating a clock signal at PHI2 (~2.7V), I've checked continuity of all
address and data lines for ROMs/processor/VIA/PIA. I can't check the
contents of the Kernal ROM since it's not socketed and my track record of
successfully removing big chips whole isn't good.

One chip that does get hot is the Character Generator at UA3 which I was
going to swap with the one in my other 4032, but that doesn't power up
either. Presumably I can borrow one from a 3032 or 8096?

A lot of the repair pages use a piggyback 6502/ROM/RAM add-in called a
PETvet but all I have is a DMM, logic tester and other working PETs as
sources of chips I can borrow.

Are there any more steps I can try before checking ROM contents becomes
necessary?

Cheers.

-- 
adrian/witchy
Owner of Binary Dinosaurs, the UK's biggest home computer collection?
www.binarydinosaurs.co.uk