Testing a Color Classic Analogue Board with no LB

[Tony359]

Hi all,

I am working on a CC in need of attention. Unfortunately it's been stored improperly.
The good news is that the LB is not too bad. Usual leaky caps which haven't caused too much damage. The battery is intact.

Now, there is capacitor leakage on the AB so I'm planning to fix that first. However, I'd love to test that power supply without the Logic Board.



I see two scenarios online

1. The CC will NOT power up the PSU without the logic board as the "power on" pin must be driven high.
2. The CC WILL power up the PSU with no LB but it needs a load (an HDD) to actually turn on or it will "click click click".

There is a video online (Adrian's) where he powers up a CC with no LB and the PSU starts as mentioned above. But I have friends swearing that a CC won't do anything without a LB and a keyboard connected.

So, is there a way I can test the AB by itself? Maybe shorting some pins on it so it's triggered to the "power on" state? I cannot find much on the LB schematics and AB schematics don't exist, sadly!

As before, to be transparent with the community, this is some paid work I have taken. I'm mentioning this as I don't mean to abuse of your help for personal profit.

Thank you!

 

[Tony359]

I'm going to answer my own post for future reference.

Yes, the AB will power up with no LB. Mine did not because it was bad.
If the "shutdown enable" pin is grounded, then it will NOT power up but with no modifications the AB will power up as soon as mains is fed to the board.

I haven't tested without but I think it needs a load (an HDD) to actually deliver some voltages.

Edit: I forgot: unless I am mistaken, the High Voltage will also come up with NO LOGIC BOARD so be careful