Rebuilding an old tube amp --- I've got some questions.

[anthony691]

I have an old (early 60's) Lectrolab R600 amplifier. It is all tube and has (2) 12AY7, (2) 6V6, a 6SJ7, and a 6X5.

 

How can I find out the wattage?

 

The cabinet is very poorly constructed and it won't withstand much of any abuse so I want to yank the electronics and build a new case for it without modifying the original case or the electronics.

 

In the new case, I want to put in a new speaker because what it has is a really trashy Nichols that I don't really enjoy. Can anyone reccomend a good speaker for this application? 12", I don't know what power it would need to be rated for. Should I use two speakers, even? Because I'm building my own my own case for it, pretty much anything is possible.

 

Thanks,

Anthony

[guitarcapo]

I think if you assume it's a class A/B amp
because it uses two 6V6 tubes. If so it would probably be around 22 watts a la a Fender DeLuxe. If it's class A I would speculate about half that. A more precise measurement would involve measuring the plate voltage with a meter and the current with a bias probe. If you multiply these two numbers you get the power dissipation of one tube at rest...which is usually biased to 70% of maximum dissipation...So multiply the numbers...then double the value because you have two tubes, and then devide by .7 (assuming that's how it's been biased) to get the maximum output.

At the end of the day you have a number that really isn't that valuble.

[marder explorer]

You should change all of the electrolytics in there, just for safety's sake, and you'll be a lot better off from a reliability standpoint.

As for speakers, pretty much anything will work, just depends on what kind of sound you are going for. If you use it cranked up and distorted, a "Euro"-flavored speaker like most from Celestion would do you fine, and not be so bright on the ears at louder volumes, or a little bit smoother. If you use it for clean tone mainly, then an "American" speaker like most from Weber would suit you.

That amp won't be pushing more than 20 watts from 2x6V6s.

[anthony691]

I was wondering about the ohmage of the spears --- I don't know anything about that. I think I want to go with two 8" speakers.

Any advise there?

[anthony691]

Well, I think my quest is at least temporarily over.

I opened it up, and much to my chagrin I found it to be covered in rat feces and the caps were physically chewed up. I thought the old tubes were what made it growl so foullybut I guess it needs all new caps.

How much do you think a pro would charge to redo all the caps?

Thanks,
Anthony

[marder explorer]

If a rat has been in there, you don't want to keep any of the stock components. Corroded contact points, especially grounds, can be a nightmare, and it'd be better to start afresh with all new circuitry. Expect to pay quite a bit to have a tech do it all for you.


Personally, with all those tube sockets, I'd either rebuild it to the stock setup, or make my own circuit from it (in your case, have a tech do that). I'd shy away from 8" speakers, especially if you are used to a 12 inch speaker's heft of sound. 2 8's will never have the bottom end that 1 12inch does.

[anthony691]

Thanks, that's pretty much what I was thinking. It is almost a shock that the thing still works.

I'm thinking of selling it and buying a Fender Blues Jr.

I don't know how much I could get for it being honest about the damage, but on the other hand it does function... Probably enough to take my halfway to a fender blues jr.

Thanks,
Anthony