Speak wisdom to me ol' great tube amp doctors in the house.

[B Bent]

I am about to pull the trigger on a 1970 SF Twin Reverb. It is pretty good shape. The guy says that it has a slight hum and a couple of pots that have static, but over all he said it sounds good. I plan on having to retube and may have to change the speakers. I don't plan on going to deep into the bowels of the amp since I am not qualified and I don't want to die. What are some good tips on cleaning up an old amp like this, specifically pots etc.? If you are interested there are a few snaps of the Twin in the link of my signature.

[Curly]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

I'd buy or borrow a copy of Gerald Weber's first book.

[kmcguitars]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

Some contact cleaner on the pots will fix the static. The Hum is most likely the Filter caps. The Filter caps are the core of the danger zone in a tube amp. You should have a Tech change Em' anyway if there 35 years old?

[Scott_F]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

How much is it? kcm is right, factor $250 into the price for new cap job, tubes and a pot or two potntially.

[HamerPlyr]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

The Filter caps are the core of the danger zone in a tube amp.

This can't be said enough times, as far as I'm concerned. I shudder to think of the number of times that, as a very young man, I took amps apart and went poking around in them with no idea that they could kill me even when they were unplugged.

Good advice, kmc. If the filter caps look greasy, have bumps on them, or are obviously leaking stuff, they need to be replaced.

[B Bent]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

I don't plan on going to deep into the bowels of the amp since I am not qualified and I don't want to die.

I was certain to mention that I didn't want to die. It's good to know this about the filter caps. I am getting it pretty cheap considering a 1970 in good mechanical shape goes for around $1000. Thanks fellas.


So Scott are you saying the cap job by itself would cost $250 or caps and tubes together would be around $250? I'm not sure what a cap job would cost. I am pretty in tune with tube cost. This would be my first hand wired amp.

[DesertRose]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

Heyz, good choice to getting a fender twin reverb. I do'nt know about the rest but I own a Fender super twin reverb also. I can't tell whether is it faulty or not, because my bright knob doesn't seem to have effect on the overall sound, but it sounds great to me. =)

If any of you know that the bright should actually give a distinctive sound on the amp, pls let me know. cuz it has NO effect, or I can't hear a difference. Thanks =)

[ES350]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

filter caps, the 25uF's on the board, some decent tubes, new speakers, correct bias, and it will last forever...have your tech check out the power tube sockets as well (it seems that a few SF amps are having problems with the sockets after 35 years)...

[Scott_F]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

I was guessing 350 total max, but you have some good techs in Hotlanta. Call and get some quotes.

7 preamp tubes 80 bucks
2 power 40 bucks
1 rect 20 bucks
some might still be good

electrolytic caps alone will run at least 25-30 bucks. throw another 4-5 caps on the board 20 bucks

conversion from silver to blackface specs 50 bucks

2-3 hous of labor 100 bucks


Owning an early 70's silverface now blackfaced... Priceless

[Marcel]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

I was guessing 350 total max, but you have some good techs in Hotlanta. Call and get some quotes.

7 preamp tubes 80 bucks
2 power 40 bucks
1 rect 20 bucks
some might still be good

electrolytic caps alone will run at least 25-30 bucks. throw another 4-5 caps on the board 20 bucks

conversion from silver to blackface specs 50 bucks

2-3 hous of labor 100 bucks


Owning an early 70's silverface now blackfaced... Priceless

this sounds like a tv add, doesn't it?

[itbepopples]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

I always wondered...can one replace the SF faceplate with a repro BF faceplate?

[Scott_F]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

Just take a small edge and seperate the glued plate from the chassis. then scrape off all the glue, glue the new one on.

[Jeff Seal]

Re: Speak wisdom to me ol' great tube amp doctors in the house.

A word of caution, the only drawback to older amps is usually the cost of "restoring" the circuits to within specs or better yet "optimizing" a design. Tubes do wear, but the components associated with them do too!

The chances that the components are within specs in this old of an amp, are almost non-existent (although you could get lucky!). I would highly suggest having your local tech, assuming he's worth a flip, go through the entire circuit. It is not uncommon for some of the older amps I get in to require a massive overhaul, depending upon how hard they have been used. Usually this doesn't exceed $250 PLUS tubes, but $200+ tubes is not uncommon.... Although most people look at it as a rather hefty bill, it actually equates to less than 7 dollars a year! Once it's done, you should be set for another 30 yrs +...... Old amps are great when they work right!!!!!...

I would highly suggest considering "blackfacing" it should you get it!

JS