Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pdf64 on October 14, 2022, 07:34:52 am

Title: 6V6 Operating point in Deluxe / Reverb AB763
Post by: pdf64 on October 14, 2022, 07:34:52 am

https://el34world.com/charts/Schematics/files/Fender/Fender_deluxe_reverb_ab763_schematic.pdf
The schematic notes the anodes are 415V, the screen grids will be within a volt of that, and the bias is -35V.
Using the triode connected chart on p4 of https://frank.pocnet.net/sheets/093/6/6V6GT.pdf seems to indicate that a bogie 6V6 would be passing about 33-34mA anode + screen grid current.
Have I got that right?
If so, the resulting 14W idle dissipation seems rather hot, is it better to assume that -
1/ Fender intended such a such hot bias
2/ the readings were taken using weak-ish 6V6 which required a lower than normal bias voltage
3/ measurement  / drafting error
4/ the bias had been set a bit hot accidentally
 :w2:
Thanks  :icon_biggrin:

Title: Re: 6V6 Operating point in Deluxe / Reverb AB763
Post by: sluckey on October 14, 2022, 08:00:35 am

Here are some real world numbers on my DR... 423, -36, 24mA

     http://sluckeyamps.com/tdr/tdr.pdf

Title: Re: 6V6 Operating point in Deluxe / Reverb AB763
Post by: Lectroid on October 14, 2022, 10:56:23 am

Just finished my DR 1-Channel. 

Plates:    412V
Screens: 405V
Bias:      -36V
Ig:         ~25mA

Title: Re: 6V6 Operating point in Deluxe / Reverb AB763
Post by: 66Strat on October 14, 2022, 05:04:38 pm

Tubes in 1963 were considered a consumable that were expected to be periodically replaced. I remember buying tubes at the drug store in the late sixties. There was a tube tester on-site to test your tubes and replacements of common varieties were on hand. It should also be noted that amp manufacturers at that time were trying to get the last watt out of their circuits for advertising propaganda.