TubeMeister 18 Head Effect Loop Not Working on Gain Channel

I have an older Tubmeister 18 head that I bought used. I recently purchased a delay and I am trying to use it in the effects loop. The effect loop will only activate (not sure the correct term to use here) when the clean channel is switched on. It does not work when the gain channel is switched on.

Is this to be expected on the older head or is this something that I can have repaired?

Any thoughts and ideas would be appreciated.

Mike

That's a real odd one there! I can't see any reason why this should happen.

The Effects Loop in the TM18 is a plain old feed through with no additional control switching of the loop such as you get in the bigger models. Turning effects on and off must be done on the pedals once they are plugged in. The signal path is exactly the same for both the Clean and Lead channels, absolutely no difference. The output from the preamp in both channel modes goes through a loop buffer which can be muted internally but that isn't an issue here. It then passes on to the loop's Send socket. As is normal with most amps, the Return socket wafer switch is used to bypass both sockets when nothing is plugged in. When you have a pedal plugged into the socket this wafer switch is opened and the signal is routed back into the Return from the pedal and on to the power amp. That's it! It should be exactly the same for both channels so if one works so should the other.

Are you sure this isn't just a factor with the pedal where the effect is not so obvious with the higher Lead channel signal? Is there really no delay added even when you play very softly and staccato on the Lead channel? Which delay pedal are you using?

bordonbert wrote: Are you sure this isn't just a factor with the pedal where the effect is not so obvious with the higher Lead channel signal?

I tried it in 1, 5, and 18 Watt modes at low volume with gain about 12 on the gain channel and nothing. It works fine on similar settings on the clean channel.
 

bordonbert wrote:Is there really no delay added even when you play very softly and staccato on the Lead channel?

 
Nothing at all.

bordonbert wrote:Which delay pedal are you using?

Mooer Ocean Machine

I will experiment more and If I cannot figure this out I will have an amp tech take a look at it. I will let you know what I find out.

Thanks for your reply,

Mike

Do you have any other pedals to test it with? Any pedal will do, it doesn't matter what effect it gives. You could see if a different pedal shows the same symptoms of working when you are in Clean mode and not doing anything when you are in Lead.

There really is absolutely no mechanism for this to be caused inside the amp.  As I said, the FX loop setup is exactly the same for both channels without any switching action at all when channels are switched.  This surely must be an interaction on the Mooer.

I don't know if this is relevant but have a look here:  Mooer Ocean Problem Report  Have a look at post #254.  It looks like the pedal had problems with cutting out and losing its effects and it may have involved signal levels.  If the channel is changed to Lead it may be that the increased signal level is triggering something like this inside the Mooer.

The software glitch reported on that forum had a firmware update fix made available.  Has your Mooer had this firmware update applied?  Even if you have recently bought it new it may be an older stock item with the old firmware still installed.  Does this seem to be relevant?