High B+ GZ34 deluxe reverb

[7xa12]

I did not change the GZ34, and I did not expect so high voltage drop, with limiter and everything connected (of course without guitar )
i will plug in the bias tester tomorrow.
is the -42 V on grid2 ok?
thanks

[Jazz P Bass]

Get rid of the limiter.
It has served it's purpose by showing that there are no shorts.

[7xa12]

Thanks jazz P.
all tubes, speaker, and reverb tank connected ( with no limiter) voltage readings depends on my wall voltage 233- 240v at the time:
Power Tube V8.
Plate 440-457V
Screen grid 443-454V
Control grid -53V

Preamp tubes plate (pin 1)
V1 -205V
V2 -204
V3 - 447V
V4 - 210V
V5 440V
V6 217V

[7xa12]

[barfoden]

Bruce is right on the money as always.... It is only valid to see what the B+ is with all tubes installed and the power tubes biased to 50-70% of max dissipation.

The Reissue deluxe reverb runs at ~ 393V plate instead of the vintage value of 415V. I think this is to prevent customers from burning up the screens of some more fragile 6v6 tubes when they bias the amp hot (70%).

Interesting is that the princeton reverb reissue runs at 435-440V plate at 23mA dissipation at idle. This is relatively hot for a pair of 6v6gt tubes (72% of max), but the princeton power transformer is loaded rather heavily with the 2 6v6 tubes and 4 preamp tubes for its size and the high voltage line is only rated at 70mA so as soon as you bias the 6v6 tubes hotter the voltage drops quickly. The princeton also has a bit more screen resistance with the 1K screen dropper whereas the deluxe reverb has a low resistance choke. Both reissues have 470 ohm screen resistors.

Many modern smaller power transformers will drop voltage rather quickly when loaded down, and the filament line and high voltage line are less independent. If the filament line is rated to 4A at 6.3V and you load it with 2A the filament voltage might give you a higher value than the 6.3V. It should never go above 6.9V with the tubes installed.

I would check your filament voltage with the tubes installed as I have heard others report that hammond runs the filament line rather high.

I have an amp with 3 12ax7 and 2 EL84. This is around 2.5A of filament draw. Pulling the first two preamps tube results in a draw of 1.9A. The small PT runs much cooler and the high voltage line have more current available.

[Ted]

Just checked my notes. The last couple of 60s Deluxe Reverbs I've seen had plate voltages of 433V and 414 V. Our local mains is usually around 235V.

Edit: Going back a little further I found one with 449V