Volume failure on mk5

[Pete1340]

Mk5 90, worked fine then next time I used all the volume gone. Can hear each channel but no volume on each. Plugged guitar into fx return and it sounded ok so assume power stage working ok. Tone controls work on each channel, gain seems to be operative but the volume on each channel doesn’t effect the volume of output. No reverb on chan 1 and 2 but on chan 3 it surges up and then levels off. I believe the amp had a service and new reverb tank just before I bought (2weeks ago). About to try swapping valves as I have some out of a triaxis (which is another boogie product bought 1year ago and ld1 Red failed after a week) really not happy now with boogie amps. 2 bought 2 failed. Any advice welcome.

 

[rarebitusa]

Mk5 90, worked fine then next time I used all the volume gone. Can hear each channel but no volume on each. Plugged guitar into fx return and it sounded ok so assume power stage working ok. Tone controls work on each channel, gain seems to be operative but the volume on each channel doesn’t effect the volume of output. No reverb on chan 1 and 2 but on chan 3 it surges up and then levels off. I believe the amp had a service and new reverb tank just before I bought (2weeks ago). About to try swapping valves as I have some out of a triaxis (which is another boogie product bought 1year ago and ld1 Red failed after a week) really not happy now with boogie amps. 2 bought 2 failed. Any advice welcome.

Did you try running it in 'HARD BYPASS/LOOP ACTIVE" mini toggle in the bypass position"?

 

[Pete1340]

Did you try running it in 'HARD BYPASS/LOOP ACTIVE" mini toggle in the bypass position"?

 

[Pete1340]

Hi rarebitusa, thanks for reply. yes tried hard bypass but no sound at all. Checked valves are seated properly etc. amp is 5 years old and not been gigged before I bought. Have contacted Seller and he says there was a service done and a new reverb tank. That’s what is now concerning me ie has the new tank effected something because while there isn’t any volume there is sound. When on chan 1 there’s no volume and no reverb heard chan 2 no volume and no reverb, chan 3 no volume but loads of gain(but quiet) the reverb when switched on does come through but swells in volume and then dies down to same volume as the other channels.Everything was working ok for a week after bought then when I came to use again no volume. Going to try swapping out valves next but not convinced it will improve. Hope that all makes sense.

 

[Eevil]

Hi rarebitusa, thanks for reply. yes tried hard bypass but no sound at all. Checked valves are seated properly etc. amp is 5 years old and not been gigged before I bought. Have contacted Seller and he says there was a service done and a new reverb tank. That’s what is now concerning me ie has the new tank effected something because while there isn’t any volume there is sound. When on chan 1 there’s no volume and no reverb heard chan 2 no volume and no reverb, chan 3 no volume but loads of gain(but quiet) the reverb when switched on does come through but swells in volume and then dies down to same volume as the other channels.Everything was working ok for a week after bought then when I came to use again no volume. Going to try swapping out valves next but not convinced it will improve. Hope that all makes sense.

Is the mute in solo pot pressed in?

 

[rarebitusa]

Ok, just throwing ideas out here. Curious do you have a footswitch? If so perhaps disconnect it and manipulate the controls from the back panel to see if anything changes. The other thing to try is to take the FX loop Send to an outside monitor amp and see what the isolated preamp is doing. I agree it doesn't sound like a tube. The reverb circuit is parallel to the signal path and without a footswitch the reverb is always on. So just turning the reverb levels down to zero should leave the base signal thru the chans and see if anything changes. Also try manipulating the mute push/pull on the solo knob. (Oh never mind @Eevil beat me to it

 

[Pete1340]

Hi, yes but no sound. Tried reseating

Ok, just throwing ideas out here. Curious do you have a footswitch? If so perhaps disconnect it and manipulate the controls from the back panel to see if anything changes. The other thing to try is to take the FX loop Send to an outside monitor amp and see what the isolated preamp is doing. I agree it doesn't sound like a tube. The reverb circuit is parallel to the signal path and without a footswitch the reverb is always on. So just turning the reverb levels down to zero should leave the base signal thru the chans and see if anything changes. Also try manipulating the mute push/pull on the solo knob. (Oh never mind @Eevil beat me to it

Thanks for reply,, yes tried without footswitch but no difference. Will try an output from the send. Tried the mute but no difference when pushed back in. Solo doesn’t do anything amp stays at same volume. Really pxssed off having only bought 2 weeks ago. Worked fine and in absolutely mint condition to look at.

