[quietglow]

Hi all, hoping someone can help out with a problem which is driving me nuts:

My SE84C has a noise problem. Randomly, it'll emit a buzz/rustle that sounds sorta like the sound a volume pot makes when it's getting scratchy. This will last from anywhere between a couple of seconds and several minutes. It does not seem to be related to whether things are warmed up or not. It's coming from both channels. Touching the exterior of the amp, turning the volume pot and wiggling the tubes does nothing to change it. When it first started, I though that switching the bias switch would quiet it, but I was never positive.

What I've done: replace both output tubes (it needed them anyway). I found several posts around the net which suggested that the bias switch was prone to problems (and it's in the signal path) so I removed it. Switched out the rectifier tube as well.

I have reasonable DIY skills, but I've never done troubleshooting on something very intermittent like this -- it reminds me of diagnosing an odd noise in a car. Any suggestions as to how to proceed would be very much appreciated.

[Speedskater]

Did you rule out interference?
Can you take it to a friend's house and try it there?

[Guy 13]

Hi quietglow and all Audio Circle members.
I have a Decware SE84C+ but I can't be of any help, because mine is dead silent.
If you solve the problem, you will enjoy a very good SET amplifier.

Guy 13

[quietglow]

Did you rule out interference?
Can you take it to a friend's house and try it there?

Actually I haven't ruled out interference, though I do have another amp (a Dynaco ST70) that has never exhibited the problem in the same location etc. Not sure if that counts as ruling it out, though.

[Speedskater]

Well my Dynaco ST70 was an excellent interference receiver!  But then interference was a lot different in 1970.

[nature boy]

Suggest you contact Steve Deckert directly at Decware.  I am sure they will resolve your problem, great customer service.

NB

[quietglow]

Well my Dynaco ST70 was an excellent interference receiver! 

Yeah, that's what I was thinking actually. Though I think I just don't notice when it's humming because, you know, it's always humming.

[quietglow]

Also, I wrote email to Decware earlier in the week and haven't heard back yet. If I don't hear anything today, I'll give them a call tomorrow.

I thought to post this hear because I just turned on the amp this morning, and the buzz fired right up doesn't seem to be leaving. I'm actually moderately happy about that since it'll be much easier to diagnose the problem is something actually fully fails.

[Guy 13]

Also, I wrote email to Decware earlier in the week and haven't heard back yet. If I don't hear anything today, I'll give them a call tomorrow.

I thought to post this hear because I just turned on the amp this morning, and the buzz fired right up doesn't seem to be leaving. I'm actually moderately happy about that since it'll be much easier to diagnose the problem is something actually fully fails.

Hi quietglow and all Audio Circle members.

Nothing worse than an intermittent problem.
It's the same thing with your car.
You go to the dealer and when you show him the problem,
it's not there, it's gone.
Grrrr
Well, may I say that I am happy for you that the problem is not intermittent anymore, Steve will find faster the source of the problem.
Good luck.

Guy 13

[nature boy]

Also, I wrote email to Decware earlier in the week and haven't heard back yet. If I don't hear anything today, I'll give them a call tomorrow.

I thought to post this hear because I just turned on the amp this morning, and the buzz fired right up doesn't seem to be leaving. I'm actually moderately happy about that since it'll be much easier to diagnose the problem is something actually fully fails.

I would call, they have a small staff and big order backlog, so most of the time Steve's on the bench building amps.

NB

[quietglow]

It's the same thing with your car.

It really is the exact same problem. It's the reason I haven't been poking around in it more: diagnosing an intermittent problem is more frustrating than hearing the hum.

[Ericus Rex]

Pop the top and carefully inspect all the solder joints, especially those around the tube sockets.