Tubes: internal schematics and such

[Robert Delahunt]

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.

Tubes? Supposedly right before I bought it, a year ago. Biased? Don't know if it was done. Old? 1972. Cap job? Not sure, but the underside of the head has a small panel that I opened, and the caps looked new. If I can't afford to maintain the tube amp, it's only for now, as I'm awaiting tax return and such to pay off a debt. I've paid off around $20,000 since I joined the service 7 years ago, so it won't be long before I can afford this amp.

Tube amps are worth it. I've never played a modeler that I liked.

 

[ErikH]

Re: Tubes: internal schematics and such

Since it appears that you use this amp quite often, the tubes should be changed at least once a year, biased when they are changed and then check the bias again 6 months or so later. The bias could drift from normal use and just from the tubes normal wear and tear. The caps in my Marshall look new and they're 17 years old. The look from the outside of them can be misleading but if they look "new" new, they're probably OK. Doesn't hurt to have that verified by a tech though.

Yeah, tube amps are worth it. You have to try the Vox Valvetronix amps. Totally forget what your Twin sounds like and come at it from a different angle.

 

[B Bent]

Re: Tubes: internal schematics and such

below is an example of what old/bad filter caps look like. These were in my 1975 Vibrolux. If yours look brand new that's a good thing. If they look like the ones below have them replaced. Also look at the ends of the caps (DONT TOUCH THEM THOUGH) if you see stuff leaking out of them you really need to change them pronto!!!!

 

[ES350]

Re: Tubes: internal schematics and such

Replace all those resistors on the filter board as well...

 

[Robert Delahunt]

Re: Tubes: internal schematics and such

below is an example of what old/bad filter caps look like. These were in my 1975 Vibrolux. If yours look brand new that's a good thing. If they look like the ones below have them replaced. Also look at the ends of the caps (DONT TOUCH THEM THOUGH) if you see stuff leaking out of them you really need to change them pronto!!!!

Yeah, mine look newer, like the light-blue-plastic-shrink-outside models. I don't know if they're for this application, but they seem to be newer. Sure, however, what I'll do when I finally go on my vacation time (30th of this month) is start ordering military-spec high-durable high-wattage components identical to the ones in my amp, one by one. I am certified on point to point wiring / soldering, and getting flux and a good iron will be worth it for this. I also know how to drain capacitors.

Do any of the tubes themselves act as capacitors, by the way?

 

[bungalowbill]

Re: Tubes: internal schematics and such

Do any of the tubes themselves act as capacitors, by the way?

Try reading this

http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm

 

[ES350]

Re: Tubes: internal schematics and such

Sounds like you have Sprague Atoms for filter caps---those are prolly good, change out the dropping resistors on the filter cap board with metal film types. Leave the tone stack caps alone unless you want another flavor. There are quite a few other things that could give you a low output in an otherwise functioning amp---the 25/25uF bypass caps on each channel, for instance. If you mean---do tubes retain a charge like caps, the answer is no.

 

[B Bent]

Re: Tubes: internal schematics and such

Yeah, mine look newer, like the light-blue-plastic-shrink-outside models. I don't know if they're for this application, but they seem to be newer. Sure, however, what I'll do when I finally go on my vacation time (30th of this month) is start ordering military-spec high-durable high-wattage components identical to the ones in my amp, one by one. I am certified on point to point wiring / soldering, and getting flux and a good iron will be worth it for this. I also know how to drain capacitors.

Do any of the tubes themselves act as capacitors, by the way?

How do I say this without being a butt?????? Well no offense, but IMO if you asked a question like that you have no business being inside that amp!!! And I mean that in the best kind of way.

 

[liquidtension]

Re: Tubes: internal schematics and such

I also know how to drain capacitors.

Run a wire from each end to your tongue and feel the presence of the spirit!

(please don't actually try this)