Hunting short

[diskosteppas]

Hi all Ive got my drum machine open and it with it not powering up, I opened it to check voltages.

Power board connected to mainboard, Checking 7905 it gives out of spec reading.

Disconnecting the psu board from mainboard the 7905 returns to spec.

Checking mainboard, some IC's are hot. Caps seem ok. No other obvious damage.
I removed the  3 hot IC's and the 7905 is within spec again.

Is it safe to assume one or all of these parts are at fault please?

[Manul]

Is it safe to assume one or all of these parts are at fault please?

Everything is a guess until something is proved. Something connected to the output of these ICs could be shorted, so the ICs get hot. I would say your guess is a good guess, but it is not a safe assumption. Also it is a bit suspicious, that 3 ICs got damaged at once. It is possible, but not super likely. So you may buy them, replace and hope, or you may spend some more time and collect more information.

I don't know what kind of chips you removed, but your options might be checking supply pins of IC with multimeter (burned ICs sometimes have them shorted), try to power them outside the circuit. Get datasheet, see what IC does, trace and check inputs/outputs on the board. Many options.

[DavidAlfa]

I'd lift the 7905 output pin and put the amp meter in between.
Probably at least one IC is overloading the regulator.
Knowing the regulator has a limit of ~1.5A, note down the the readings without these ICs.
Then put back one IC at a time. If any causes a huge current flow, you found the culprit.
If after soldering all back the current isn't too big, then you could blame the regulator.

[diskosteppas]

I did not think to test current draw per IC at a time. I'm going in. Thanks for the tip!