Show posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Show posts Menu

Topics - aaron

Hi everyone, I went to this page Same problem as mine w/ a solution, and installed this.

All it did was act as a bypass to the on/off switch, now it's always on. >:(

So, does anyone have a solution to popping noise when shutting down a SS amp?

Here's the schematic:
Hello Experts!

So I love to tinker, and my M-80, vintage 1980, has undergone the surgeon's scalpel (that would be me!)

BTW, two channels, clean (w/reverb) and overdrive.

It has two issues:

1. 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).

2.  The distortion channel has a "hum/wierdness/noise" that increases when you dial up the gain knob.  Other knobs (contour, presence, volume) in that channel don't affect the problem.

Unlike the reverb part of the board, everything looks fine via visual inspection, i.e., near the gain knob part of the board.

If there is no input to the amp, i.e., I ground/mute the strings with my hand to keep the guitar silent, the amp is silent too, no hum/wierdness/noise, diming the gain knob doesn't do anything.

3.  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.

The amp is clean inside, the brown goo is not from spilled liquid.  The electrolytic caps look good.

One point of confusion I have is if what I think are the diodes/resistors that are overheating, is the problem, wouldn't that affect the clean side too? 

So I need help with what's causing the overdrive channel to make it's wierd noise.

Can you visually inspect a "glass" diode?  CR1 doesn't look like it's neighbors on the inside.

I've attached a M-80 schematic and pics that I hope will help you help me!

P.S., I don't have an oscilliscope

Thanks a million!! <3)