Tracing noise problem, TwinRev.

[Sea Chief]

I wouldn't unplug any of the load. Since you'll be poking the preamp components you could remove two power tubes (one from each end of the OT as discussed) AND unplug one speaker. That should quiet it down a little and you'll still have a matched load.

Good idea. Ive got cab against wall, & boards on the back too.

Firing up again, all tubes in back in/ 1st time since recent tests.. it behaved alot better this time. Now whether this is a momentary thing, or more positive ( but of course boards on back tamping the volume ). . I can't tell.

It may well be next time I fire it up, the prominent gremlins are going again.

Anyway Im preparing with a wooden thin paintbrush, to go 'a pokin. Me no likey. Thx SC

[Chuck H]

I hope you find one or two components that scare the $h!t outta you when you poke them. That's the whole point of this.

[Sea Chief]

I hope you find one or two components that scare the $h!t outta you when you poke them. That's the whole point of this.

fk a duck Chuck.

[Chuck H]

I will.
Remember to poke at the pot lugs and tube pins too. Good luck.

[Sea Chief]

I will.
Remember to poke at the pot lugs and tube pins too. Good luck.

No don't Chuck.. i meant uk expression ' fk a duck! ' ( IE ' bloody hell!' ). Ok Im diving in tonight. Bloody thing.

Chuck, does the pulling of v4 & the noise stopping, decisively / definitlively conclude the problem is in the preamp stage?

Or not neccessarily so/ other possibilities could produce this noise stopping @ v4 ?

I wonder if my tests - have- proved anything at all you see.

Thanks, SC

[Chuck H]

Yes, because pulling V4 stops the noise I'm suspecting the circuit from input to V4 only for the moment. Definitive? Probably (Probably definitive! Is that allowed?)

Otherwise we're still at an early stage because of side steps, like the low volume with just the normal channel tubes in and relatively few actual tests so far. But if you poke a component or connection and get pops, snaps, crackles, sharp onset of hum or any audible signal then you'll at least have found "a" problem that can be fixed. "The" problem? Hope springs eternal.

[g1]

does the pulling of v4 & the noise stopping, decisively / definitlively conclude the problem is in the preamp stage?

Or not neccessarily so/ other possibilities could produce this noise stopping @ v4 ?

What other tubes were installed at this time?
In post #98 you said with only V1, V6, and power tubes, the noise was there.

[Sea Chief]

What other tubes were installed at this time?
In post #98 you said with only V1, V6, and power tubes, the noise was there.

I was going along pulling, so v5,6,7,8,9,10.

thx SC

[Chuck H]

And this is why I used the "probably" caveat for "definitive".

[Sea Chief]

And this is why I used the "probably" caveat for "definitive".

Ok well that's a good sign then. I will get chopsticks from thriftstore tmrw. Thx sc

[nosaj]

Ok well that's a good sign then. I will get chopsticks from thriftstore tmrw. Thx sc

Just order Chinese and be done with it.

nosaj

[Chuck H]

Just order Chinese and be done with it.

nosaj

WOW! I miss the Chinese food in San Jose, Ca. You can't throw a rock in the Bay Area without hitting a GREAT Chinese or Mexican restaurant. Good times for that end of things. Living on Whidbey Island is really great in it's own way, but if you want Chinese, Mexican or Indian food you're absolutely out of luck here. Seattle is the only destination (two hours minimum). You can get good Chinese and Indian there. But Mexican food!?! Well, A lot of people will tell you "this place" or "that place" but compared to east side San Jose taquerias there's just no comparison. I'm talkin' guy in a sombrero napping in the corner, there's a chicken running around and you have to pigeon your way through the language barrier because your the only gringo in there. There's just no comparison anywhere and I guess I'm spoiled by it.

But I'd settle for some really good Chinese in town for sure.

[Sea Chief]

pdf64 Quick I can ask idiot Q's whilst Chuck & Co are asleep. Then I can edit them before he wakes up so it looks like Im cleverererer.

Pete, if reasonsbly sure if not certain the noise stops when v4 pulled ( going along, one by one, all tubes in until i get to v4..), & Im ready with chopstick to tap board components, is the idea at this juncture to put v3 back & concentrate my tappings around the general area of the board wires from v4 socket, IE general adjacent components? Or general V3 & V4 areas?

Or is it now a case of putting all tubes back, & incrimrntally working my way along from 'start' of board, each component?

Thanks. SC

[pdf64]

V1,2 and 4 are all served by the same HT node. And from what I can make out, there’s noise if V1, or V4 or V2 and V4 are populated.
From that, I suggest to get tapping around the feeds common to those circuits, ie HT and 0V common. With valves just in V1 and V6, to reduce the variables.

[Sea Chief]

V1,2 and 4 are all served by the same HT node. And from what I can make out, there’s noise if V1, or V4 or V2 and V4 are populated.
From that, I suggest to get tapping around the feeds common to those circuits, ie HT and 0V common. With valves just in V1 and V6, to reduce the variables.

Hi pdf, remind me what a HT node is would you?

Yesterday am I did some general poking/ prodding with v,1,2,3 removed. most things up to the two big board orange drops, up around the power tubes.

Nothing obvious to report. Hmm.

Ok then I got an odd situation: I put all tubes back apart from v1. Poked. Nothing. Amp was mostly behaving in fact, mild distortion only. Then put v1 back in, LOUD crackling, pops etc back. Pulled it out whilst on ( Im so brave now ) small 'pop' & noise stopped ( only mild background noise again).

So this now pretty definitively surely, signifies something in / around v1. Poked again here with tube back ( brave me )... nothing.

---

One other odd thing. I notice a sort of innervingly 'current' feeling to the knobs, worst RHS ( intensity) getting progressively less, IE felt less as you go alongte knobs. Ive not noticed this on any amp before, probably like it during the tests before, but Ive not picked it up.

Also/ last thing to note, is a loud hum ( groundy type ) on the reverb knob, gets worse as you turn it up, quiet at zero.


Thanks, SC