Mesa Nomad reverb problem

[Amplitude]

Greetings all,

I have a Nomad 100 amp that I like, but I am unable to switch off the reverb with the footswitch. I have reverb in all 3 channels. I can toggle between all three channels using the footswitch and I'm also able to turn on and off the solo boost and eq. When I step on the reverb switch, the LED turns on and off, but there is no impact on turning on or off the audible reverb. When I unplug the footswitch from the amp, the reverb is still present. The reverb volume pots on the back panel work as designed to vary the reverb volume in each channel. However, the problem still exists that I'm not able to turn off the reverb on any channel using the footswitch.

So far, I have:

1) replaced the stock 7-pin DIN cable with a new cable.
2) replaced the J175 FET in the reverb circuit. I have confirmed that there is voltage getting to that FET.
3) replaced the 5532 IC in the reverb circuit and confirmed voltages.
4) confirmed the values of all components in the reverb circuit and traced out the continuity of all components in the reverb circuit.
5) confirmed the continuity from the 7-pin jack to the reverb circuit.
6) cleaned both 7-pin jacks (on amp and footswitch) with contact cleaner.

Just scratching my head at the moment trying to solve this problem and am looking for other ideas to test out.

Let me know if you have any ideas. I'm sure I've missed something simple and basic.

Thanks.
A

 

[user 41014]

I really don't have a clue, but is there a TS jack for just the reverb to test if that switching works?

 

[Amplitude]

I believe the only means of switching the reverb is via the footswitch.

 

[John Micka]

Hi, the Nomad uses those relays on the board for switching doesn't it? Need to check a schematic. Looks like cap resistor fet or IC. Or Zener diode?

 

[Amplitude]

Hi, the Nomad uses those relays on the board for switching doesn't it? Need to check a schematic. Looks like cap resistor fet or IC. Or Zener diode?

Thanks for your response! There are plenty of relays in that amp, but as I understand the schematic, their purpose in the reverb circuit is to switch the reverb effect between channels 1, 2 or 3. As it stands now, reverb is already present in all three channels. What I'm attempting to do is to turn off the reverb and as far as I can tell, I don't see any relay in that schematic that switches off the reverb. I have replaced the IC and FET in the reverb circuit between the footswitch and the 5532 IC. I've also tested and confirmed the other components in that part of the circuit.

 

[bgh]

You probably already know this. But ... my Nomad manual says the footswitch will turn reverb on/off for all channels, but with one caveat:

NOTE: When the Reverb Footswitch is used to disengage the Re-
verb, a small amount of wet signal can still be heard. To completely
remove the Reverb from the circuit, turn the REVERB Control ( of the
respective channel ) all the way off.

 

[Ucci]

It must be so small amount that it is NOT noticible on my Nomad 45 wide head

 

[bgh]

Yeah. I haven't noticed it on mine. I posted about it hoping someone would see it and say something like "Oh yeah. it's true when ____" - and the scenario would match the OP's.

 

[Ucci]

I do know that chnl 3 reverb is almost non existent chnl 1&2 is good and that was direct from Factory tech. he also said to try changing the tube that drives the reverb i forget which one off top of head

 

[ficelles]

I do know that chnl 3 reverb is almost non existent chnl 1&2 is good and that was direct from Factory tech. he also said to try changing the tube that drives the reverb i forget which one off top of head

None of the tubes drive the reverb, it's handled by a NE5532 op amp. The on/off is handled by the footswitch logic circuit.

My Nomad 45 reverb annoyingly distorts in channel 1, although very quietly and only on sustained low strings. Channels 2 & 3 are fine but they have their own shared signal path to reverb anyway.

 

[ficelles]

Fixed my reverb distortion with a new NE5532