Amp trouble

TerrorStorm

Member
Messages
23
Ok, So I recently powered on my amp and after a few minutes of playing I get this weird fuzz/static sound. It's not always constant and usually takes a few minutes before it starts to kick in. I've been able to troubleshoot it enough that I know it's not any of my cables or pedals. Any ideas what this may be, or do I need to just take it in somewhere.
 

8len8

Silver Supporting Member
Messages
13,594
I had a similar problem and it ended up being bad/cold solder joint that got worse as the amp heated up.
 

vintage66

Member
Messages
6,658
tubes. If it's a tube amp that is.
That's the first thing to check and hope that's it. Otherwise, I've found it's a b*tch finding an amp tech that can troubleshoot worth a crap. Seriously, I usually get my amp back making the same sound I took it in with. Part of the problem is you take it in, talk to them, they hopefully scribble something down, then 2 weeks later they try to remember what you told them was wrong with it, can't remember, charge you for something that didn't need to be fixed, give it back still broken.

Like I said, hope it's tubes.
 

AXEnGEAR4J

Member
Messages
5,901
Ok, So I recently powered on my amp and after a few minutes of playing I get this weird fuzz/static sound. It's not always constant and usually takes a few minutes before it starts to kick in. I've been able to troubleshoot it enough that I know it's not any of my cables or pedals. Any ideas what this may be, or do I need to just take it in somewhere.
> Make sure you check the pots well
> Remove tubes several times, use a contact cleaner if possible
> Check input jacks
> Check internal grounding
> Possible faulty filter caps
> Noisey plate resistors

Some other things;

A good way to divide and conquer is to turn the volume control(s). If the hiss changes levels as you do this, then the source of the hiss is something that affects the stages of the amp before the volume control. A faulty, hissing preamp tube will be turned up this way very quickly. Conversely, if the volume control does not affect the hiss, the cause is somewhere after the volume control. In general, the volume level of the hiss is an indicator of where the hiss is occuring - the louder the hiss, the more likely its source is near the input of the amp where the gain applied to it will be the greatest
The procedure of locating by removing one tube at at time working from the phase inverter/driver back towards the input until removing a tube no longer stops the hiss should then localize the problem to one tube's worth of circuitry.
 
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TerrorStorm

Member
Messages
23
So should I just swap out all the tubes myself and hope that fixes it. Then have it looked at if needed?
 

Rocknhorse1

Member
Messages
135
It's always good to have spare tubes around for this reason. It makes trouble shooting easier. The Chinese tubes that come with my new amps get removed as soon as I get the amp. I put them in a box, and use them for trouble shooting if needed.
I just had a brand new set of KT66's start hissing and squealing, and motor boating on me right out of the box....biased, and didn't even get my guitar plugged in...done. I have had this happen with preamp tubes as well...mostly new production.
 

TerrorStorm

Member
Messages
23
Alright, last question. Suggestions on tubes?

Spec sheet is as follows:

  • 1-12AX7 Tung-Sol (Russia)
  • 5-12AX7AC (China Selected)
  • 2-Premium Matched Sovtek KT88 Power Tubes
  • 1-Premium Tested 5U4G (Russia) Rectifier Tube
Get the same brands, Sovtek, etc. Or does TGP have better ones in mind?
 




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