exxos's Atari, Amiga & retro forum

What I’m wondering is if there is a common component that was fried that affects the entire motherboard. If so, what is it.

Glorfindeal wrote: 25 Jun 2024 11:13 What I’m wondering is if there is a common component that was fried that affects the entire motherboard. If so, what is it.

Not sure what I can suggest at this point other than going over the mainboard and looking for anything that is obviously fried, but if you have earth and it was in use, it's likely that shorting it out simply shorted 110v to earth.

When you shorted it out, where you touching any other part of the mainboard when you touched 110v? If so look there, but otherwise you're looking for a decent retro repair shop that knows Falcons.

The fan uses the 12v rail and is not shorted, hence the running fan.

Could you check if the 5v rails are shorted? If these measure 0 Ohm or slightly more, then there's a short. I once had a Falcon from a client with a shorted ceramic capacitor on the back of the board, creating a short on the 5v rail. Once found and replaced, the board was working again.

You could try Mutant Caterpillar if you are in the UK. Like someone already wrote, I wouldn't trust your Falcon with someone who hasn't worked on Falcons before.

When checking the 5v rail do I measure from the 5v pad on the psu and a ground point?

No, disconnect the PSU from the mainboard and measure the connector on the mainboard. The pinout of the connector:

1. +12v (Blue)
2. Gnd (Black)
3. Gnd
4. Gnd
5. Gnd
6. +5v (Red)
7. +5v
8. +5v

Measure the 5v rails with one of the ground pins on the same connector. Set your multimeter to Ohms and if it reads 0 Ohm or a bit more, you have a short.

I tested all 3 +5v pins and are 3 read 0 ohms. :|

Glorfindeal wrote: 26 Jun 2024 13:05 I tested all 3 +5v pins and are 3 read 0 ohms. :|

Ok, the 5v rails are shorted to ground and I guess there might be a faulty decoupling capacitor somewhere on the (back of the) mainboard.

Given you're from the UK, you could contact Ian Gledhill from Mutant Caterpillar and ask him to have a look at it. I would know anyone else who could have a look.

No, I’m in the US. I did send an email to Mutant Caterpillar though. Can’t find anyone in the states to look at it. It would be cheaper to send it to the UK than to buy a replacement motherboard.


Ken

There must be lots of electronics repair companies in US capable of PCB diagnostics for power-shorts.

If there are, they are hiding. Most of them only do vintage game console repair. Of the 2 that I did find, I didn’t want to work on it and the other never returned my emails.