diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Solid State (http://www.diyaudio.com/forums/solid-state/)
-   -   power section pops like frying bacon (http://www.diyaudio.com/forums/solid-state/213895-power-section-pops-like-frying-bacon.html)

Pbassred 4th June 2012 09:14 PM

power section pops like frying bacon
 
I am attempting to repair a guitar amp that belongs to a friend of mine. I isolated the power section and power supply from the preamp and tone controls. Its making random pops and crackles as if I am wiggling a loose connection. The power supply is a simple unregulated bridge rectifier and 2 caps. The amp is a TIP35 and 36.

I have re-soldered all of the component connections and changed all of the electrolytic caps with no success. What you recommend next?

moschfet 4th June 2012 09:41 PM

Hi Pbassred,

this could be a cold solder joint.

Ian Finch 5th June 2012 12:21 AM

.....Or a deep-fried semi, assuming you have no sound. Did you have some output before dismantling?. If not, run a DVM over the base emitter junctions and verify there is ~0.6V across each. junction.

wg_ski 5th June 2012 02:45 AM

Highest on my suspect list would be the input transistor(s) of the power section. That is, the one that follows the tone/volume control section. That's where noise from a bad transistor or cold solder joint would bother it the most and be noticeable.

Pbassred 5th June 2012 06:26 AM

It works properly as an amplifier. I had already reflowed the solder joints so it can't be a cold joint. I'll swap the input transistors and see where that gets us.

indianajo 5th June 2012 11:41 AM

Although the other causes are more likely I am sure, I had a frying bacon noise (low) on both channels in a power amp from some tantalum input caps (5.0 uf) I installed. Caps were purchased at RK distributing, a local parts store. Had it from the day I activated the purchased dead amp until 20 years later when I replace the caps again. Wasn't any internet in those days, didn't know what to expect from a transistor amp. This replacement time I used 4.7 uf 50V CPO ceramic caps. Much better! Still have the OEM (original equipment manufacturer's) 1970 transistors on one channel.

sbrads 5th June 2012 01:29 PM

Freezer spray is good for helping to find such faults. Apart from joints and caps, don't forget resistors. I've seen lots of usually high value (>47k) resistors go dodgy after several years if the leads are bent close to the body.

DF96 5th June 2012 01:43 PM

Reflowing joints can make them worse, while at the same time hiding the evidence by giving them all a nice shiny appearance. Bad joints should be redone, the rest left untouched.

jitter 5th June 2012 04:17 PM

Quote:

Originally Posted by wg_ski (Post 3048515)
Highest on my suspect list would be the input transistor(s) of the power section. That is, the one that follows the tone/volume control section. That's where noise from a bad transistor or cold solder joint would bother it the most and be noticeable.

Perhaps this amp suffers from popcorn noise. If that is indeed the case, I would suspect a high gain circuit.

Ian Finch 5th June 2012 05:09 PM

I think that popcorn noise is intrinsic to the device. i.e it would have sounded that way from the time of manufacture.


All times are GMT. The time now is 08:30 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2