Cannot see anything physically wrong with either C25 or R34 so will get and fit replacements to test.

I have checked the HP socket- seems ok, no dry joints, good continuity. But I was checking it with my HP adaptor (small jack to large) and I remembered that this adaptor is a bit suspect. Could it be that a intermittent headphone connection could cause the amp to blow (I was using this adaptor on both occasions)?

There was no inslating mica on the chip when I removed it so I didn't put any in on the replacement. Is that going to cause a problem? ...I meant to say about that the expensive thermal grease would stop it overheating on its own sorry about confusion, but didn't consider electrical conductivity... however the second time I used standard thermal grease for the replacement and it still blew (after only a couple of minutes). Interestingly both times it blew only after switching off and back on.

About the "maybe the guy who sold it to me knew something" thing... I was just ranting in anger... you're right Enzo noone could know when something is going to fail... unless of course it had failed before and he hadn't mentioned this concern to me.

Hi not sure where to look on the circuit diagram (link above). Perhaps you could suggest appropriate capacitors to check on the diagram. Note that it is possible that it is a problem with headphone output as it happened after I was listening on the headphones. I can't be sure about this but it was ok for an hour without the phones then it blew after I used them and the second replacement chip also blew almost immediately and I was using headphones from the start then because I thought it might be the loud pop I get with the amp when I switch it off. Thanks.

I replaced the chip and it worked... for a while. But after about an hour or so playing I switched it off and when I switched it back to test it the hum was back. I didnt wait for it to burn. The TDA 2050 was held with a clip onto the heatsink. I replaced the thermal grease with expensive silver thermal compound. So I shouldn't think it overheated. Anyone able to shine any light on possible problems or other components that may be at fault. Thanks.

You are right it is a TDA2050 I can just make it out on the chip. Don't think I can use the LM1875 as direct replacement without modifying the board so will have to buy another chip. Thanks for the info and the schematic. After further reading I think the problem might have been caused by plugging my iPod into the CD-In port as others have said the TDA2050 is a poor quality chip that cannot take the input and is easily blown. Will let you know if fitting resolves problem. Thanks.

I have looked at the chip and it is fried - cracked and burned. The rest of the circuit looks in good shape visually. Unfortuntely I cannot find a schematic for this board. I have searched but to no avail. Maybe someone knows of its existance? Anyhow I have ordered repacement LM1875 and will try that first then. BTW I wonder what caused it. This amp was second hand and has always made the biggest pop when switching on and off. I have only had it for less than 3 weeks so maybe the guy who sold it knew something was up...

Hi wondered if anyone could give me some advice about the possibility of fixing my marshall MG15CDR which blew up this morning. When I switched it on it emitted a constant loud low hum. I left it on for about 1 minute while I fiddled with the controls and then noticed smoke coming from the back of the unit. I switched off and removed the control chassis and looking at the board I can see a burn around the pins of the op-amp. It has burned the board a little but the tracks are ok. I believe this is a LM1875 based amp. Is it likely that I can just replace this chip to repair or is it likely something else is wrong? Thanks.