twin reverb re-tube? speaker swap?

[neosadist]

All,

Recently I discovered that my 1972 Fender Twin Reverb has been altered. It has Celestion Modern Lead speakers. Also, some of the tubes have no label on them, no etching, etc, to identify. I'm wondering what other things someone has changed on it. The 6L6's are JJ's, and I've been told that they're inferior to either Fender or Groove Tube....
But here's the real question. Do you think I should swap the Celestions back out for the Jensons? For lack of knowledge, I'm going by what the '65 Fender Twin Reverb Reissue uses. Also, the tubes should be the same number and type, right? Is there any way to really check the tubes with basic electronic supplies?
And should I decide to actually swap the tubes out, do you guys recommend the Fender brand ones, or should I go with Groove Tube? I was looking at the '65 reissue and some tubes are Groove, some are Fender. They were replaced about a year ago....
Thanks guys!

Robert

 

[BigDaddy]

Re: twin reverb re-tube? speaker swap?

Ok..........sounds like you are a little clueless.....no offense, but back up and do a little research. JJ tubes are some of the best on the market, fender tubes are some of the worst and Groove tubes are overrated. Those Celestions are great speakers that could probably handle the power better than a pair of C12N's.

First take it to a competent repairman and have him go through the amp.

Here is what I would do:
1- retube with high quality tubes and rebias.
2- replace "all" the electrolytic caps, especially the filter cap and bias cap.
3- replace all resistors that have drifted well beyond their values and caps that are leaking.
4- make sure those speakers are 8 ohms so you have the correct load. It should be 4 ohms total, 2 8ohm speakers in parallel = 4ohms.
5- make sure everything is to stock specs
6- pay attention to lead dress and the twisting of wires especially the heater wires. Fender started getting sloppy around that time.

NEVER retube without a rebias. Never do anything to amp if you do not know what you are doing. Worst case scenario is you will fry your amp, even worse would be death because of electrocution or you start a fire and burn down your house.

Once the amp is setup to stock according to the schematic and all the parts that are questionable are replaced, than make a judgement on what you want to do with it. I'm sure once that is done you will find the amp sounds really good and nothing else has to be done.

If you have no idea what I am talking about you really have to read up on this stuff. Just google it and you can have anything explained to you. If you want to contact me that would be fine, I will try to help you in anyway I could.

But Please do not do anything to that amp yourself.

 

[neosadist]

Re: twin reverb re-tube? speaker swap?

Yeah, I'm clueless as to where to begin troubleshooting a tube amp, because I don't know how to test tubes. But as for electronics, I am USAF certified in component repair, so I know what not to do and such. However, the limit of my abilities with home equipment is to test things with a multimeter (Fluke variety). I don't have the ability to test capacitors or tubes. As for resistors, hopefully they have the value on them, or else I'd have to look up the color bands (but I can do it).

I'm guessing the previous owner replaced the tubes but didn't have it rebiased. I'd have to take it to a shop to have that done, so I'll do that. I know someone who knows someone.

But thanks! Oh, and by the way, if a twin reverb is 85w-100w, why am i seeing descriptions on google of the speakers I have yet they are rated 75w? Sorry, but if I see that they're not rated as high as the stock Jensen C12K's (100W), and the Jensens are for a more sweet clear clean sound while the Celestions say that they're for stock marshalls and that they're for hard rock / metal, I'm starting to wonder. That's what made me think that maybe I should choose something else. I need to be versatile, and about half my time is spend in hard rock, the other half in bluesy or even clean jazzy sounds.

Does anyone else have an opinion?

 

[neosadist]

Re: twin reverb re-tube? speaker swap?

Nevermind. I talked to Lew for a while and evidentally the JJ's and Sovteks are good tubes, and the Celestions I have are better than what came stock. However, now I need to "blackface" my amp, as I don't see any adjustments on it for biasing the tubes, and it has different tubes. I'm thinking the previous owner just changed tubes and nothing else. Also, I'll be sure to have it serviced and I'll be sure to get the stuff done, in terms of testing and replacing the caps as need be. With military grade stuff this time .

Thanks all.