Funny thing is I had to call Fishman for a schematic recently too and it was just the fastest phone call ever. I love companies that support their products at the consumer level so the owner has options for independent repair. Makes ownership a privilege rather than an inevitable headache that comes with trying to repair something without the roadmap.

Quote from: Enzo on July 11, 2017, 08:56:44 PMWhenever I have to replace outputs, I change the drivers, yes even if they test OK.  They are getting stressed by the power transistor failures.  And your meter puts a tiny current at a low voltage through the part.  The circuit puts substantial voltage on the parts and draws substantial current through them.  Your meter can't test for that.

Amen to that one brother!! The idea is that you are already in there so you might as well. With amp repair we constantly hear don't just replace parts such as throw in a new set of caps before isolate and fix the REAL problem. But when you have transistors near a point of failure it sometimes pays off big time replacing those questionable parts. I owe a lot to the pro repair guys online as I just know to replace those pre-drivers after a major failure. Their experience saved me from finding out the hard way many times.  :trouble

I recently had to call Fender for a schematic a few weeks ago and it was very quick & easy. However, he did mention something about how he only sends it if the person sounds like they know what they are doing. Seems like I did good job fooling him!!  :duh

Quote from: aaron on June 20, 2017, 03:14:53 PMWhat I ended up doing was cannibalizing a small heat sink from another circuit board, applied thermal paste, attached it to the resistor, and voila!

I'd like to see a picture of that.

Quote from: aaron on June 14, 2017, 02:48:28 PMThere's no way that those resistors should be that hot.  I was wondering what to do, and I decided to check out the voltage vs. what it's called for on the schematic.  I don't know why, but the AC voltage was less than half on one side, and like a fourth on the other side of what it's supposed to be

Please explain exactly what measurement you are talking about and relate that exactly to the schematic so we have a chance to understand better. Be detailed oriented in you explanation. Example-----> "I put black probe on chassis ground (earth) and the red probes was connected _________" Fill in the blank....

Just got to be sure we are approaching this the correct way. Check major DC voltage check points on the amp, main power rails and low voltage supplies.

Clyde I can't see a link or anything it is just white space...??

This is a test of the google drive posting. Attempt with img tag... Plus I set google drive image properties so it is public too.(directly below this img tag was used to post image file link)


Now Hyper-link test with same file....
https://drive.google.com/file/d/0B8JIpzle0qeRRVdTeHVFUVVWeHc/view?usp=sharing

Also below you can click attachments of saved images from your computer below. So why not just do it that way from the start instead of hosting the image on google drive or some other website. Then if you delete the image from google drive it won't disappear from the site here.

Previewing it ahead of clicking post show the img tag is not showing on my post.
Edit: however later they might show up as they did in the original first post of this thread but like a day later and as a hyper link. But that must have the OP going back to change the tags from IMG to URL.

Quote from: aaron on June 08, 2017, 04:53:20 PM
I don't see how not using half the amp's channels increases my options.
I was hoping for electronic advice....

Our advice is given based on what questions have been asked. It will take a bit patience with us to remotely help you as we are not there to observe the amp directly. At this point I only mentioned touching up solder joints since you had taken the amp apart already and observed some solders that looked questionable. From the start we would not have advised to start by removing the circuit board. Once the amp is put back together then the electronic advice will get more in depth and the community here will help as much as we can. Best regards.

Quote from: aaron on June 08, 2017, 06:06:46 AM
I still can't embed images from google drive....
clicked on "insert image".....nope
clicked on "Insert Hyperlink".....nope

https://drive.google.com/open?id=0B7FTDBmMiEfcV0ZiT3Z3V2JzUGM
All I had to do was to copy paste link between url tag code. [url][/url] Sounds like you tried but perhaps it is a result of being a new member here. We had problems with people joining the forum only to post a spam url link. I am not 100% certain but as a result Joecool (webmaster) could have set it up so new members would have to post 5-10 posts before allowing members to post links on the page?

