I have an old guitar amplifier with constant hum (even when the volume is at 0). I tried replacing the PS filter cap and output cap but nothing changed. Putting a cap across the speaker leads tamed the hum, so I'm guessing its the output transistors.

The two I need are

2SA966A
2SC2336

Both are TO-92L cases.

I'm having a hard time finding exact matches. Can anyone recommend a supplier of small (1 of each) quantities?

Thank you

 

2SA966A
2SC2336

You can get both datasheet from here

www.elportal.pl/pdf/k01/33_06.pdf

The matched NPN should be 2SC2236 not 2336..

Allen

 

Hum often comes from ground loops (or a re-wiring error were ground is swapped with signal wire on the output jack or the pick-up). Crossing wires on the input of the amp also causes the same hum.

 

Putting a cap across the speaker leads tamed the hum, so I'm guessing its the output transistors.

I don't think the diagnosis follows from the test. (But I must admit ignorance.) All the cap does is absorb high frequencies, including a portion of the hum. You want the hum to be gone before it gets to the power transistors.