I'm looking for ideas. My friend's Fender Rumble 100 was working one day and the next day it wasn't. I told him that I would open up the amp and look for something obvious but I didn't see anything suspicious. On the normal channel, with the Gain and Master full up, it barely passes the sound of the guitar. On the Overdrive channel it is extremely noisy; so much so that it can't be used. And, as one starts to push that lower "vintage" tone button you can hear that loud beep tone. Plugging into the Effects Return jack yields a guitar sound that's fixed; a signal that isn't affected by adjusting the Gain, Volume or tone controls. I'll try to post links to the scheme and a short video.
Video
Schematic

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I'm working on my Peavey amp and I need to replace a few 3mm, 3-leg LEDs. In ordering, I have a choice of common cathode or common anode. How would I determine which I need?

Hi. The amp is a three year old Peavey Vypyr. The amp started smoking and the breaker in the power strip it was plugged into tripped shutting everything down. I've determined that there is a short inside the 3Amp IEC EMI filter. You cannot view this attachment.I've found a replacement online that I can order that has the exact same specs. I also found 1A, 6A and 10A rated filters with almost the same specs. The one spec that is different is the inductor spec. My questions are: Is the inductor used in that device what determines the device's AMP rating? And, would there be an advantage with using a replacement EMI filter with a higher (or lower?) AMP rating for this application?  Thanks.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.     

Although I have an identical working board I'm going to try to repair this burned circuit board. This resistor (R55) is small and my eyes are getting old. I see brown, grey, yellow, gold 180K 5%, or maybe red, grey, yellow, gold 280K 5%. And, does this cap look suspicious? The cap on the good board looks much "cleaner".

Hi. The forum has helped me in the past with amps but now I have a problem with a car radio and maybe someone can help me. This inexpensive car radio has had a capacitor burn up. It looks like it took out the 1000uf behind it too. I have plenty of 1000uf caps in my stash but I don't know the value of the burned cap. However, the cap around the other side of the 1000uf is a 104 (.01uf). Is it likely that the burned cap is also a 104? In my stash I found three different types of 104 caps. Which type would you suggest that I use as a replacement? Thanks.

Hi, I've been lurking here for a few years and have enjoyed reading the repair topics and learning a little about solid-state devices. But now I find I need diagnostic help for a problem that doesn't involve a guitar amplifier. I'm hoping that someone can point me in the right direction with this non-amp problem but I will understand if this isn't the proper place to post. I just had my little powered bookshelf computer speakers go kaput. Suddenly and with no prior warning they started squealing and buzzing. And they do this even after unplugging them from the computer. The 15vac power supply tests OK and I don't see any obvious damage on either side of the board. I am going to include a link to a short video that resides on Google Drive so you can hear what I'm talking about.
https://drive.google.com/open?id=1mw1AzFlJktfG7W-b3fgpAxluKt4s-HGD

Hi...My Peavey Vypyr VIP 2 started buzzing and crackling a gig tast week. It reminded me of what it sounds like when a speaker is about to fail. When I got it home I swapped out speaker but the problem remained. Tried different guitars...same thing. After I turn on the amp it takes about fifteen minutes of warming up/playing before I can induce it to start buzzing. It is induced most easily when thumping on Bb or B note on the E string. Near the end of the clip I play a C note and the buzzing/crackling goes away. I have tried to attach a 1 min. 15 sec. sound clip:

I had this TRUE or FALSE question on a written test recently: You can change the resistance in a circuit that uses a 520ohm 1w resistor to 608ohms by adding four 22ohm 1/4w resistors in series to the existing 520ohm resistor.

I answered true but now I'm not sure of my answer.

What's the deal with unplugging a guitar cord while the amp is on and the volume is up? I've seen some people panic if the volume isn't turned down first. But I've heard some people state that "it doesn't matter with a SS amp; it's only important with a tube amp."

I bought an inoperable 2001 Studio Pro 112 and quickly found the damaged LM 3886t. I've removed the 3886 and I am ready to order a replacement. Is there anything/anywhere else I should look for related problems?

I'm cleaning up an amp of mine and what appears to be white lithium grease was used between the two heatsinks and the back panel during the factory assembly.  I'd like to know exactly what kind of grease this is in case I need to renew it before reassembly of the chassis.

After having a look inside a Peavey Studio Pro 40 amp, I see that the speaker connections come directly off the circuit board.  I don't see an output transformer where a 4 ohm tap might be found.  My plan was to add a switching jack for an 8 ohm extension cabinet.  Am I missing something?  Is there a 4 ohm tap somewhere in there?