Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: newguitarsmell on January 27, 2019, 10:08:06 pm

Title: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: newguitarsmell on January 27, 2019, 10:08:06 pm

Schematic

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: newguitarsmell on January 27, 2019, 10:10:24 pm

Rest of the schematics

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: sluckey on January 27, 2019, 10:40:29 pm

Instructions are on the schematic.

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: newguitarsmell on January 28, 2019, 01:06:22 am

Now I see it!
Thanks SLUCKEY!!
Now to find it on the TZ board...

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: newguitarsmell on January 30, 2019, 12:39:29 pm

I have looked and looked and see no bias pot.. Can anyone else find it on the schematic and let me know? Why would Fender make you remove auxiliary boards to rebias an amp?  :cussing:

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: sluckey on January 30, 2019, 01:16:44 pm

Bias instructions... page 6 location A3
Bias schematic... page 2 location A1
Bias pot location... page 5 location C3

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: shooter on January 30, 2019, 01:43:07 pm

Quote

page 6 location A3

sometimes I miss the days when everybody talked like this   :laugh:

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: sluckey on January 30, 2019, 02:05:23 pm

Let's see how many get it! :wink:

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: Willabe on January 31, 2019, 08:54:57 pm

Quote from: newguitarsmell on January 30, 2019, 12:39:29 pm

I have looked and looked and see no bias pot.. Can anyone else find it on the schematic and let me know?

Why would Fender make you remove auxiliary boards to rebias an amp?  :cussing:

Don't feel bad, I can't see the schematics clearly. If I enlarge them they get fuzzy. 

It's might be/probably is a type of pot that has no shaft coming out of it, made for PC boards.

You'll find it. 

I think it's by TP7 on page 5? 

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: newguitarsmell on February 04, 2019, 10:12:53 pm

I found it - biased the amp and it sounds fantastic! Thanks all!

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: beeba on April 29, 2020, 09:41:46 am

Hello,
i can't see correctly what is noticed for the bias instructions ...
Do you have schématics with greater definition ?
I can't read the value of R43 on power supply board too ...1K ohms 3w ?
Thank you
regards

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: pdf64 on April 29, 2020, 09:58:46 am

Have you tried clicking on the thumbnail?
Whatever, set to achieve 40mV at TP39.
Pedantic sematicists be warned; the phrase ‘bias current’ is used, shame on you, Fender  :cussing:

Title: Re: Biasing a Fender Princeton Recording Amp - Ideas?
Post by: sluckey on April 29, 2020, 10:39:42 am

Quote from: beeba on April 29, 2020, 09:41:46 am

I can't read the value of R43 on power supply board too ...1K ohms 3w ?

Schematic says FP1K 1W