 

[Pete1340]

Is the mute in solo pot pressed in?

Yes mute is pressed in.

 

[rarebitusa]

First I totally get the frustration... new amp and all. Well if I had to guess it seems there is a problem with the muting circuit. I am a bit familiar with the switching control, muting and reverb circuit of the V:90. If misery loves company you have a friend as I recently have lost the reverb on my V:90 as well.

However it is worth rolling the preamp tubes just to see if anything changes.

 

[Pete1340]

The mute switch works and the reverb, while it surges, does work on chan3. Doesn’t work on chan 1+2. Am doing a valve swap ( got a spare new 7025) so will do a swap of each pre amp valves and see what happens. I do get about 1/4 - 1/2 watt of volume using the standard input and the power amp running at full volume. Guitar plugged into effects return also gives decent volume. On all three chans the tone controls work and the gains work just no individual vols working. The solo switch doesn’t do anything and the eq only has an effect on chan3. My guess,I have bought a bad one and completely deflated ( a lot of money out of limited pension and savings) .tried to contact seller but as yet no response.(Suprise)

 

[Pete1340]

Firstly a big thanks to those that responded. Wow!! 1 valve. Valve 3a/3b changed it out today and everything came back to life. Let it run for 5mins and everything stayed on. Still got to put screens back etc so once done will try again and hopefully all will be well (touch wood) Again big thanks to all. Let’s hope not back on here for a while…..

 

[rarebitusa]

Well, that's excellent news. V3 are gain stages for Ch 1 & Ch 2 so at 1st glance perhaps one would think Ch 3 would have shown more function, but as you stated the reverb was different on Ch 3.

BTW, the forum here is also for discussion about Mesas in general Feel free to come back and share thoughts and experiences on your V:90 it's a great amp.

 

[Pete1340]

Well, that's excellent news. V3 are gain stages for Ch 1 & Ch 2 so at 1st glance perhaps one would think Ch 3 would have shown more function, but as you stated the reverb was different on Ch 3.

BTW, the forum here is also for discussion about Mesas in general Feel free to come back and share thoughts and experiences on your V:90 it's a great amp.

Hi rarebitusa, V3a + 3b do find their way around to ch3 master so I guess thats why it’s started working. I can’t really be sure but looking at a schematic there’s deff a connection. Anyway it’s working, so far. Going to try it again later after putting shields and grill back on.
Thanks for help and suggestions…. I always look in on the site. I even sent a donation, these forums can be essential sometimes.
Thanks again, Pete UK

 

[DECEMBER]

Firstly a big thanks to those that responded. Wow!! 1 valve. Valve 3a/3b changed it out today and everything came back to life. Let it run for 5mins and everything stayed on. Still got to put screens back etc so once done will try again and hopefully all will be well (touch wood) Again big thanks to all. Let’s hope not back on here for a while…..

Yeah, always try new tubes first, especially if it was bought used. Tubes can be damaged in transit, and if the amp is being sold, it's likely it hasn't been used in a while. New tubes can solve all kinds of issues with noise and signal/volume loss. And it's a good idea to keep a full set of spares on-hand, because you never know when one will fail.
I like to put all new tubes in as soon as I receive a used amp. This way, I know they're all functional, how old they are, and I get to meet the amp at its peak potential. Then, if there are any issues, you know it's something beyond tubes and the amp needs to be returned, unless you want to spend even more to take it to a tech.