When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

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As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Sorry, I know it's not a tube amp, but this seems to be the only amp repair subreddit.

Looking for some help with my bass head. There is no sound coming out of the 1/4" jacks. The xlr d.i. works. I don't have a cable for the speakon out so I can't test that one. There is signal going in, I know because I can crank it and trigger the clipping light.

Reading online a few people suggested cleaning and jumping the power amp out/in or the effects loop. I did that and the amp worked briefly, until I turned it off. While it was working, it only worked with the power amp in/out jumped. When I insert a cable to the 1/4" out, there is sometimes a little "pop" when it becomes fully inserted.

I opened the unit up and the 1/4 jacks are making good contact. It feels like the output jacks, but seems unlikely that both wouldn't work if they just need replacing.

Someone said online that there's a contactor that's engaged when the effects or power amp loops are jumped, so perhaps I need to replace that?

Any help would be appreciated. Thanks!

I have a working concept for a small 2 Channel 15-20W Guitar amplifier with either a 6V6 or EL84 power section and the option for both Cathode or Fixed Bias.

Of the 4 or so amplifiers that this design is based on, 2 have an LTP Phase inverter (1 with Negative feedback and 1 without) and 2 have a Cathodyne/Split Load Phase inverter (again 1 with NFB and 1 without) and I am interested in the idea of being able to switch between either PI topology (the LTP would consistently have negative feedback as both channels are mixed before the PI.

My primary question is could this be achieved with a single twin triode and a switch with a great deal of Poles to change which circuit it’s connected to, or is this better suited to having 2 separate PI circuits with their own valves?

I’d appreciate any input that you might be able to provide, as I am still finding my way in the world of tubes.

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Soooo yea, this happened with Ei El84 tubes. I don't know why because the JJ El84 work normal. The far right one got so hot I thought it was going to melt.

Took the chassis out of my dsl20h and accidentally tore part of the shielding foil in the cabinet, only a small line about a cm wide and 5cm long. Don't think I noticed any extra buzzing after turning the amp back on, possibly a bit more feedback than normal but telling myself it's in my head. Should I get it fixed or is it fine? Will I run into any problems?

Hey folks, I am designing a simple push pull amplifier, inspired by the Fender Bassman 6G6B tube guitar amplifier. I don't full understand how to couple the preamp section to the phase inverter and hoping somebody may be able to offer some guidance and/or examples of schematics for amps similar to what I'm going for. I've included a schematic for the amp I'm designing.

What I have seen before, is usually either one of two ways. Sometimes I see a resistor(approx 15k) between the 100k plate resistor for U1b and the B+ line. That couples to the "upper" input of the phase inverter through a .01uf cap.

Another way i see if usually in a two channel amp, and there is no extra 15k resistor. Instead, there is a 220k resistor from the plate of each preamp tube, connected to a .01uf coupling cap.

I'm going for a no master volume amp, and in my head, I feel like the best option would be to use a voltage divider consisting of something like a 470k resistor and a 16k resistor, that is connected between V1b plate and the PI input with a .01uf coupling cap. However when I do that, and I run a test in LTspice, I am not seeing any signal from the 2nd PI input at the inputs to the power tubes...?

Most of the values on this schematic are "ball park" only, so please keep in mind that this schematic is not final by any means. Any and all help appreciated! TY in advance.

https://preview.redd.it/7j7uma6xd6ee1.jpg?width=1721&format=pjpg&auto=webp&s=cc18fa37ac45025398b7772fc3787b0322a2c9d8

Trying to find shielded wire not in 100+ ft spools has proven to be difficult. Trying to find single core 22 AWG shielded wire for a JCM800 build and everything seems to come up flat. I'd love to get multiple different colored external insulation and teflon/high temperature insulation. Where do you all get your shielded wire from?

Hey guys, I've been wanting for years to do a short run of amps for some people I know (because if I'm already building one, why not build three?). I've been changing things here and there, but the one thing I haven't done was figure out where I'm going to source internals.

I've already heard of The Tube Store, but I'd rather have some options just in case something doesn't work or if someone wants something done different. The best prices are another thing I'd appreciate as well, whichever is best for each thing.

I'm not looking to profit, maybe just cover the cost of my own with a small labor cost each, so if you have a secret source you don't want made public you can feel free to message me instead. I'm not in the business of hurting anyone's business :)

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

My first tube amp builde (modified 5e3) is coming along nicely. I have a question regarding why pin 2 of rectifier reads 110 VAC in respect to ground, but 5.5 VAC with respect to pin 8.

I have wired up the power, fuse, pilot lamp, filaments and high voltage secondary. So far so good I think! (The board is not installed, just loosely fit for parts spacing).

Last night I decided to try a "glow test" and to check voltages to make sure I haven't encountered problems.

The board in the picture is not actually installed yet. I put center tap of HV and 6.3 v green filaments to ground (using input jacks I right side of photo.

I plugged in, powered up without tubes to make sure pilot glows (it does). Then install tubes and they glow nicely. I check voltages and get good reading everywhere except an unexpected result at rectifier tube.

At this point I have my digital multimeter grounded to chassis via alligator clips and am probing around. Approx 330 VAC at pins 4 and 6 on rectifier. 110VAC on pin 2 (with respect to ground) and 280 or 300 or something like this DC on pin 8.

Then I unplugged the tube and probed and got pin 2 at 15 VAC with respect to ground. I was stumped until I realized I have to probe with pin 2 in respect to pin 8 with no tube in and I got 5.25 VAC.

Anyways....why the 15 v at pin 2 and 8 with respect to ground instead of 5? Is this because there is no center tap on the 5v windings? What am I observing here?

Thanks for the info.

Sincerely,

Electronics noob

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.

Hey guys

Hoping someone has experience with Mercury Rectifiers here!

I'm designing an absolute monster of a guitar amplifier at the moment, 30W single-ended powered from a pair of 866A Mercury Rectifiers.

The power amp will demand something like 400mA peak at full-load, so the usual glass rectifiers are out of the question. I want to use the 866As over a silicon bridge purely for aesthetics.

Because of the high current though, I'm worried the mercury rectifier is going to start emitting dangerous levels of UV...Wondering how best to screen them but also keep them visible? Would a vented hood be sufficient?

Cheers

Hello folks,

I bought this transformer in a job lot along with a bunch of valve transformers and I was wondering if someone can help me identify this one.

The windings were measured using a Mustool ET4410 LCR meter @ 1kHz.

Any help is appreciated!

https://preview.redd.it/h53k12nspg9e1.png?width=2283&format=png&auto=webp&s=13c3f0da61b11a845168fe7869d3771a978ae305

https://preview.redd.it/i0s5fcrppg9e1.png?width=678&format=png&auto=webp&s=b5086b1586aca54f3fcfc874d6038c7a8caf8851

https://preview.redd.it/v0cyvcrppg9e1.jpg?width=4032&format=pjpg&auto=webp&s=e9f64876ce342673e5e2cf63b7cbc6524b547ccb

https://preview.redd.it/jz1judrppg9e1.jpg?width=4032&format=pjpg&auto=webp&s=cbdfa28dc6504a143270e436cf7b242af47684a3

When you're working with high voltage, there is no such thing as a dumb question. Please use this thread to ask about practical or conceptual things that have you stumped.

Really awesome answers and recurring questions may earn a place in the Wiki.

If you'd like to nominate a comment to be included, just reply [Wiki] (with the brackets)! The mods will be automatically notified that something awesome just happened.

As always, we are built around education and collaboration. Be awesome to your fellow tube heads.