jvm410h volume control on od1 and od2 issues

[wyomingrocks]

Hello group, I am having a problem with my JVM410h. Clean channel all three modes and crunch channel all three modes work perfectly.

OD1 and OD2 are a different story, they appear to be stuck in a very low volume mode, you can still higher and lower the mastetr volume but you can only get a small % of the volume you are supposed to get. All other controls work normal.

The only things that don't work are od1 and od2 individual volume controls. I am in the middle of moving right now so all I can do is get an idea from the schematic. I posted it below and it opens in the form of a pdf file. The schematic that has caught my attention is the front panel schematic labeled jvm410-61-02-iss1-1. At the top left is the volume control. The first thing I would like to do is check R219 but I am wondering how to check the relay RL204b, is there a way to check it with out pulling it out of the circuit? Is there another place you would start your search?


http://forum.metroamp.com/download/f...65818165be8d6c

Thanks alot for any help.

[wyomingrocks]

second look

Looking at my problem again I believe I am looking in the wrong area. My bass, treble and mids still are working so the problems I described above would affect those areas as well I would believe. It is "just the two independent channel volume controls that are effected. Any suggestions??? The schematic found here
MetroAmp.com Forum • View topic - JVM schematics

labeled jvm410-60-02-iss2-1

It will open as a pdf when you click on it. On the upper right of the page is where A which is located at the connector of the first schematic goes I believe.

I don't know, I am sort of grasping at the moment, all that is going through my head is something in common with only the od1 and od2 volume controls?

Goodnight and thanks for any suggestions

[wyomingrocks]

one more note

Another thing should add is that I swapped out all preamp tubes for known good ones and it did nothing.

[Enzo]

Dammit, my system locked up trying to post a nicely written response here.

There is only one path through this amp, the od channels switch in the extra two gain stages as needed - half of V6 and V7. The amp works except when they are switched in. Personally I'd be checking those stages for function. Volume controls can't do much if they don't get a signal in the first place.

R219 is a 4.7 MEG resistor. I don;t know how it could be the problem. It won;t be shorted very likely. if you want to test the relay, apply signal to the amp, verify it is at point A on CON8 and then is it also on the non grounded end of R219.

[wyomingrocks]

Thank you Enzo

Thank you for your feedback Enzo, I just wanted to get a good idea where to focus my attention before I open it up. I am working on selling my home at the moment and it will probably be a few weeks before I open it up. Mean time I will be looking at the schematic and the specific areas you mention. As usual your my amp repair hero and I really appreciate your help.

Thanks