Well it is good to have the pictures online so everyone has an idea to see the Rat's nest we are working on here. I love Polytone amps but looking inside of them it is always a wonder how they sound so good... I follow all the advice given thus far from Juan and others... However looking at the pics I have to question what caused the browning of the circuit board here... Did you inspect the traces on this part and test the mylar film cap for any damage?

yeah dude go sleep at that point!! I hate when crap like that happens, as it is like the World Wide Web is against you!! Don't worry man it all works in the end... or so I was told too  :trouble

You can also rely on fileden.com for upload of these files, as it is a simple to use file server site.

Why not add some pics to this thread. For one I would like to see a pic of the power supply circuit. It helps to have these pics of the amp out here online for all to see later down the road too. I think we need to start at the power supply and work out the voltage readings through the amp. Lets figure out where on the circuit they create the lower 15v rails (i.e. dropping resistors).

Hey Roly! I had read this on your page a while back and it was a great read. My favorite line you wrote... "I have developed an idea over years of faultfinding (ranging from mine safety to Intensive Care) that the real problem is you, not the equipment. The fault simply is what it is, just lying there waiting for you to recognise it. It isn't hiding, or being difficult, it's just that you haven't looked at it yet in the right way to see it."

That is a really well put statement!  :dbtu:

I am still dying to know the outcome here... Don't give up is my best suggestion. Replace that one part to get it out of the way and as Roly say's "isn't the cause of the problem" Come back and let's get this thing figured out.

If everything else is looking great then it probably is the problem. I mean it looks like a little critter came up to it and took a good bite out of it. While you are soldering a new part back in it would be wise to take a good look at other solder joints to re-flow. However, you might just want to change out that part first, then test it. That way you know exactly the outcome of the bad part in relation to the amp repair. There still could be other problems to address so take it slow and methodical.

Trust and follow all the advice Enzo and Roly give you here!!  That advice is right on the money... Build the Light bulb limiter before anything else that you do... Unless you like blowing fuses... Read all the posts have been sent and follow up before you move forward...

Edit: There are many others here that give great advice too!! Just named Roly and Enzo as a starting point. There are many others here too and you need follow their advice to the T to get the most out of your repair process.

Well how well will that original track mix with a drum track or bass line? Where is the objective other track with the new sound(peavey amp)? Personally, it is all merely subjective tone. I mean seriously what do you have over-driving the guitar? Just USB interface into some sound card? What sound card are you using? What bit depth? Sample rate? Direct in with solid state technology is really a nice sound to a certain degree, but hence you must understand that in comparison to tube amp sounds. Tube amp distortion or overloading into a square wave is nice with a touch of compression and EQ too. Really what is your question here today? Square wave all the way or what overdrive, fuzz or metal distortion pedal would be best on your front end? I am at a loss to advise you on your own tone for a guitar part really.

I know that you like the sound of the original guitar... But what is all this lower level signal? Send me the file and I will add some Noise Reduction plugins. I will make your original guitar part come out more and have less noise when you are not strumming. That is if you drop the guitar track by 6db to give a reasonable amount of headroom. It is all just a demo I know but your tone has been found. It just needs to be cleaned up a bit.

It seems to me that you like this original approach to creating demo's... So just keep doing that if you like it... Still when you are done with the demo's what sort of recording plan do you have in mind. I can think of ideas where you could go but at least let me download your track and mess with it a bit for fun. Please if you do send a copy of that guitar turn it down 3-6db for some feasible headroom.

Well I may have played the fool in regards to how the TL604 chip functioned in this amp. However, I think that Q5 is not getting the correct voltage there on the drain. I did look at the schematic and start to question Q5 and Q6. Q5 would be my bet for testing and/or replacing.

The analog meters are worth keeping for certain things but nothing like a very accurate digital meter. I am very jealous of your other amps you are working on!! Sounds like fun!  :dbtu:

Quote from: Roly on May 22, 2013, 01:57:39 PMI suspect that something has failed in IC3 which is loading down the switching circuit and preventing the other FET's from switching (despite the correct LED indication).

After reading through this thread I get stuck on Roly's thought here... So if IC1 is working as the switching FET that leads over to IC3 TL604, hence leg 2 AD/DA is working on IC3. Then shouldn't there be signal that is routed through S1 and S2 through that IC? Which leads us through to Q6 and Q7 and that circuit for the distortion channel. It all leads us back after that to the R5 connection. I am not sure what I am alluding to here, but really just have questions. I want to understand this circuit better as others here can explain where I might getting off track with my questions.  8|

Got to respect someone when they know their limits to working on electronics. However, if you were ever going to learn about amp repair then this is a great starting point to learn. To be honest this type of repair can be very straight forward. A meter does not cost very much for a basic Digital Multimeter and a solder iron can be had for around $10-20. Building a light bulb limiter is very easy. Mainly testing the output transistors and some of the associated circuit for damaged parts is very easy. Taking the whole thing apart and the careful soldering of replacement parts is really the hard part.

Learning these skills have really helped me fix a lot of amps and I am really a primitive repair guy. If you have the drive to learn then just realize that there are always great people here to help too(as you must already know). The techs on this site & a few other websites are really great teachers of amp repair. Then again you really have to WANT to learn or have the time to do so. Good luck  :tu:

Your gonna need one of these by the time you figure out where to plug all the transformer wires onto the pcb board. Light bulb limiter!! Very important...
http://www.ssguitar.com/index.php?topic=2093.msg22315;topicseen#new

This links to a thread on here that has the schematic and some similar troubleshooting scenarios.
http://www.ssguitar.com/index.php?topic=1040.0

Got to look at that schematic for some clues where to place the transformer wires. We can see on the schematic that CP3 and CP5 are for the secondary wires from the PT. CP4 would be a center tap if there is one, my guess there is one. CP10 looks to have the hot side of the mains as it is fused and then travels back out after a thermistors(think that is what that is) through CP9 to the primary of the transformer. Wait for others to confirm this as I am not 100% on this...  To figure out those wires we need more info as I made an assumption we are running on 120v here. Where are you located, which country? What are the colors of the wiring on the power transformer? I am guessing there are 5 wires or are there any other ones? Let us know or take some pics for references, good luck.

The output and input resistance seem to be good. However, very strange to see pin 3 on the 4558 chip return nothing. Can we blame the reverb unit? I don't think so yet. I am not the best person on this site to make any assumptions, but my guess is something is lost in translation. I hate shotgunning the parts and I know everyone with greater experience would say the same. However, with the readings you have from the reverb, as far as resistance, it would be guess to swap out a known good 4558 chip in this instance to rule out a bad opamp.

Edit: I guess I could have read that you did that already whoops!
Still jump back to JM's post "The switcher Fets will turn on and off following what's on RC4558 pin7 ,
Do Leds indicate switching condition?"

You also typed "Somewhere in the preamp area?
Anyone had problems with the TL604CP?
The "Treble/Pull Ch. Select" does select the channels."

Does that answer his question here? What do you exactly mean by that statement?

Still not sure where the problem is... Possibly the RCA jack needs to be looked at on the output side of the reverb unit. Assuming you ran signal directly into pin 3 to test the op amp... Since now your wondering about jumping the signal across the reverb tank, right? So maybe it just a bad RCA cable connecting from the output of the tank to the return circuit.