Blown resistor, cant figure out what it was.

[budm]

Re: Blown resistor, cant figure out what it was.

Test diode like you do a transistor so only goes one way? Not tested a diode before but have done a transistor

Can I do in circuit?

The IC did have some blackness on the pins but that probably came off the resistor.

ill do that now

You can test that Diode in circuit just using Diode mode on your meter.
The Cathode side of the Diode feeds the 680 Ohms to GND, it also feeds 8K2 Ohms resistor (another end of the resistor feed pin 21 of the IC and the peak charged capacitor.

[mikay786]

Re: Blown resistor, cant figure out what it was.

diode looks ok reads 0.548v, only one way

[budm]

Re: Blown resistor, cant figure out what it was.

diode looks ok reads 0.548v, only one way

That is fine.

[mikay786]

Re: Blown resistor, cant figure out what it was.

http://www.maplin.co.uk/p/metal-film...m-resistor-m1k

is that ok as a replacement resister?

[budm]

Re: Blown resistor, cant figure out what it was.

It is just a generic carbon film resistor 1K 5% 1/4 W. No need for 0.6w 1% resistor.

[mikay786]

Re: Blown resistor, cant figure out what it was.

I don't know the difference between the two. Maplin's is local so can just go pick that up today if it will do.

[budm]

Re: Blown resistor, cant figure out what it was.

That will work.

[mikay786]

Re: Blown resistor, cant figure out what it was.

Nice one budm, looks like no other damage was caused and is working as it was. I would probably have been still staring at the wrong schematic!

Got rid of the scratchyness by cleaning pot but still got the static at full volume when speakers are idle (no music playing) I'm thinking this is normal now as cant be heard when music is playing only when paused and at full volume. The left channel does this too but at about 50% less.

[SteveNielsen]

Re: Blown resistor, cant figure out what it was.

I'd clean switches and check the caps. I wouldn't considering it normal, it may be tolerable, but it could be better. The 40mV DC offset on the RT spkr output may be tolerable but it's not quite right. I suspect a leaky cap, not physically leaking goo but leaking DC current through it that it's supposed to block.

[mikay786]

Re: Blown resistor, cant figure out what it was.

Cleaned all switches and pots so I don't think they are the cause. You are probably right about a leaky cap but there are 100s of them and its probably not worth the cost / effort to change them all.

Might also be because I'm running with one fuse missing at moment, have misplaced the fuse cap.

[SteveNielsen]

Re: Blown resistor, cant figure out what it was.

It'd probably be in the final output amp. Have you been able to get the right schematic yet?

[lookimback]

Re: Blown resistor, cant figure out what it was.

I learned the hard way that you should always take good clear pictures before you start taking things apart. I can't tell you how many hours I spent looking for pictures on the internet when I forgot what orientation a component was in, or something blew up, or even just crumbled when trying to remove it. As a general rule, I clean up any part I'm going to remove and write down the numbers which are on it, for ICs I permanently mark the location of pin 1 with a light scratch if it isn't already marked on the board, for diodes mark the cathode location the same way, then I take pictures.