Ticking problem with a 124 build

[wjdunham]

Hi guys, I'm having a strange problem that I can't seem to diagnose, I have a 124 build that has an occasional ticking that I've traced to the plate of V1B. It comes and goes, seems to be worse after the amp has heated up. I poked around with a scope and traced it back to the V1B plate. It doesn't appear to be coming in from the power supply, since that B+ side of the plate resistor doesn't show the glitch. Neither does the cathode or the grid. I disconnected the grid resistor, and the NFB and it's still there. Couldn't find anything on the heaters either.
There must be some charge building up somewhere that finds a path out occasionally, at this point it seems like it must be building up inside the tube? I tried a few different tubes all with a similar result (all JJECC83S). I don't have a gut shot at the moment, but any help or suggestions on what else to check would be greatly appreciated, this one has me a bit stumped.
Bill

[hitchcaster]

cell phone or clock or something else in the room thats doing it?

[heisthl]

Line power noise - just ask Angelop

[wjdunham]

I thought maybe it was coupling from outside, but the amp has been in a few different locations with the same problem. I have other amps that don't exhibit the problem in my house as well. I could try a big magnet on the power cord and see what happens.

[Bob-I]

Are you talking about the little tick.... tick... that happens after you've played hard, then stopped?

Everything I own does that in my house, and occasionally in other places. I wish I knew what it was, but I've gotten used to it, like the voices in my head I just ignore it.

[jelle]

Line power noise - just ask Angelop

The baseball bat story?

[Structo]

That is a strange one.

ANGE?

[wjdunham]

I did some searching this morning (not a ton, but some) and I don't get the reference
When I first heard this I thought for sure it was a piece of external equipment coupling in to the amp, as the tick was at very regular almost one second intervals. Mind you, when the amp is being played, this is a non-issue, but we happened to be at a recording studio where it was bit more of a problem. I got the darn thing home where the ticking is a lot less regular, but still there. One reason I didn't suspect that it was coming in from the power line is that it doesn't show up at all on the first gain stage, or on the B+. I can easily get the scope to trigger on the spike, and follow it from the PI to V1B plate, then nothing in the chain before that. Clean channel only so V2 is out of the picture. I started disconnecting things from the tube socket to see if I isolate it, but no luck there. Still stumped...

[Structo]

Did you scope your power line?

Probably not it since you said it did it at another location and your other amps don't do it.
Possibly one of the filter caps is charging then leaking or arcing?

Did you check it out in a dark room to see if there was any arcing?

The cell phone is a good one, I remember reading about a guy that kept getting these weird noises, no matter where he played the amp.
Thing was, he always had his cell phone in his pocket.

I stumbled into the reason one day when his phone rang and he stepped out of the room and left the phone on a kitchen counter.
Went back into his amp room and no noise!

[Deric]

A long-shot and from your description most likely not related but... If you touch the standby switch does it stop?? I built an SLO clone that had an intermittent ticking. Wasn't always there but when it was it was very regular - about every second. Touching the standby switch made it disappear. Turns out it's a common problem with SLO's. The Soldano factory fix is to remove the powder coat from the inside of the chassis where the standby switch mounts. Worked on my clone...

Good luck!

[talbany]

My first suspect would be a cap charging and discharging.. Like tom mentioned
Tony

[wjdunham]

Tony, I thought exactly that - but can't figure out which cap - first suspect was the NFB cap on V1B, but I disconnect that one and it was still there. disconnected the grid input, which took out the bypass cap across the 220K input res, but I didn't really suspect that. One thing I didn't do was disconnect the v1B output coupler, I'll try that when I get home tonight. I can also take a look at the input power and standby switch, but like I said, I couldn't find the glitch anywhere on the B+ rails.
I need to triple check the ground points in this one, maybe there's one where I didn't grind off the powder coat enough...

[angelodp]

Yes we had a strange event in the LA Venice area with a guy who had a small arsenal and some domestic issues. A small army descended on the location ( wife said he had a bomb ) and we actually got a call not to go near the area and stay inside, from the sheriffs office. Anyhow.... I lit up my RedPlate and decide to play some blues and got this tick tick fizz noise very 1.5 seconds. Henry was kind enough to help trouble shoot the amp. We tried the usual, changing out tubes, guitar, and driving my the RedPlate with my Dlite. Then we tried the Dlite and its was still there... Bingo, power source. After the bomb scare got sorted out the noise went away. Makes you wonder what the " power that be " might be doing on the grid?? It's all good.
Thanks H.

[talbany]

Tony, I thought exactly that - but can't figure out which cap - first suspect was the NFB cap on V1B, but I disconnect that one and it was still there. disconnected the grid input, which took out the bypass cap across the 220K input res, but I didn't really suspect that. One thing I didn't do was disconnect the v1B output coupler, I'll try that when I get home tonight. I can also take a look at the input power and standby switch, but like I said, I couldn't find the glitch anywhere on the B+ rails.
I need to triple check the ground points in this one, maybe there's one where I didn't grind off the powder coat enough...

Good Luck!! One other thing try cleaning and re-tensioning the V1 socket...Also temp related..

Tony

[Structo]

Ange, I wonder if the police radios had anything to do with it or possibly they were jamming cell phones so the perp couldn't call out?

Just guessing.