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Post subject: '62 Princeton question
Posted: Thu Jun 10, 2010 5:41 am
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I bought a '62 Brown Princeton awhile back and after a look inside it seems that most everything is original.I put a new Weber speaker in it and improved the sound but the tone is not what it could be.The sound is best described as a wah tone with the treble backed off some...that muffled hollow sound in the highs.
I'm going to try to improve the tone but don't want to replace anything that doesn't need it....I know how to work safely inside my amps with the voltage and all but haven't changed the caps to mess with tone before.
What would you start with?


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Posted: Thu Jun 10, 2010 6:32 am
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What is your model schematic. It's like 6G2 or 5C2... ? Easier to help you.
One or 2 6V6 ?
It think it is a 6G2 with 2 6V6's

1-You have to be sure all tubes are good.
2-Be sure if bias is good for the 6V6's. Very important.

In my opinion if you do that well you should have a good tone


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Posted: Thu Jun 10, 2010 7:31 am
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Sorry...it's the 6G2.
I replaced the tubes with some NOS RCAs I had...everything has helped to an extent but it should be better.


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Posted: Thu Jun 10, 2010 7:46 am
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You did not answer if you check and ajust bias to your NOS 6V6.

Are you sure that your NOS 6V6 are better (good) than your old ones ?
I had a Fender Champ to fix last year. It had a good old 6V6, but the tone was better with a new Electro-Harmonix. I did not said that is your case but fix an amp it not so easey.
Do you check the 12AX7 ? the 5Y3 ?

For your safely you should replace the power cord with a 3 prongs


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Posted: Thu Jun 10, 2010 8:25 am
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The RCA blackplate 6v6 tubes are a pair I matched....as good as it gets in my opinion.There is no bias adjustment pot that I've seen,it would be a different method to bias. The other tubes are fine.
I replaced the cord with a 3 prong cord.


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Posted: Thu Jun 10, 2010 10:33 am
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You are right ; there is no ajust bias pot . You should change a resistor ( the 30 Kohms) to have the proper bias voltage.

It could be your soution to better tone and a long life tubes ; a properly bias tubes.

If you never do that before, better find a good tech


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Posted: Thu Jun 10, 2010 12:13 pm
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You may in fact have a problem but be aware -- the brownface-era amps do sound "darker" than the later blackface and silverface models since their tone-stack architecture is cathode-follower based (like the earlier tweeds). The "browns" tend to produce a fatter sound throughout the mids, with less of the characteristic Fender "bite" at the top end.

HTH

Arjay


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Posted: Thu Jun 10, 2010 2:04 pm
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Hey Retro,yeah I had wondered about that and it's been a very long time since I played through a true tweed,my first amp being a tweed Champ,and this brown isn't much different.This amp doesn't have the sparkle that my BF amps do,still I might try a change in a cap to see what happens...I will have to think on it for awhile,since everything seems original.The only thing that had been changed was a wire was jumped from the input to the tremo input to have it on all the time...I fixed that.


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Posted: Thu Jun 10, 2010 2:15 pm
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It's also possible that there's been enough "component drift" within the amp due to age that some of the tone is being strangled out of the signal chain. It might be necessary to statically check each cap and resistor on the eyelet board to ascertain if one or more of them are severely out of tolerance. Best of luck -- these "chases" usually take the patience of a King Solomon.

HTH

Arjay


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Posted: Thu Jun 10, 2010 4:17 pm
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+1 Retroverbial


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Posted: Thu Jun 10, 2010 6:23 pm
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Neat amp man, and great advice from the guys. I would consider replacing the three section cap can, with the highest quality one you can find(and the 25uf/50 on the bias board, per Arjay's usual suggestion). If you haven't already done it, I'd give the amp a really good cleaning. Then I'd do a real thorough voltage test, and per Stratele a bias check. If all is good, I'd consider nice Nos pre amp tubes( Telefunken, Amperex, etc). Only after all that, would I consider a cap mod. Because I think that will yield the least tonal change in the hiearchy of amp components. If this is all a bunch of stuff you've already done or know, my bad. Art

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Posted: Thu Jun 10, 2010 7:44 pm
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Glad you came along, Art......I was running out of suggestions!

:mrgreen:

Antique Electronic Supply has a near drop-in replacement for the can cap to keep the chassis looking period-correct. Mouser may have one as well. I really hate to see those hack jobs where a bunch of electrolytics are stuffed inside the chassis willy-nilly. 6G2's are such neat little amps.

Arjay


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Posted: Fri Jun 11, 2010 5:18 am
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Thanks guys,I love tinkering with these amps and learning more,this is a cool little amp and I just feel there's more to the tone than I'm getting but we will see.
Thanks for the suggestion on the cap can because I want something that looks good too.
Art,all I have changed so far is the tubes and upgraded the cord to a 3 prong,so that's why I wanted suggestions from y'all before I changed something that would alter the sound....after all that's why we love these amps isn't it....I hate to see guys get a vintage amp and start changing everything and anything,you get a totally altered sound.
Thanks y'all.


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Posted: Mon Jun 14, 2010 8:39 am
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I was looking at the filtercap can without pulling the chassis and it's marked 20/20/20 and if I looked at the schematic right it calls for a 30/30/30 multicap....is that right guys?
I have just glanced at Antique Electronic supply caps...so I'm going to check that out again and see what's available.


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Posted: Mon Jun 14, 2010 9:08 am
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The 20/20/20 can caps would be correct for an AA964 blackface but the 6G2 circuit definitely shows a 30/30/30. That said, I don't think it'll make much of a difference in either case so long as you maintain a 450VDC spec.

It's possible that sometime in your amp's past, the cap can was replaced with a 20/20/20.

Be advised, the replacement can caps from AES are slightly shorter than the original Mallory's by approximately one inch. The diameter remains the same and you shouldn't experience any problems lining up the mounting screws.

HTH

Arjay

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