Tubes: internal schematics and such

[Robert Delahunt]

All,

I've had some trouble looking up detailed info on tubes for tube amps: how the pin numbering system works, how to shoot ohms / continuity across the pins to verify if the tube is going bad or not. I am not rich enough to afford the $200 mass-replacement of all the tubes in my Twin Reverb, so I'm hoping to find info. The problem is lack of output power: it feels 1/4 power.

 

[B Bent]

Re: Tubes: internal schematics and such

SED Winged C 6L6's will cost you < $100 for a matched quartet. That's your problem. These are great new stock 6L6's. I highly doubt is is something else. That is a classic description of power tubes that have gone bad.

 

[Robert Delahunt]

Re: Tubes: internal schematics and such

Yeah, it probably is, but still, I want to find internal schematic info on tubes so I can shoot ohms / continuity across them (using the schematic) so I can find out if mine are bad or not. I'm not rich, and don't have the money to shell out for a whole quartet of tubes, much less the bias job afterwards. I might go Fender 6L6GC's because they come pre-matched, but even then I'm betting on them not needing a bias job.

This is why I want the internal schematics so I can shoot ALL my tubes and check them all at one time.

 

[B Bent]

Re: Tubes: internal schematics and such

Yeah, it probably is, but still, I want to find internal schematic info on tubes so I can shoot ohms / continuity across them (using the schematic) so I can find out if mine are bad or not. I'm not rich, and don't have the money to shell out for a whole quartet of tubes, much less the bias job afterwards. I might go Fender 6L6GC's because they come pre-matched, but even then I'm betting on them not needing a bias job.

This is why I want the internal schematics so I can shoot ALL my tubes and check them all at one time.

Wait.... do I understand correctly that you are buying Fender brand tubes because since they are Fender brand tubes going into a Fender amp then you won't need to have the amp biased?



If so...... :smack:


Also all brands can be purchased in matched sets.

 

[Robert Delahunt]

Re: Tubes: internal schematics and such

Wait.... do I understand correctly that you are buying Fender brand tubes because since they are Fender brand tubes going into a Fender amp then you won't need to have the amp biased?

Is that true, or false? I have no clue.

 

[jeremy]

Re: Tubes: internal schematics and such

that is not true. fender doesnt make their tubes, most of them are sovtek.
if you change tubes youll need to rebias.

im not sure you can really test a tube without putting power to it

 

[B Bent]

Re: Tubes: internal schematics and such

Is that true, or false? I have no clue.

That's what I am asking you. Is it true that you think you can buy a certain brand of tube that don't require a bias adjustment? If so you are somehow mislead.


Also I am not sure if you realize or not, but if you are experiencing loss of volume and just a generally weak sound, you don't have to replace all the tubes. Just the power section.

 

[marvar]

Re: Tubes: internal schematics and such

Here is a link to data sheets/diagrams for most of the popular tubes and types-
http://www.guitaramplifierblueprinting.com/datasheets.html
P.S. the only time you may not have to re-bias is in the case of Groove Tubes, or any other brand that has specific ratings, for example-if you have GT #7 rated tubes, you shouldn't have to re-bias as long as you replace your tubes with another set of GT#7, but I feel like it is a good idea to check bias any time you replace tubes. If there are other problems with your amp, they might show up at that time.

 

[bungalowbill]

Re: Tubes: internal schematics and such

Yeah, it probably is, but still, I want to find internal schematic info on tubes so I can shoot ohms / continuity across them (using the schematic) so I can find out if mine are bad or not. I'm not rich, and don't have the money to shell out for a whole quartet of tubes, much less the bias job afterwards. I might go Fender 6L6GC's because they come pre-matched, but even then I'm betting on them not needing a bias job.

This is why I want the internal schematics so I can shoot ALL my tubes and check them all at one time.

I believe you are overthinking this.....Buy a good set of 6L6's and have the amp biased by a good tech. If you are willing to spend the jack on speakers, why not a good set of tubes.

 

[Smilemon]

Re: Tubes: internal schematics and such

I have a pro junior. I looked into it and found out it wasn't very touchy about biasing.. I got two separate Fender (Sovtek) EL84 power tubes both rated for 7. It saved me about 25 bucks. A set of Groove Tubes Was 40 bucks. Your Amp might not have to be biased..

I know my friend ran a pair of 8's through an amp that was biased for 6's it worked fine.

How much different is it for 6L6?

Smilemon

 

[MartinSixStringCustoms]

Re: Tubes: internal schematics and such

I believe you are overthinking this.....Buy a good set of 6L6's and have the amp biased by a good tech. If you are willing to spend the jack on speakers, why not a good set of tubes.

I agree. Tubes are reasonable cheap.

 

[Robert Delahunt]

Re: Tubes: internal schematics and such

You guys have a favorite place to get your tubes? I hate to ask but I am on 12's and will work through the weekend, so I will not really have time.... I appreciate you guys!

 

[dd12939]

Re: Tubes: internal schematics and such

I've been recommended www.eurotubes.com and www.revolutionguitar.com
The guys at both places are very helpful and will answer any questions you have.

 

[Baltar]

Re: Tubes: internal schematics and such

if you are from germany or around i can recommend www.tube-town.de

dirk is a very friendly and able guy.

 

[B Bent]

Re: Tubes: internal schematics and such

I have had very good dealings with www.thetubestore.com Great customer service.

 

[aleclee]

Re: Tubes: internal schematics and such

I get most of my new production tubes from Lord Valve. He tests everything he sells so the chance of getting a bad tube is minimized and his prices are quite good.

He doesn't publish prices on his web site but sends them out via email. I keep the latest version on my web site.

 

[ES350]

Re: Tubes: internal schematics and such

You can't test a tube by 'shooting ohms/continuity' across the socket or something with a DMM...you need a tube tester. So forget that idea...If you are getting 1/4 the output you expect, I would imagine you have component problems (bad cathode bypass caps, etc etc). Take it to a tech...

 

[StrangeSound]

Re: Tubes: internal schematics and such

if you are from germany or around i can recommend www.tube-town.de

dirk is a very friendly and able guy.

Word!

 

[marvar]

Re: Tubes: internal schematics and such

You can't test a tube by 'shooting ohms/continuity' across the socket or something with a DMM...you need a tube tester. So forget that idea...If you are getting 1/4 the output you expect, I would imagine you have component problems (bad cathode bypass caps, etc etc). Take it to a tech...

This is true, the only thing you will find out about the ohms/continuity thing is if you have a dead short- in which case the tube won't work anyway. I agree, take it to a knowledgeable person, if you are short on cash, see if you can work something out with him.

 

[ErikH]

Re: Tubes: internal schematics and such

Aside from the apparent loss of power, when was the last time this amp had the tubes changed and biased? How old is it? Has it ever had a cap job?

I agree with what's been said already, you need some new tubes and I'm with Greg, get the Winged =C= 6L6's.

Now, I'm gonna share this and I mean it in a kind way. If you cannot afford to maintain a tube amp, sell it or put it away and get either a solid-state amp or a modeller that suits the needs. Tube amps are like cars in that they cost money to maintain.