Raytheon 5Y3…OK to use in a Princeton Reverb?

dobbs

Member
Messages
102
I know that the original rectifier is the GZ-34. I wanted to check out how the amp performs with the 5Y3, however I read somewhere that without the standby switch, the 5Y3, unlike the GZ-34, would slam the power tubes with full voltage and eventually cause earlier wear. Should I be concerned?
 

zenas

Member
Messages
8,858
Well sure on paper that may be true but the fact is they made all kinds of tube stuff with 5y3s and just an on off switch including a slew of vintage amps.
I wouldn't be a bit concerned myself. (keep an eye on the bias though)
 

pdf64

Member
Messages
7,755
I would be more concerned about the can cap, as there is likely to be a few seconds after switch on when the 5Y3 is fully operational but other tubes are not yet conducting. That may cause the voltage on the B+ caps to rise higher than would be the case previously.
How old is the can cap?
Pete
 

Oatie

Member
Messages
2,187
I would not use a 5Y3GT in a GZ34 amp,
no-way, no-how.

A 5U4GB maybe, but not a 5Y3GT.
 

zenas

Member
Messages
8,858
A 5u4 draws 3 amps of filiment current. Not a good idea putting those in amps built for 2 amp rectifiers like the 5y3s and GZ34s.
The last amp you want to add more current draw on is a blackface Princeton that came with a GZ34. Rember they have Champ power transformers.
 

Trout

Member
Messages
7,550
A 5u4 draws 3 amps of filiment current. Not a good idea putting those in amps built for 2 amp rectifiers like the 5y3s and GZ34s.
The last amp you want to add more current draw on is a blackface Princeton that came with a GZ34. Rember they have Champ power transformers.

Champ transformers?

According to the schematics,

Blackface Princeton reverb AA1164 uses a 5U4 1964 - 1967

Silverface Princetone reverb (70s) 1968-1981
AB868, AB1270
GZ34 (early) or 5U4GB (70s)

Using/trying a 5Y3 in place of the GZ34 is a non-issue, remember, the 5U4 has an entirely difference warmup spec than the GZ34.

Tube rectifers are not instant on devices, they all require warm up, some are just slower than others. The GZ34 will provide the highest B+ voltage of the three.
 

zenas

Member
Messages
8,858
The blackface AA764 Princeton Reverb came with the GZ34.
I have one of those never seen a schematic for one though.
This is from the Fender Amp Feild Guide.
Thay say 66-67ish but mine dates late 64 and as an early one it came without the logo on the grill.

"Several people have reported having later (66-67ish) BF Princeton Reverbs that indicate AA764 on the tube chart. It's possible this was a typo on the tube chart since there appears to be no AA764 schematic and the AA1164 was a later revision"
 

Trout

Member
Messages
7,550
The blackface AA764 Princeton Reverb came with the GZ34.
I have one of those never seen a schematic for one though.
This is from the Fender Amp Feild Guide.
Thay say 66-67ish but mine dates late 64 and as an early one it came without the logo on the grill.

"Several people have reported having later (66-67ish) BF Princeton Reverbs that indicate AA764 on the tube chart. It's possible this was a typo on the tube chart since there appears to be no AA764 schematic and the AA1164 was a later revision"
VERY rare amp BTW,,, kind of a mystery amp.

Someone posted some info on those on youtube.
http://youtu.be/0f8OiTrnnUA
Schematic
http://www.blueglow.de/images/PRAA764.gif

Agreed on the power trans though,,, that particularly rare model has a champ rated PT
 

pdf64

Member
Messages
7,755
As the can cap is fairly recent then I don't have any concerns about putting a 5Y3 in there; the rise in voltage will only be momentary (eg about 30 seconds), after switch on, until the other tubes catch up with the 5Y3.
Another option is the 5R4, which has similar output performance as a 5U4 but only 2 amps heater current (same as GZ34, 5Y3 etc).
Pete
 

zenas

Member
Messages
8,858
Thanks Trout ! Wierd that mines an early one when the other AA764s are latter blackeface era. Mine even had an Astron cap can.

Also the PTs on the schmatics AA763 is 330/330 where as the AA1164 is 340/340 volts.
 

Tone Meister

Member
Messages
3,266
I have a November '65 PR with an AA764 tube chart that calls for a GZ34. However, the plate voltages are correct with a 5U4GB. That could be a function of modern day wall voltage, but the 5U4 puts things where they should be in this amp. Mine has the stock Mallory cap can.


The blackface AA764 Princeton Reverb came with the GZ34.
I have one of those never seen a schematic for one though.
This is from the Fender Amp Feild Guide.
Thay say 66-67ish but mine dates late 64 and as an early one it came without the logo on the grill.

"Several people have reported having later (66-67ish) BF Princeton Reverbs that indicate AA764 on the tube chart. It's possible this was a typo on the tube chart since there appears to be no AA764 schematic and the AA1164 was a later revision"
 

dobbs

Member
Messages
102
Mine is also a Nov 65 (OK). Not a techie, but I borrowed a bias-meter awhile back and with the original Mullard GZ34, the plate volts on both tubes measured around 420-430. I played out the PR last night with the 5Y3GT. Only when another player plugged his Les Paul in did I noticed a touch more break-up. I play stratocasters and could hardly notice a difference. I wonder if the 5Y3GT runs cooler.
 




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