Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bibi on August 29, 2018, 10:47:58 am

Title: Fender Tonemaster channel switching Pop!
Post by: bibi on August 29, 2018, 10:47:58 am

Hello,


I am currently working on a Fender Tonemaster amp and it has a problem with the switching relays between the two channels-- namely it pops. 
The circuit as can be seen from the schematic included is minimal at best-- +24V going to the relay and a 4148 diode across.  I have found reports
of this being a problem from the beginning and no wonder!


Is there any known Fender service repair notice for this amp that I haven't found?  I could modify it pretty easily to be an adequate circuit if that is
the best solution.


Thanks for your help!

Title: Re: Fender Tonemaster channel switching Pop!
Post by: VMS on August 29, 2018, 01:55:55 pm

This schematic shows R66 2M2 resistor after the relay and before the PI:


https://el34world.com/charts/Schematics/files/Fender/Fender_tonemaster.pdf (https://el34world.com/charts/Schematics/files/Fender/Fender_tonemaster.pdf)

Title: Re: Fender Tonemaster channel switching Pop!
Post by: tubeswell on August 29, 2018, 02:27:18 pm

Bruce Zinky was eventually fired, so I heard.

Title: Re: Fender Tonemaster channel switching Pop!
Post by: bibi on August 30, 2018, 12:29:53 pm

Well the schematic I posted is a Revision E so that should have addressed some of these issues as it is later than the one on this website. 
Unfortunately, it looks likely I will have to do some modifications to get it halfway decent.