Tracing noise problem, TwinRev.

[Chuck H]

HT node would be the power supply rail junction that supplies voltage to V1 plate resistors. So this would be the lead connections to the V1 socket plate pins from the 100k resistors, where the two 100k plate resistors for V1 join at the high voltage lead and also the + connection at the last filter capacitor under the dog house.

I just perused the whole thread again looking for something specific. It has not been mentioned that a different preamp tube was ever tried in the V1 socket. Have you tried a different preamp tube in that socket or have you been consistently putting the same preamp tubes in their respective positions? ie: "V1 is this tube" "V2 is that tube", etc.?

With just V1 and V6 in place, if you haven't tried more than just the one preamp tube in the V1 socket then you should. Any of the other pulled tubes will do. And...

If a different tube is quiet and has proper volume again for the normal channel then it's probable that the original tube that was in V1 is bad. If a different tube in V1 doesn't fix the problem then you may have bad tube pin contacts in the V1 socket and/or one or more cold solder joints associated with V1.

Not that "I" was the one on que at this time. But there's my $.02 FWIW

[Sea Chief]

HT node would be the power supply rail junction that supplies voltage to V1 plate resistors. So this would be the lead connections to the V1 socket plate pins from the 100k resistors, where the two 100k plate resistors for V1 join at the high voltage lead and also the + connection at the last filter capacitor under the dog house.

I just perused the whole thread again looking for something specific. It has not been mentioned that a different preamp tube was ever tried in the V1 socket. Have you tried a different preamp tube in that socket or have you been consistently putting the same preamp tubes in their respective positions? ie: "V1 is this tube" "V2 is that tube", etc.?

With just V1 and V6 in place, if you haven't tried more than just the one preamp tube in the V1 socket then you should. Any of the other pulled tubes will do. And...

If a different tube is quiet and has proper volume again for the normal channel then it's probable that the original tube that was in V1 is bad. If a different tube in V1 doesn't fix the problem then you may have bad tube pin contacts in the V1 socket and/or one or more cold solder joints associated with V1.

Not that "I" was the one on que at this time. But there's my $.02 FWIW

Hi Chuck. Before I posted the thread I made sure I had swapped v1 & ruled out this possibility. That's all I could do/ my input.

I never label the tubes ( 12 ax7 ) & swapping around the symptoms remain suggesting cannot be tubes, or rather liklihood almost entirely ruled out.

I will now look at v1 socket/ pins though. I did resolder all of board's v1 area, & topside of v1 socket pins. No change.

thx SC

[Chuck H]

Ok. Sounds right so far. As to the V1 socket, I'm concerned with how well the little cups in the socket are contacting the tube pins (or not). This can sometimes be managed by cleaning and re tensioning them. They're usually made like a split tube that has a little spring to the metal. Sometimes you can use something pointy and thin to sort of push them back together again. And sometimes they're just too fatigued or oxidized to be saved and you have to replace the socket. Sometimes solder and/or flux gets into one or more slots and messes things up. You can try cleaning the socket to remove oxide or debris, but not solder. Cleaning is usually done by dipping the tube pins into contact cleaner, inserting that tube into the socket and gently rocking it a little to sort of scrape the tube pins against the tiny tube walls. Then use the pick to attempt re tensioning. Be sure all the contact cleaner has evaporated before turning the amp on.

[g1]

Early on it was reported that Ch.1 was a certain volume with all tubes installed, then Ch.1 had significant drop in volume when V2 thru V5 were removed.
It would be useful to know if this is still the case.

[Chuck H]

Early on it was reported that Ch.1 was a certain volume with all tubes installed, then Ch.1 had significant drop in volume when V2 thru V5 were removed.
It would be useful to know if this is still the case.

Yes, there's some issues here. Right now it looks like tube pin contact? SC reports all solder contacts for V1 have been redone. Going sideways always seems to create a pause in any current line of approach in THIS particular case. But the volume issue with channel one is still on my radar. That is to say...

Maybe we fix one problem, amidst other problems happening at the same time. Excess hum in the reverb circuit has been reported as well. I'm ignoring this for the moment. In this instance I'm not assuming that all problems will be related to the same , singular circuit fault.

[g1]

Going sideways always seems to create a pause in any current line of approach in THIS particular case. But the volume issue with channel one is still on my radar.

My concern is still whether we have a valid schematic or not, as this is essentially a 'build'. If the ch.1 volume drop (only when V2 thru V5 are out) is a constant, we either have a gross wiring fault, or an invalid assumed schematic. If the latter is the case, all troubleshooting goes out the window.

[Sea Chief]

Early on it was reported that Ch.1 was a certain volume with all tubes installed, then Ch.1 had significant drop in volume when V2 thru V5 were removed.
It would be useful to know if this is still the case.

Hi g1. Great point. Im away for the weekend, so can answer this/ doublecheck if anything different on this monday evening.

Thanks.

[Sea Chief]

My concern is still whether we have a valid schematic or not, as this is essentially a 'build'. If the ch.1 volume drop (only when V2 thru V5 are out) is a constant, we either have a gross wiring fault, or an invalid assumed schematic. If the latter is the case, all troubleshooting goes out the window.

Hi Chuck.

But this issue solving, is based upon the known fact that once I rebuilt it ( some ' black face' mods added, many components just renewed like the 6l6's & their sockets & roach & new filter caps, a choke added, & a little reconfig of the rectifier were all that were changed... not too much tbh ) it worked great. Really nice, quiet, lush reverb, a bit more general 'character' than the stale stock UL 135 beastie.

