blown fuses Kustom KBA16

[2manygits]

Hi I'm new here and in need of some help. I have a small Kustom Bass amp, KBA16, that worked fine but was unused for about 2 months, when I plugged it in it blew the fuse ( the switch was on at that time, I thought it was off). I replaced the fuse and it blew again when powered up. Is there anyplace I can get a diagram of the circuit? I haven't isolated the transformer or the rectifier yet, but if they are not the problem I am in a little too deep without the diagram.
Thanks to anyone who can help.

[Enzo]

It couldn't hurt to CALL Kustom and ask if they can provide the drawing.

otherwise, this is a small basic amplifier. The circuit is not complex. You don't need to isolate the rectifiers, just check them in place for shorts. If they measure shorted, then isolate and remeasure to be sure. But if a diode in circuit measures not shorted, there is nothing any circuit can do to make a shorted part appear not so. You can disconnect the transformer secondary - it should be simple to identify - and if the fuse still blows, likely the tranny has failed. but while it does happen, transformer failures are the lowest thing on the likelihood list.

But when amps like this blow fuses, by far the most likely thing wrong is a shorted output device. many small amps like this use a power amp IC. The owner manual for this calls the power amp "transistor" so there may be a pair of them on the heatsink. Check them for shorted.

[2manygits]

Thanks Enzo, I haven't called Kustom but I did email them several days ago. I'll check out what I can and if I don't find anything, I'll give Kustom a call. I know it's not a big amp, but I like it. I have 2 other bass amps but they are too big for home practice so I would like to fix it.

[Jazz P Bass]

At 16 watts of output, I would guess that Kustom used a TDA2050 output IC.

Check pin 3 & 5 for a short.
(Pins 1, 3 & 5 sit forward, 2 & 4 are to the rear.)

TDA2050 pinout.pdf