Static, Crackle and Pop

[Fahrner]

No, this has nothing to do with what I had for breakfast.
Also, this has nothing to do with the foot switch. It is unplugged and bypassed.
After the amp is on for a while, especially after its been played, it develops static and crackle and a few pops.
It's sporadic. It will be quiet for a while and then go noisy and get quiet again.
It started about a month ago. This is a combo.
Have removed the effects loop cables and engaged the efx bypass switch.
It occurs on all channels and all power modes. It occurs in both rectifier and diode mode. It occurs with no external cables plugged in, including the input.
I've replaced all the tubes except the rectifier (Dougs tubes).
I've had the amp for maybe 2 years (new).
It reminds me of a Fender Super Deluxe Reverb I once had. It developed this kind of crackle due to a defective batch of plate resistors. They would develop fractures and would start to separate when they heated up. I replaced them and cured the problem. This sounds just like that if that means anything to anyone.
Not sure what else to try so any fresh new ideas would be greatly appreciated.
Next step is back to the dealer but what a pain.

 

[Chester]

I had a similar issue recently, but for me it was speaker cable to the head. Changed that and I've not had any problems since.

You've already knocked off the fixes I would have suggested. Sounds like a dealer solution as you suggest

Good luck

 

[Adambomb]

I am having the same issues. Except mine usually does it when I first start playing but comes back maybe within 5 mins. Static and pops are on all channel, all modes of power and tone. I'm thinking maybe the phase inverter tube which is the last preamp tube (I think).

 

[Fahrner]

Adam, mine can act the same way.... like the problem is aggravated when I start playing. However, it will also make static when idle.... with the input unplugged and standby is on.
Some of the other things I tried;
Many of the jacks are used as switches. I exercised all of them several times with a dummy plug/cable. My thinking was one of the contacts may have gotten dirty like some guitar switches. Like wise I worked all the rotary switches several times.
I wiggled the speaker cable and jack trying to re-create the static.
My first thought tube-wise was the power tubes since they are under the greatest stress.
The only tube I've not replaced is the 5U4. That I will do come Tuesday. While the static also occurs in diode mode, after studying the schematic I'm not convinced it's not still in the circuit; just not the power tubes. BTW if anyone knows different, please let me know.
My advice is to eliminate everything else before you go on a tube swapping spree. They can be a bit of a pain to get to, especially for this near 70yo. Flipping the amp over on its top makes it easier.
If you do find the cause, please be sure to post.
Good luck.

 

[Fahrner]

Good news!
Replaced the 5U4 yesterday.
Four hours last night and another three hours today.
All quiet as a church mouse (though I've never really heard one).
So the static and noise was coming from the rectifier tube.
Wouldn't you know it. The thing that fixes the problem is always the last thing you try.
Next time I'll try working the list in reverse order.
Cheers.

 

[Adambomb]

Good news!
Replaced the 5U4 yesterday.
Four hours last night and another three hours today.
All quiet as a church mouse (though I've never really heard one).
So the static and noise was coming from the rectifier tube.
Wouldn't you know it. The thing that fixes the problem is always the last thing you try.
Next time I'll try working the list in reverse order.
Cheers.

Ok man thats good to know it fixed your amp. Seems like alot of people are experiencing the same problem. Maybe they got a bad batch or rectifier tubes. Which brand tube did you go with?

 

[Fahrner]

Adam, it happened to be a JJ 5U4GB, though I don't think the brand of the rectifier tube makes that much difference. It was the most reasonably priced and fastest availability.
While I have the effects loop hooked back up I still have not plugged in the PITA foot switch. While it's a beautiful thing in all that it does with a tap of the toe; I still suspect it as part of the problem.
All that buzz and chatter until you select a channel just cannot be a good thing. I know I've switched the amp on (in standby) and left the studio for a few minutes to come back to the thing chattering like an old erector set ferris wheel project gone bad. (how many people remember that?).
As I read through all the posts about folks having noise problems, the foot switch seemed to be the number one cause albeit simply a bad connection.
I don't think that there's a rash of bad rectifier tubes as in my case. I think the true noise static issue (not relay chatter and buzz) can be caused by many possibilities. I got lucky in that I didn't have to lug the beast down to the local shop or ship it off to MB.
Also, have had the amp for 2+ years. It was time to change the power tubes at least.
Adam, did you get your problem fixed?

 

[fr0sty]

My mark has been spitting and making other annoying noises. Changed the power tubes and now it's quiet as can be.