Trouble shooting help.

[claumi]

Hi,
I use my Mark V with a G-System (4 cable method) and everything works perfectly. I have using it like for the pas 4 years. The other day, I went to practice and decided not to bring the complete rig. So Mark V and guitar is all. I plugged in and started to play. After a couple of minutes, the sound would start cutting out and/or be very low volume. After re-introducing the G-System in the loop everything was fine again. If I remove it and plug directly in the front of the amp the problem reoccurs. Any idea what could be doing this and how to solve it?
Cheers!!

 

[Nicklotsaguitars]

Get a patch lead. Plug it into the send and return on the amp. Without the G system or any other effects. See if the problem continues.Could be a problem on the effects loop bypass.
Also see if it happens when the loop is on or off please.

 

[claumi]

Sounds like a plan. I'll try that and keep you posted.

 

[claumi]

Ok. When I turn off the switch for the effects loop in the back of the amp, everything seems normal. When the switch is in the on position and I'm plugged directly in the front of the amp, the problem comes after the amp has warmed up for about 10-15 minutes. Any ideas?

 

[JLBoogie]

Did you put a cable between send and return on the loop? Just 1 cable, one end in the send the other end in the return.

 

[Nicklotsaguitars]

Could be a bad valve. Could be a million things to be fair.
If you have another preamp valve knocking about the place, it won't hurt to swap it with V4 and if the problem persists v5.
Though were either of those valves bad, you'd likely notice bad performance on channel 3 regardless of whether the effects loop is on or off.
Probably time to get it to a service centre.

 

[Nicklotsaguitars]

Or if it's the Mark V:25 then V5 and you'll notice bad performance on channel 2.

(funny how the manual doesn't list a side of any valve as effects loop send. Only V5 as return)

 

[claumi]

Could be a bad valve. Could be a million things to be fair.
If you have another preamp valve knocking about the place, it won't hurt to swap it with V4 and if the problem persists v5.
Though were either of those valves bad, you'd likely notice bad performance on channel 3 regardless of whether the effects loop is on or off.
Probably time to get it to a service centre.

Up here in Canada it's not that easy to get an amp serviced. Specially when your far from anywhere....Thanks for the tube info I'll try that next and keep you posted.

 

[claumi]

Did you put a cable between send and return on the loop? Just 1 cable, one end in the send the other end in the return.

No will do this next with swtich on and off.

 

[claumi]

Did you put a cable between send and return on the loop? Just 1 cable, one end in the send the other end in the return.

Tried it. Can't replicate the problem now either with or without the cable. Intermittent problem I guess. Will try swaping tubes.

 

[JLBoogie]

No reason to start swapping tubes if the issue is no longer there since you will not know if you got it or not. I don't think you have a tube issue as much as maybe a loop switch sticking that straightened out after putting the jumper in. I would leave it alone and keep a jumper cable close by in case it happened again and be aware of all the conditions that may have caused it. If it keeps happening, call Mesa they are extremely customer friendly.

 

[claumi]

No reason to start swapping tubes if the issue is no longer there since you will not know if you got it or not. I don't think you have a tube issue as much as maybe a loop switch sticking that straightened out after putting the jumper in. I would leave it alone and keep a jumper cable close by in case it happened again and be aware of all the conditions that may have caused it. If it keeps happening, call Mesa they are extremely customer friendly.

I'm not sure I fully understand. The original problem happened when there is nothing plugged into the effect loops and the switch is in the on position and I'm plugged in front of the amp. If i put a cable in the effect loops it'S essentially the same has having the G-System in there, right? When the effect loop is off I have no problem at all. When the effect loops is on with nothing in the loop I start having the problem. Is the loop switch you are talking about on the board or is this the switch in the back of the amp?

 

[Nicklotsaguitars]

It's in the circuit at the back of the amp.
This could be nothing more than a bit of muck in the jack socket. Certainly not worth switching valves round if you can't replicate the problem with the patch cable bridging the loop and the loop switched on.

 

[JLBoogie]

Reading your last post I think you have answered your own question. If the loop switch is on, you need something in the loop even if its a patch cable.

 

[claumi]

The amp should work, as I understand it, with the switch off (bypassing the solo and main volume) or on (including the solo and main volumes) and it does. The thing is that when I use it with the switch in the on position, after some time the sounds begins to cut out or go very low. It will come back to normal if I wait : sometimes yes sometimes no. If the switch is off, I dont experience this problem. I could use it with the switch off, but I would then loose the ability to use the solo boost function and the main volume.

 

[Nicklotsaguitars]

Where is your effects level return knob set?