Well it's fixed I resoldered all the connections and put it back together and it's sounding perfect.

Really appreciate the help you guys and being patient with an idiot like me.

Cheers

Ok cheers didn't realise about the shorting resistor I only read about the 1meg grounding one so that makes sense I'll go over the solder and might just touch it up anyway.

So I found my problem.  My 1M grounding resistor (R1) is short circuited. It's a tiny little black one that I can't even read the writing on it let alone replace it.

Anyone know of an easier position for me to put another resistor as looking at it I very much doubt I can replace this.

I checked all the pot connection continuity and they are all sweet.

I think I may have found a problem with the input jack. I'll start browsing the prints you guys sent me to work it out.

Are input and output jacks wired the same way? I done some tests comparing the two and on both I get a circuit across each pair of connections with no jack in.

However when I plug the guitar in I get open circuit across the pairs on the output jack but on the input I get a circuit of 4k on one 300k on another and open circuit on the third. I also have a circuit between the top and bottom pairs on input jack only.

Sounds suss to me. Like I said I'll look the prints up and confirm but I figured you guys would probably be able to tell me straight up.

Thanks for helping,  I really appreciate it.

Rectifier and Poweramp all fixed now. I can listen to music from my phone through the mp3 input perfect but when I plugged a guitar in I get little or no sound.

Sometimes by playing around with the pots etc I can get it to work for a bit, however much quieter than it should be. Also it doesn't seem to be 1 consistent setting that makes it work.

I measured the pots and they are all 10K and adjustment is working.

Well the whole amp is mounted onto a sort of insulation tape so when I get a chance tomorrow. I'll replace the diodes and fix the washer. Then I'll probably be back to my original problem.

Quote from: g1 on March 13, 2015, 12:03:57 PM
  If it's not triple layer pcb, consider yourself lucky. 

Attached is the very extensive service manual for the III:

Haha it may well be. I failed to notice the 2 layers. The must be a short on the negative somewhere.

Probably my only concern when I pulled it apart was the way the power amp bolts to the chassis. And I think it's probably what's causing tho problem now I think of it.

The top tab is also connected to pin 3 of the amp which is the negative supply. However there it is booked to the chassis. I did notice the bolt has a plastic washer. Is this supposed to go inside the whole in the tab to insulate it from the chassis? In just using it as a regular washer.

I definitely have something else that's shorted. I didn't realize the diode I replaced was on a dual layer part of the PCB so I fixed the connection on the top and as soon as my bridge rectifier was intacted I powered it up ( with the bul limiter) and straight away burnt out the two diodes on the negative side of the bridge.

OK the problem is with the diode I replaced I think I destroyed the solder pad a little any tips on how to repair it?

OK VL is not there as its for a foot pedal. My model isn't compatible with one.

OK done some testing and I've found.

+3.3V
+HI
+9
Are all good.
-HI and -9 are missing
Can't find yes points for +VL yet.

Cheers mate I have the spider 3 but I think the basics supply should be near identical. I'll have a look.

What a pain. If I could look at the diagram it would be much easier to test the diodes as they are all numbered on the board. I'll give it a go though with my trusty pen and paper

Quote from: Enzo on March 12, 2015, 05:03:48 PM
So find out where the negative supply went, nothing works without good power supply.  If only +20 is applied to the IC, then all that can appear on its output is +20.

Thanks for the help, doesn't seem as terminal as I first thought when I saw smoke come out

Does anyone have a schematic for this amp? I can't find one. I'm confused with all the diodes as I thought you only need 4 for a full wave rectifier not 8. Or do they have 2 DC voltages? 1 from the center tap of the transformer?

I also have +20V DC on the O/P pin (pin 4) the inputs all have less than 1 V