Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fiftynine on September 02, 2010, 04:03:40 pm
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I've read what Doug thinks on this but wanted some more information.
I'm sold on an earthed mains cable and new bias and filter caps. He says upgrade the 10k power supply resistors, the 470's and 1.5k's on the 6v6's and the plate load resistors (if they're hissing). I'm OK with all that. But he says do the 7 x 25/25 caps on the board. What does everyone think to that? Can I test them reliably in-situ or will they just be passed it?
Also, it's the original US 110 PT and I'm in the UK. I have a big plug in step down transformer to take the voltage down to 110 but wanted something more permanent. I can put a 230v tranny in the amp no worries but wondered how much of the amps vibe would be lost? Can anyone advise?
Has anyone got any other advice?
Thanks.
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If it sounds good and works well then don't touch it.
I would spend the money to build a second one with the new PT. Measure everything, I'm sure those carbon resistors drifted and build an exact duplicate with the new transformer. It should sound pretty close.
Once those amps are gone or changed that's it. If you change the PT chances are that old PT will never go back in there and another original piece of history will be destroyed. To me it's kind of like painting a mustache on the Mona Lisa... :laugh:
Just my opinion. I have seen way too many nice Fender amps hacked thinking oh they will just keep building them, they didn't.
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I would probably change the two prong cord and thats it. I have learned not to alter the vintage amplifiers. Long hard lesson. Many fewer originals around.
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This is a very good question. In a similar vein I have a Brown Princeton 6G2; 2-prong chjord w/ 2-way Ground SW on rear panel: tolex not great; electronically not functioning; AND has 94VAC on the chassis! Obviously a cap job is in order. Hopefully the iron is OK.
How much of this puppy to chop up? Maybe leave the original cap can in place? I guess I could install new filter caps on a board mounted to the PT tranny bolts & thus drill no new holes.
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If you want to get it up and running reliably, you need to do the things that you listed in the original post including the 25/25s.
If you want to maintain history, then don't.
Happy medium......... Do the needed changes, and keep the original parts under lock and key so that it could be restored to original at any time. This also includes the PT.
66 was a CBS year. So, although it is a Blackface, it is not a "Pre-CBS" blackface and therefore not quite the gold nugget that some others might be.
Also, the only way to really keep it original is to shelve it. Because at some point, something is going to fry, burn, die, cook, or otherwise meet its demise and then you will be forced to make it non-original or just have a non-working amp sitting around.
That's my .02 for your consideration.
Dave
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I agree....
With all the parts available these days I really feel there's no reason to even use an amp like that anymore. I built so many that sounded as good or better then the originals. And honestly when you gig nobody knows the difference as long as you get your sound it doesn't matter what you plug into.
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It kind of depends upon whether you yourself wish to keep the amp to keep 1: as a museum piece, or 2: as a working amp.
These amps can fetch over $2K in good esthetic condition. For that money, you can buy 2.7 qty silverface AB763 Deluxe Reverbs that are the same thing. I had a beautiful '65 or '66 Deluxe Reverb that I ended up giving away for free. That was in 1980...they were worth substantially less.
It's hard to give advice like this....I used to be major old guitar hound and bought and sold actively in the 70's & 80's; I never really felt that way about amps (but then, I never particularly liked tweed amps) Now I still like the guitars but they certainly do a lot less for me than they did at one time. I bot a near-new Strat plus and mechanically it simply devastates my '64, '57, and '60 Strats. Butchers them. Pickup wise it utterly sucks but as a playing instrument it kills my older guitars.
These days I'm more inclined to sell them. What's a '65 Jazz Bass Ocean Turqoise (aka Sherwood Green) body & headstock worth?
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I'd sell it and make half a dozen amps with the money. Deluxes are good amps but not sacred. It's a fairly easy amp to duplicate... and then you can fix the shortcomings (subjective and different for each person) without destroying the value.
Dave
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Amen! :angel
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Thanks everyone.
If I left it alone (apart from the mains cable) and used it daily, what is the worst that could happen/blow up/burn out?
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As previously stated, sooner or later something will go south...One big question for me would be: How original is it? If not one thing and I mean anything, has been changed I agree with putting it in a closet or selling it and building a hoffman board based amp. Once something, anything is changed, in my opinion it is not original.. Kind of like the "One owner" items that a dealer is selling. To me, it is not a own owner unless you buy it from the original purchaser....You can't turn around and sell it as a "One owner". Sorry if I digress, I must be getting senile in my old age!!! :grin:
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I'm sold on an earthed mains cable and new bias and filter caps. He says upgrade the 10k power supply resistors, the 470's and 1.5k's on the 6v6's and the plate load resistors (if they're hissing). I'm OK with all that.
Do some reversible, non-intrusive mods. Keep the original parts. You'll need them if you want to maximize resale value.
But he says do the 7 x 25/25 caps on the board. What does everyone think to that? Can I test them reliably in-situ or will they just be passed it?
All electrolytics should be changed.
Also, it's the original US 110 PT and I'm in the UK. I have a big plug in step down transformer to take the voltage down to 110 but wanted something more permanent. I can put a 230v tranny in the amp no worries but wondered how much of the amps vibe would be lost? Can anyone advise?
Changing the PT is OK. Keep the original.
Has anyone got any other advice?
I'd resell the amp, buy a new Hoffman AB763-based DR...
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It's only original once.