Hi All
Hoping that there might some English speakers here who could help me.

I bought and assembled the Kit Seriel FX-Loop LND150 and then gave it to my amp tech to install in my 1979 JMP 2203 Master Volume 100w Head.

It's not working as expected. Firstly, there is clipping when I use my TC Electronic Flashback delay through it, especially on the low notes. But the main issue is that when I put in an MXR Micro-Amp for a volume boost, there is no boost, just more gain.

I called my tech and he said that he wasn't sure that I would like it, he set the levels in the FX Loop after a lot of time spent trying to balance it between too much gain and not enough. It has been set so that when a patch cable is put in the loop, the volume of the amp is at unity.

My amp tech has offered to take another look at it for me but he is sure it is wired as per the documentation. He does not feel that this is a 'usual' design and is suggesting a Passive FX loop if this doesn't work out.

Hallo,

it would be good to know how and where the loop got installed otherwise it is hard to tell what the problem is. In fact the loop should work fine in a JMP. The TC could be a problem because of the impedance but again, without a schematic and more information it is hard to tell what to do.
You can also send the amp to use for inspection and testing.

Best regards, Dirk

Hi Dirk

Thanks for the reply.

Do these pictures help?

http://s721.photobucket.com/user/odgeuk/library/FX%20Loop%20in%202203?sort=3&page=1

It does seem that the FX loop has been installed correctly between the Master Volume and the Tone Stack (starting with the Treble Control). And another feed taken out to the main JMP board (assume this is the B+).

Please provide a schematic, I won't trace pictures.
If unsure you can send the amp to us and our technic will check it.

Best regards, Dirk

Please provide a schematic, I won't trace pictures.
If unsure you can send the amp to us and our technic will check it.

Best regards, Dirk

Thanks Dirk

I'm not sure I'm able to provide a schematic. All I know is that the FX loop was populated with the components as per instructions, and wired as per instructions (between the Master Volume and Tone Stack). From a wiring perspective, it looks like the instructions have been followed correctly, so I am wondering if perhaps there is a problem with components on the board itself. Not sure how to test if this loop is wired correctly.

I think I shall have to return to my tech to have a look again, to see if there is something perhaps that has been missed in the wiring. Shipping from UK to Germany is not an option I'm afraid.

Any assistance or advice on basic troubleshooting of this loop would be appreciated.

Not sure how to test if this loop is wired correctly.

But your tech should know and I hope he has a scope so he can test if both stages are working correctly or not. If they work correct than the components on the board are ok otherwise not.

Shipping from UK to Germany is not a big issue (yet). You just should make sure that you pack the amp well.

Best regards, Dirk