Fender hot rod deluxe stuck in drive mode

[gretsch 65]

Assistance requested. Have a Fender hot rod deluxe. Performed twin stack mode and clipped r105. Turned amp on and everything worked great for two minutes. Amp started making a roaring/hissing noise and I started messing with the controls and pushed drive mode button. Amp works in drive but will not change back to clean channel or more drive mode. Footswitch does not change it either. Lost for direction if anybody has any ideas they would be appreciated.

[olddawg]

Assistance requested. Have a Fender hot rod deluxe. Performed twin stack mode and clipped r105. Turned amp on and everything worked great for two minutes. Amp started making a roaring/hissing noise and I started messing with the controls and pushed drive mode button. Amp works in drive but will not change back to clean channel or more drive mode. Footswitch does not change it either. Lost for direction if anybody has any ideas they would be appreciated.

Welcome. Honestly.. “Twin Stack Mod” will probably mean nothing to most of us. I think you should start by returning the amp to the stock configuration. Hopefully you took a picture before your started. Once the amp is back to the original circuit we can troubleshoot using a schematic. Do you have a schematic to post? If not some kind person here can probably locate one. Also it would help to know what kind of test equipment you have and your level of experience? Tube amps can be dangerous, even deadly if you don’t know basic electronics troubleshooting techniques.

[Mick Bailey]

I've come across this mod but different people do it in different ways - if you could explain exactly what you did it may give a clearer picture. The mods themselves may not be the cause, but you could have inadvertently disturbed something else or accidentally bridged adjacent circuits with solder. These amps suffer from a number of 'stock' faults - especially ones that cause switching problems - and before carrying out any modifications need to be checked beforehand. R78, R79, R97 overheat the board and the solder joints break down. Once this happens, any movement of those parts can subsequently cause problems Whenever I'm faced with switching issues with these amps I first establish that the low voltages are present; that is, +/-16v on the opamps and 39vAC on R97. These can be checked with the amp in standby mode - it doesn't need to be operational for the switching to work.

Fender-Hot-Rod-Deluxe-Schematic-1.pdf

[Enzo]

Agree^^^

Once you determine the 15v supplies are present, then use the notes on the left edge of the schematic and the test points throughout the switching circuit to get to the problem.

[g1]

R105 is the resistor to ground at the treble/bass pot junction?
Agree with the others that it should have nothing to do with this and the issue is probably due to the board being moved or parts being wiggled disturbing a solder connection in the low voltage supply.

[gretsch 65]

R105 is the resistor to ground at the treble/bass pot junction?
Agree with the others that it should have nothing to do with this and the issue is probably due to the board being moved or parts being wiggled disturbing a solder connection in the low voltage supply.

I am going to check all these issues and will post back. Thank you

[Tone Meister]

Assistance requested. Have a Fender hot rod deluxe. Performed twin stack mode and clipped r105. Turned amp on and everything worked great for two minutes. Amp started making a roaring/hissing noise and I started messing with the controls and pushed drive mode button. Amp works in drive but will not change back to clean channel or more drive mode. Footswitch does not change it either. Lost for direction if anybody has any ideas they would be appreciated.

Check the channel LED and its solder connection. Easy to get that out of whack when returning the PCB to the chassis.

The "Twin Stack Mod" is a simple mod whereby a jumper is placed between lugs 2 and 3 of the MIDDLE pot. What is does is causes the tone stack to behave like a Twin Reverb - all tone controls OFF = no sound. It also makes the BASS and MIDDLE controls to become interactive. Also, the values of C5 and C6 can be adjusted lower along with the Twin Stack Mod to control the excessive low end in the amp.

[gretsch 65]

Update: Checking voltages on components and bumped the LED and it switched channels from drive to clean. Controls would not change channels nor foot switch but I could bump that LED and it would change back and forth. Re-soldered LED but no change. I ordered another LED.