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FDP Forum / Amp Mods, Repairs, and Projects / BF Princeton Reverb Rectifier Ampware inconsistency
(This message was last edited by bmarr at 08:32 PM, May 18th, 2012)
(This message was last edited by bmarr at 09:06 AM, May 20th, 2012)
FDP Forum / Amp Mods, Repairs, and Projects / BF Princeton Reverb Rectifier Ampware inconsistency
bmarr
USA
bmarrMay 18th, 2012 06:57 PM Edit Profile Print Topic Search
Topic
I need to replace the rectifier tube on my BF Princeton reverb. In the amp description on ampwares.com it states that the correct tube is the 5AR4, but the attached schematics show 5U4GB. I know these tubes have similar properties, but what is the historically correct tube?
Thanks,
Brian
damuniz
Contributing Member
*****
South Jersey/USA
She turned me into a newt!....May 18th, 2012 07:59 PM Edit Profile Print Topic Search
Topic
More knowledgeable people will be along shortly but I think it would depend what year your Princeton was built.
Do you know what year it is or what circuit it is?
bmarr
USA
bmarrMay 18th, 2012 08:31 PM Edit Profile Print Topic Search
Topic
The transformer says 1966, but I think it is a 1967
Liquid Smoke
USAMay 18th, 2012 09:27 PM Edit Profile Print Topic Search
Topic
I asked the same question regarding a '69 Deluxe Reverb. Scroll down about 12-15 posts for the responses I got. Good luck
anteriorl5
USAMay 19th, 2012 06:01 AM Edit Profile Print Topic Search
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My BFPR takes a 5AR4/GZ34. The way I understand it (and I could be wrong), when Fender started using plastic wire/getting sloppy with lead dress late '69 and on, they used the 5U4. The 5U4, because of its higher internal resistance, drops the voltage (some 50 volts), for more stability. It also draws more heater current, about 50% more than the GZ34, so puts more demand on the power transformer. So with no changes to the bias current, it's a balancing act between stress on the PT running hotter with the 5U4 and higher voltage to the 6V6 power tubes which might short out.
bmarr
USA
bmarrMay 19th, 2012 04:30 PM Edit Profile Print Topic Search
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anterior15 Thanks, that makes sense. The schematics have a couple of dates on them one as late as 1971, so perhaps the schematic is for a silverface but listed as a blackface. The model on the schematize is "Princeton Reverb-Amp B1270" My tube chart says that my amp is an AA764, which appears identical to the AA1164 configuration that uses a GZ34.
SoK66
Contributing Member
****
USA
We had the hit but Van got the moneyMay 20th, 2012 11:27 AM Edit Profile Print Topic Search
Topic
BFPRs are all AA1164. SFPRs are "all the other ones". There atre two AA1164 diagrams, one with GZ34 and one with 5U4GB rectifier. Otherwise identical. Only the earliest PRs used GZ34s, by 66 they were all 5U4s. FWIW, PRs really didn't change substantially until the pull boost models which were phased in starting '76. Even there the changes are minimal.
Steve Dallman
Contributing Member
*****
Merrill, Wisconsin
Ain't turned 60, but I got my blinker onMay 20th, 2012 06:57 PM Edit Profile Print Topic Search
Topic
Fender switched to the 5U4GB because 5AR4/GZ34's became harder to get in the quantities they needed. They raised the voltages of the power transformer to make up for the voltage drop, but the schematics didn't show any voltage changes. If a 5AR4 is put into an amp designed for a 5U4, the voltages will likely be higher than the filter caps are rated for.
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