I think Juan made a great point that looking at the components of the amp is not gonna fix it in most cases.

If I was to question one two things by your pictures alone it would be by the double potted tone potentiometer and those two IC chips(not sure what those are right of the Tone Clipping pot...) I think they are IC's I have an RG80 combo but it does not have that component there so I have no idea what it is used for... Anyway that thing looks cracked or something...

Another thing thing is the green 1KV 202M signal cap looks like the leg has torn and might be leaking... But that is probably not the problem but still can be replaced later on. However, I know that those ceramic caps when the legs are torn can cause a huge loss to signal overall. Not always the case but something to chew on just by looking at pics.

My advice is download the schematic from this link below... Look for post from Stratorius for the Schematic info then go right below his post and READ ENZO's post. Now we can assume you completely removed all the solder from the joints of the main Filter caps... I hope. Just reflowing the solder may not be enough... If not do this now as it points to loose solder joints on the caps. Change the caps too as they are nearly 25 years old.>>> But this might be the link you were looking for too.??>>>

http://www.ssguitar.com/index.php?topic=1673.0

Also, in addition to asking for the schematic which I think I will try to ask them myself too. Where did you purchase this replacement kit? I mean I saw on that first site that there were no more kits available... That would be nice for others to know where you bought this... a link...

I definitely interested in the schematic to this board and anyone here too. You did Great work on this amp Captain. Could not do it without the great techs here (they know who they are) but you also played into the factor of the amp repair being successful too! Yup standing on the shoulder of others should feel great no matter how high you rise.

If I was buying the guitar amp as I do wanting to resell the amp I would give you $20USD. If I then sold it to someone who was actually going to use the amp I would ask $40-50USD.

P.S. I pay about $5-10 for broken amps too! Not much but if it is broken and you don't want to or know how to fix it, then it is worth something to both parties. I compare these amps to the Epiphone ep1000 which is usually a tweed Korean amp that sounds actually rather nice.

http://www.amparchives.com/album/Fender/Schematics/slides/Fender%20Squire%2015%20Schematic.html

What sort of skills do you possess? Do you have DMM? Do you have skills soldering? Etc.... Etc... Etc...

This is a very simple amp to learn on and can be fixed without much money invested in parts. Look at the PCB board for bad solder joints on the filter caps or anything else that might look suspect. If you have a DMM (or any multimeter) test for DC Voltage at the speaker output leads. Test voltage on the BR or rectifier diodes/filter caps. Also, test voltage on the opamp chips. Basically, we need you to be able to take apart the amp and understand how to do these tests to help fix the problem. As Loudthud has stated it is probably the output transistor that is fried. So, test to see if you are getting voltage on the speaker output leads first to make sure.

My final thought is that 3 FETS will not get the job done here on this replacement circuit. However, I have a question as to whether J175 Q1 plays into the that role of making the logic of the switch come to life?

Looking at the datasheet pin 1 is ground...

Pin2 is marked as "A" on the data sheet, it ties over to the base of Q1 J175 and I think you should look at the transistor there to makes sure it is sound. Perhaps is was Zapped out of the circuit too!

Pin3 and Pin4 are tied together which is S1 and S2 tied to Pin 6 and Pin7 S1/S2. This is the switch.

So that leaves out pin5 and 8 as voltage carriers.

Looking at the picture pin1 and pin2 on the chip PV replacement (refer to picture) look like these ones to me, but not quite sure of this as a fact. Just a hunch after looking at it and studying it's layout. So, one channel is shorting to ground maybe due to the Q1 malfunction. To me it would seem that sure the pin out could be different on the replacement it is for a 604 chip but not DPST. Maybe this is only for SPST type switch and needs some modifications? Not sure I know exactly what I am saying here... Maybe even typing something silly will cause someone more knowledgeable to explain what could be going wrong here...?

