Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

What function do these resistors provide?

1/19/2006 1:38 PM
What function do these resistors provide?
I am rebuilding a hacked up Fender bassman and found some resistors in the power supply that I don't understand. Each of the rectifier diodes is paralleled with a 470k resistor.  
Does anyone know what these resistors do for the circuit.  
I drew the schematic up  
1/19/2006 3:16 PM

My guess is that they act to distribute the inverse voltage evenly across the diodes. I have not seen this in other PS designs and I don't know if it is necessary but it probably doesn't hurt.  
Book Of The Day The Ultimate Tone, Volume III by Kevin O'Connor
Have you ever wondered if there is a better way to build a Bassman, Champ, Plexi, an 800, AC-30, Bulldog or Portaflex? Or you wanted to build an SVT with off-the-shelf parts? How about a master-volume amp that doesn’t change tone with the master setting? Everything you need to know is right here, including: proper grounding techniques, wiring methods, and mechanical considerations. Eighteen chapters cover the “iconic” amps everyone knows and loves, with schematics and layouts for each, along with the technical history of the product. Eyelet-board and chassis-mounted tube socket construction is used throughout, for easy servicing and modding. TUT3 is very accessible even if you cannot fully read a schematic and is a "must have" if you are going to build an amp for your self.

Note: The Ampage Archive is an Amazon Associate site. A small commission is paid to the site owner on any qualified purchase made after clicking an associate link such as the one above.
1/19/2006 3:57 PM
Tom Phillips

Each of the rectifier diodes is paralleled with a 470k resistor.  
That was an accepted practice in the early days of solid state rectifiers whenever they were stacked in series to get a higher voltage rating. It was done exactly for the reason DG gave.  
IMHO it is not needed with the rectifier diodes currently available. I never have seen a stock Fender built that way so I would say that someone added them to your amp.  
   Page 1 of 1