So no schematic as such, or rather an amalgamation of two really.. in principle.

Rift amps oversaw the reconfig 'design' along the way, with a fair bit of thought. Then we tested properly.

I'll go over & concentrate on v1 really thoughrally reading your prior post ( grateful 4 info there ) on monday. Report back. Thanks, SC

[nosaj]

Hi Chuck.

But this issue solving, is based upon the known fact that once I rebuilt it ( some ' black face' mods added, many components just renewed like the 6l6's & their sockets & roach & new filter caps, a choke added, & a little reconfig of the rectifier were all that were changed... not too much tbh ) it worked great. Really nice, quiet, lush reverb, a bit more general 'character' than the stale stock UL 135 beastie.

So no schematic as such, or rather an amalgamation of two really.. in principle.

Rift amps oversaw the reconfig 'design' along the way, with a fair bit of thought. Then we tested properly.

I'll go over & concentrate on v1 really thoughrally reading your prior post ( grateful 4 info there ) on monday. Report back. Thanks, SC

Yes but say your going to London and youve never seen it before. And you have someone on the phone who has been there(but many years ago) but is working off memory on how to get you there. Now they don't know the road has changed or there are detours to be taken. And when you see something you don't quite describe it correctly because you don't quite understand what your seeing.

A proper schematic is just as valuable as a proper up to date map. Which no one has it seems.
nosaj

[Sea Chief]

Yes but say your going to London and youve never seen it before. And you have someone on the phone who has been there(but many years ago) but is working off memory on how to get you there. Now they don't know the road has changed or there are detours to be taken. And when you see something you don't quite describe it correctly because you don't quite understand what your seeing.

A proper schematic is just as valuable as a proper up to date map. Which no one has it seems.
nosaj

But this is like the conductive board red herring.

If it was working great after I built it, or rather rebuilding iit 95% the way it was, the fact is through usual trial & error fault finding, the fault should be able to be found regardless of my (or rather Rift's) 5% deviation from the stock UL 135w SFTR, & I should be able to get it back.... simply to working great again.

And, the original schematic is 95 % of use too. So for all intents & purposes, if the current fault - seems possibly- to be located in the preamp, & the preamp is 95% the same as a stock UL135w... it seems churlish to say " cant fault find his amp, bc its not 100% stock to the UL 135w design".

It seems like an excuse to give up offering help to me; like the conductive board determined hypothesis was, which turned out -it seems, though not definitively concluded as such- not to be true after all.

SC

[Sea Chief]

Could anyone help on this finding..

When I warm up tubes with heater circuit, IE before engaging the standby switch to the "up" position, I physically feel an unusual prominent 'electric current feel' to the Intensity knob. In fact all Vibrato channel knobs. But diminishing in strength as I go along, so at Volume knob, it's only just felt.

I am surprised to feel this odd, rather disconcerting physical manifestation touching the knobs ( like a strong 'alive' feel to the knob, slight juddering with steong voltage or currwnt... or something) both when the amp is fully turned on, & also, beforehand when just the power ON switch is engaged, tubes heating up etc.

Could the 6.3v heater circuit, I wonder through naiive logic only, be "crossing over" or " leeching" somewhere over to the main circuit-? I mean why would I feel the " alive " feeling Intensity knob touching it, before the amp is actually fully on? IE when only the heater circuit is engaged.

Thanks, SC

[Helmholtz]

Make sure the amp is properly safety grounded.
Measure resistance between amp chassis and earth contact of mains plug. Should be zero.

[Chuck H]

Helmholtz is placating your observation here. I'm not saying that someone couldn't perceive such things, but it does seem unlikely. His advise on the matter is sound though. There's no reason, ever, to NOT test something if you have the information to do that.

Meanwhile... You have spun a new dilemma at the cusp of finalizing a solution to a specified issue without having complied with said finalization. Hmmmm.?. I feel like we've been here before.

How about we use this thread to solve the issue at hand and THEN start a new thread about sensing current in the knobs and what that might mean.

[Sea Chief]

Helmholtz is placating your observation here. I'm not saying that someone couldn't perceive such things, but it does seem unlikely. His advise on the matter is sound though. There's no reason, ever, to NOT test something if you have the information to do that.

Meanwhile... You have spun a new dilemma at the cusp of finalizing a solution to a specified issue without having complied with said finalization. Hmmmm.?. I feel like we've been here before.

How about we use this thread to solve the issue at hand and THEN start a new thread about sensing current in the knobs and what that might mean.

Sure thing Chuck. It was just mentioned because it is concerning, from a safety angle. Safety first etc.

If you say it's safe to carry on trying to find original issue before looking at this, fine. I'll just check mains earth tho.

----

I have super-cleaned & re-tensioned v1 pins, swapped in 3 known good 12 ax7 's again ( redoing this check for 4th time ).. & I still get the crunchy noise BUT it seemed to be less, no loud pops. But as it was intermittant before, I'm not confident I have alleviated anything/ made any difference.

Noise was heard too with v1 pulled ( amp sort of starts reasonably quiet, then the noise creeps in, getting worse ).

So I will do a super-clean of all other preamp tubes' socket pins now, & re-tension ( all 45 of them ).

ThX SC

[Sea Chief]

Make sure the amp is properly safety grounded.
Measure resistance between amp chassis and earth contact of mains plug. Should be zero.

Hi HH.. thanks I'll check this asap. SC