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Discussion in 'Glowing Bottle Tube Amp Forum' started by d barham, Apr 23, 2019.
is there a good online source?
What brand would you recommend.
I have used "Amplified Parts" or "Antique Electronic Supply". Same place. You can get complete sets for various amps, or mix and match.
I have found J J's to be consistent and reliable. The J J 6V6 is a bit cleaner and a tiny bit louder than others, while the TAD (Tube Amp Doctor) or Genalex are more "vintage" sounding.
Everyone will have their favorites. It's a bit like asking which is the best toothpaste.
Some folks will tell you to only buy "NOS", but it's a crap shoot. Some have scads of money to spend on their hobby. Do you? You may be better off spending some coin on a bias tool to help re-bias the amp with the new power tubes. It's not any more difficult than changing strings, and will yield far better results no matter what brand of tube you buy.
It's doubtful your preamp tubes are gone. The grey plate RCAs in my 78 were still good.
It came with Ruby's which were redplating. Faulty bypass cap on bias circuit. They do matter.
I put some s/h Sylvanias I had which biased up nicely to 14ish watts. They were still in several years later when I sold it.
Not opposed to using non original type tubes. It has Groove Tubes in it now. Don't know that they need replacing. It just seems the amp just doesn't have the juice that it used to. I remember putting some new Sov-Tec tubes in my old bassman several years ago, and the difference it made. Thought it might do the same for the Princeton.
Sorry for being electronically illiterate. I don't know what re-bias means.
If you dont want orig tubes I would
stay away from groove tubes unless you are
looking at them. They rebrand chinese and russian.
Not always a bad thing, but, some better than others.
OK - if this is an original amp and been untouched, it's possible the tubes are worn out. But I have 50 year old preamp tubes that still test 'better than new' and sound great.
The most likely reason the amp sounds like it's tired is it needs the equivalent of a lube and oil change. The amp has electrolytic capacitors inside which are like little batteries filled with acidic gunge. They have a typical life of 20 years. There's one big can that's a bit of a job to change and five or so smaller inside. It's routine for someone who has experience. Couple hours work, lube the control pots, tighten tube spring clinches and check voltages inside, rebias the tubes which means get them operating in the band of safety and good performance.
I just replaced this along with all others in my 1984 Super Champ and it's kicked up everything sonically. It's louder, got more bass and treble and is much clearer. You can see the little bubble of goop squeezing out. It's burst and you can see a little streak of the stuff on the side.
Once they crystalize and dry out, the elements inside can short out - flames and smoke, possibly take out some other components like transformers.
Or they can corrode the case like old batteries or pop the end open and spew their guts out like streamers, made of acidic Araldite. Really nasty to clean off.
Find yourself a good amp tech, get him to give it a good once-over. $200 and it'll be good for another 20 years. You'll be amazed at the difference. It'll be like two blankets have been lifted off it. Silverface amps are very easy to service and made of really tough stuff - if you keep service up to them they are pretty well immortal.
It's also possible if you have the original speaker it's tired. You may like to store it for resale and fit a modern replacement.
The amp should be seen by a qualified tech. Virtually every 70's Princeton Reverb I've gotten in for service still had the original filter capacitor can in place - which is WAY beyond its service life! That can not only cause weak sound, but if a section blows - which can happen with NO warning - you can lose your power transformer along with it.
I wouldn't take any chances with it - get it to a qualified tech, have it checked, and if the filter cap can is original (or over 15 years old) have it replaced and a general checkup done.
This is normal tube amp service - they ALL need it every 15-20 years. It's like changing oil in a car.