Laney HCM30R Guitar Amp .....Faulty!

[shadowfax]

Laney HCM30R manual
https://www.electro-tech-online.com/custompdfs/2009/02/HCM30-R-B20Manual20-20200220-20Issue201.pdf
Service Manuals
https://www.electro-tech-online.com/custompdfs/2009/02/HCM30R.pdf
https://www.electro-tech-online.com/custompdfs/2009/02/HCM30R-CH.pdf

(HCM30R-CH.pdf looks to be the closest to my circuits, a later design)

Hi, I'm trying to repair my Laney HCM30R which was fine but now when you switch on makes a deep 'burrrring' noise until the power fuse goes. At first I thought it was just the fuse but I've nearly got through my pack of ten spares starting it. All I did was put in an effects pedal and switch on. There was no sound (no overdrive, main volume about 1 probably). I'd left in the 3.5mm headphone adapter, not the headphones as they where 2.5mm ones I'd unplugged them seperatly.
After a few seconds I noticed the light go out, before I notice the adapter.
Since then problems.

Could anyone give there opinion on the probable cause, I'd be suprised if some kind of power build up blew something as these amps seem pretty tough. It may have been a power surge, but then again I've used my little old Kustom 12w without problem?

I'd appreciate any help you think you can think of.

 

[Nigel Goodwin]

Usual cause of the 'loud buzzing' is failure of the output stage, in this case a TDA2050. Repeatedly putting fuses in and blowing them is likely to cause further damage as well, and isn't a good idea.

 

[shadowfax]

Haven't tried that often, Nigel had to get my bearings with what was up.

 

[shadowfax]

Just to update...... it was the TDA2050, which I swopped and it's working again. tada.
phew, hope it stays that way.