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Post subject: Replacement Tubes for Vintage Amp
Posted: Sat Mar 07, 2015 7:33 pm
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I have a 1973 silverface princeton reverb I purchased recently and had some work done on it which included replacing the 6v6’s. It sounds great but the tremolo seems a little weak now. I am considering replacing the other 12ax7’s and the 12at7 also. Good idea or not. Since I changed the 6v6’s I thought it may be a good idea to start over with fresh tubes. Should I replace the rectifier (5U4GB) also? I replaced a worn out 1993 eminence speaker with a new 10a125 weber 20 watt with no dope. Sounds great. Any suggestions would be appreciated.

Joe in Mobile, AL


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Post subject: Re: Replacement Tubes for Vintage Amp
Posted: Sat Mar 07, 2015 7:52 pm
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When was the last time the main filter cap can was changed? If it's been over 20 years --- this may need to be done, the get the cleanest voltage to each section of the amp.

Are the remaining tubes, the same age? I usually replace the rectifier, if it's the same age as the output tubes. They last about the same length of time (in general). I recommend getting a good US made NOS 5U4GB. Any US brand is very good. Black plates seems to be the tube-of-choice. You should check the 6V6GT's idle bias, whenever you change the output or rectifier tube(s).

http://www.ebay.com/sch/i.html?_from=R4 ... =&_sacat=0


A new 12AX7 may help that tremolo, too. The PR's 12AT7 is in the reverb section. I like the new issue Gold Lion B759/ECC83. The JJ 12AX7 is also a nice new issue tube. JJ being a bit warmer tone than the GL, closer to original British Mullard. GL more like the old RCA 12AX7.


http://www.amazon.com/Genalex-Gold-Lion ... B00CEOPL36


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Post subject: Re: Replacement Tubes for Vintage Amp
Posted: Sat Mar 07, 2015 7:58 pm
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The tubes seem to be the same age.

Joe in Mobile, AL


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Post subject: Re: Replacement Tubes for Vintage Amp
Posted: Mon Mar 09, 2015 1:58 am
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You can use modern rectifier tubes too , cheaper than NOS .
That is what I use .

First , do you need one ?


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Post subject: Re: Replacement Tubes for Vintage Amp
Posted: Mon Mar 09, 2015 6:35 am
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Stratele, I've have some not-so-good experiences with modern 5U4GB's. Esp JJ's. Which brand are you using?

If you check the Net... you can find very good US made NOS 5U4GB for $25 or less. These can last as long as 10-20 years. Sometimes more, depending on use. As long as the PSU caps are good --- most US 5U4GB will slowly die. Not short-out or do some such spectacular death event, that I've seen with certain modern rectifiers.




To mods: Can we combine the two parallel threads?


Mucho gracias!


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Post subject: Re: Replacement Tubes for Vintage Amp
Posted: Mon Mar 09, 2015 6:47 am
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I did not have to replace a 5U4 in amp since many years and I did not remember wich modern brand I bought las time .

I remember I put some JJ's GZ34 and Sovtek to replace old 5AR4, never had any problem .


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Post subject: Re: Replacement Tubes for Vintage Amp
Posted: Mon Mar 09, 2015 6:59 am
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Modern 5AR4's have come a long ways, since the 1990's. Esp Chinese made variety. But, the 5U4GB seems to have lagged a bit.


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