I was wondering if anyone had a electronic manual or Doc on testing motherboards (ICUs, Caps, resistors and such) and what the readouts should be on a multimeter. Does anyone have any ideas on what I can check for?I really want to get her up and running (been a few years). Also is there a way to test the PSU and what should the readings be on the pins in the plugin to the MB?
The board only needs +5V (+/- 10%) to boot, which is from the fat yellow wire on the main board power conector. Probably not power supply related given your clues so far.
The
schematics are easily available.
In terms of fault finding, you need to start with the basics such as are all reset lines inactive (high/5V), are all clocks valid, valid p-p levels on address and data bus lines. Check the overlay line from U350 is being set after power on, indicating initial ROM data is being read and CIAs can be written to.
Common faults are battery corrosion around U177, U891, etc. If these parts look corroded, remove them using a SMD rework station and see if the system boots. It doesn't need these parts fitted to boot, though of course you'll have no RTC or fast memory.
If you can't get anywhere, I can send you an estimate to repair.
http://amiga.serveftp.net