Edit: oh never mind I just noticed it is now working in the original post and I see the links, nice!

Quote from: aaron on June 07, 2017, 02:43:23 PM1. The reverb makes a sizzling sound (fizz?--imagine the sound of frying eggs)....The higher the reverb know is dialed, the louder the sizzle.Any idea which component would cause that?

Now when the reverb is dialed to zero, the clean channel works fine, sounds fine, etc.

The board around the reverb knob definitely looks funky, the solder connections look dull, there's brown goo, etc., so I guess it's time to sort out which part is bad and replace it.  (BTW, the reverb tank tests fine, and the reverb WORKS). NOTE: This was hidden inside message but I don't think other's will see that he added this image... https://drive.google.com/open?id=0B7FTDBmMiEfcV0ZiT3Z3V2JzUGM

Is this something that has recently developed or has it been this way since you have owned the amp? The brown goo you mentioned sounds like it is left over flux residue which is commonly found from solder joints. Best to clean it up and re-solder these joints while you have it out. Looking at the picture attached it appears that dull solder joints could be cold soldered connections. Remember it does not always have to a bad component that needs replacing and could be just a bad connection. Also, that picture of the board shows a trace clearly lifted up probably from someone soldering it too many times and/or with too much heat applied. Inspect all the solder joints looking for not only dull looking cold connections but also any cracked joints too.

Quote from: aaron on June 07, 2017, 02:43:23 PM3.  The large "cement block" resistors and two diodes in the power section (I think) are clearly overheating and the solder connections on the board are clearly dull and blackened.  There's a bit of brown goo there too.  The two large caps look OK, and the solder connections look fine, but there is a bit of brown goo...I'm not sure if this is a leakage from the neighboring overheating or not.  The parts that appear to be overheating are: CR25, CR26, R94, R95, R42, R43, C24, C25.   C48 and C49 also look abnormal on the underside of the board. NOTE: Another picture was hidden here in the text that could not be viewed....https://drive.google.com/open?id=0B7FTDBmMiEfcbDBqQlA2V3FtWVE

Those are cement wire wound resistors and they drop voltages, most times to the preamp circuits. They do get hot and they do overheat the circuit boards over time creating a browning of the board itself. In fact, those diodes in the picture it looks like they heated up leftover flux residue on the top side of the board and it has turned dark brown. Clean all that brown flux residue up while in there with a alcohol and a q-tip. All very normal and you should focus your energy right now to your very first question about dull looking solder joints and the possibly damaged circuit board traces.

COMMENT: Please attach your google drive images as url hyperlinks rather clicking image tag or we won't be able to see them on the post. Thanks. :dbtu:

Also, check the Marshall MG30RCD schematic attached here to see if any similarities between your amp. Such as does it have a TDA2050 chip for the output stage?

Could be the first opamp on the market that the component itself is actually repairable? That was the only benefit I could think of for this thing. Repairing that thing would be a pain in the butt too. Still easier to just grab another opamp and just replace it.

Perhaps Q9 went first and took all the others with it? Have you tested Q9 yet? Also test Q2-Q4 if you have not yet and even those diodes D13 & D14.

Also +1 for using GIMP, great program!!  :dbtu:

 :dbtu: Yup your program makes it so much easier to translate a schematic into a layout when designing an amp. Thank you so much for this great software!!

$35 for a pair of transistors is not a happy price to pay for me, and I do not consider that to be a "cheap" price. Before I went and ordered new outputs I would surely check to see if they were truly fried.

No problem running an amp on a light bulb limiter to avoid an issue on first power up and it takes no time to do this.

From my past experiences Enzo's logical questioning should have been something I had already tried or figured out first. It can be challenging when someone, with such deep wisdom on the matter, points out very logical questions regarding a post. Someone new to this whole thing might incorrectly take it as just criticism without intent to help. Sometimes we need someone to point out the hard truths, even bluntly. So I am guessing the "PITA" comment might have been made sort of tongue in cheek?