V:90 Channel Switching Vol Drop Thread

[rarebitusa]

Starting a dedicated thread on this topic since it looks like @spawnofthesith2 has a similar issue as my V:90 currently does.

FWIW this thread topic started here

https://boogieforum.com/threads/mesa-boogie-mark-v-35-footswitch-schematic-pinout.87864/post-544727

The basic problem, upon a channel switch Ch 1 -> Ch2, intermittently the volume will cut out. The channel led goes on and there is still sound but at a very low vol. You can hear an increasing cracking sound and then after a few seconds and it kicks in fully. The problem still occurs but much less often going from Ch 3 -> Ch 2. The FS and related external controls have been ruled out.

Searching the V forum for related issues... found this thread that points to sticky relays, which would make sense in this case.

https://boogieforum.com/threads/mark-v-clean-channel-cutting-out-help.85204/post-524138

Anyway. I'm just starting to dig into the relay controls and which ones are in play when switching. Would like to have an idea of what to poke around for when I open it up and start sniffing around. FWIW I've been deep into the V:90 before and it's a challenging packed beast for sure.

Of course anyone with direct experience troubleshooting Mesa relays or similar problems feel free to weigh in

 

[Eevil]

Starting a dedicated thread on this topic since it looks like @spawnofthesith2 has a similar issue as my V:90 currently does.

FWIW this thread topic started here

https://boogieforum.com/threads/mesa-boogie-mark-v-35-footswitch-schematic-pinout.87864/post-544727

The basic problem, upon a channel switch Ch 1 -> Ch2, intermittently the volume will cut out. The channel led goes on and there is still sound but at a very low vol. You can hear an increasing cracking sound and then after a few seconds and it kicks in fully. The problem still occurs but much less often going from Ch 3 -> Ch 2. The FS and related external controls have been ruled out.

Searching the V forum for related issues... found this thread that points to sticky relays, which would make sense in this case.

https://boogieforum.com/threads/mark-v-clean-channel-cutting-out-help.85204/post-524138

Anyway. I'm just starting to dig into the relay controls and which ones are in play when switching. Would like to have an idea of what to poke around for when I open it up and start sniffing around. FWIW I've been deep into the V:90 before and it's a challenging packed beast for sure.

Of course anyone with direct experience troubleshooting Mesa relays or similar problems feel free to weigh in

Does the fx return work normally while it cuts the signal? (Hard to check)

And whats the state of:
- channel mode
- channel wattages
- tube/diode
- spongy/bold
- solo/normal

this amp has too much going on…

 

[rarebitusa]

Does the fx return work normally while it cuts the signal? (Hard to check)

And whats the state of:
- channel mode
- channel wattages
- tube/diode
- spongy/bold
- solo/normal

this amp has too much going on…

thanks for chiming in

So yes the FX loop appears to be working when in 4CM with the channel switch. The time base effects can be heard even at the initial low cracking volume. The problem occurs with any channel mode or wattage selection. I do recall testing a number of different chan wattage combinations and tube/diode between chans.

But... I have not tested the selections solo/normal or spongy/bold . Also can't remember if I tested with the loop and global master vol disabled. I will try those next.

Yea the relay control on this amp is pretty involved. I will add that the reverb has quit working as well, I don't know when that occurred cause it's not used, could be related.

 

[rarebitusa]

FWIW, I also did test switching to Chan 2 with a signal in to the fx return and there were no vol drops on any of the wattage selections. Then just monitored a signal from Fx Send and it had the problem. Feel it is in the preamp section.

 

[rarebitusa]

Quickly dug thru the preamp section a bit. Most of the preamp relays select between Chan1/2 and Chan 3. Looks like RYC1C is the only relay that differentiates between Ch1/Ch2 and that is for chan master selection. There are are other voicing/mode controls stuff but will ignore them for now.

The muting circuit and the Chan 2 bus are next.