Also, the more expensive other module you saw on that site is discontinued and really was the kit version to build what you have now. So, that is not reason why this won't work.



http://www.ti.com/lit/ds/slas042/slas042.pdf

Edit: Too funny a double posting... Also, you said on the main board there was nothing tracing anything to pin6? Explain which pins are what according to the picture... Also, show a link to the other module you thought it could have been. I might even have DPST thing wrong and it is as Juan said a "SPDT" type circuit needed. These things always confuse me at first... Or rather as Juan really put it... "Two independently driven SPST switches" Now that the solution here...

Makes you wonder what happened to that amp!! LOL    :trouble

Good job troubleshooting ya guys!! I look forward to the end result of a guitar passing signal through the amp soon.

Sorry to interrupt into this great thread... I am really enjoying reading along following all of what is being looked at on the schematic.

I have a question that even the OP might have wondered as well... Can we take voltage tests off of pins 4 and 8 on all the op amp chips? I mean sure we can test voltage there to check but why would that not prove to be useful numbers?

I am following the idea of IC2 being lifted first and then checking IC7. I think something is telling us that +/-24V rails could have something tied into the problem too. Maybe looking at Q2 and Q3 closer(later on down the line of course) and D8 is in there too. IC7 is giving me that gut feeling even more now. Also, have we confirmed what is measured on the 24v rails? Excuse me if I missed something there, but just had to ask. Good luck on this amp and I bet you nail it soon!

I was thinking the same thing but I never go full voltage until I go through dim bulb test stage first... However, I think there are times that full voltage will blow something up that a lamp bulb tester might not...? In that case maybe those parts are now out of the way once replaced, but if those parts are ones you just replaced... Well then S happens...

Geoffb have you been using a light bulb limiter at all?

Yeah I almost thought the Stage 100-160 was the right schematic too...   

I think if I was wanting this schematic to work on this amp I would divert my attention to this web page here...

http://www.fender.com/support/articles/fender-guitar-and-bass-amplifiers-owners-manuals-and-schematics-hard-copy-archives

This is a very subjective question... I think personally I never liked the reverb on any tube amp that I have owned. I guess that might be why your asking this question. The horrible part about it is that I never tried other reverbs and just stuck with what was there on the amp. However, I do love reverbs on solid state amps much better but not in regard to playing in a band. I love the reverb effect of solid states when practicing in low key environment on my own(no drums or whole live band). I think if I was gonna slap some reverb on it then I would choose a Boss reverb pedal or a Lexicon reverb rack mount unit. All this is subjective but reverb in tubes is a hard thing to get just right.

"Either side of common" is common ground. Read on and reference the schematic as you read too. Look at the P4 connection on the schematic and observe what is on each side.

To find the GNDA reference it is found all over the place on the schematic. In this case look at the power supply part of the schematic where it shows TP3 TP4 etc... On the PCB board you will find a center tap part of the transformer that is connected by way of the P4 faston. That is essentially ground or GNDA, and also you can pull out the DMM to test continuity to ground. Do the test for continuity to ground with the amp off to become familiar with all these point that reference back to ground. The chassis is a reference to ground as you will soon discover. I would get some alligator clips to clip the black probe of the DVM to chassis ground. Look on the schematic and find common grounds to double check it is connected securely. Look for the AC safety ground wire that is bolted to the chassis... That is ground reference point. With amp off clip one probe on P4 and touch the other probe to safety ground clip on the chassis. Do this with the continuity setting of the DMM and you will see .002 or something very close to zero ohms. Most DMM's have a beeping noise that lets you know there is continuity too. So, what are you noticing?

You will need to have the amp on to test for voltage. So secure that black probe to chassis ground and then use red probe to touch the test points to read voltage. Read as much as you can about safety tips before you proceed testing a live circuit, especially if this is your first time.

The thermal compound is old and used by now for over a decade. I would take some isopropyl alcohol and some Qtips to really get that stuff out of the way. It is important that this compound fill in the cracks that may exist between the heat sink and the chassis. Fresh grease is way better and more reliable. The last thing we want here is for the output transistors to overheat.

Keep up the good work and let us know if the soldering makes any difference on the amp. Good luck.