HELP, MY RM4 NEEDS REPAIR !!

[Graham Pearson]

My RM4 was exhibiting identical behavior to this YouTube video:
http://www.youtube.com/watch?v=hlpp2Jwyawc

My RM4?s volume was cutting in and out. If I rotated the RM4?s Master volume control to the max a few times, the volume would come back but then cut out again, sometime a few seconds later, sometimes a minute or two later. Several other folks on this forum have seen the same problem. For example, Mattfig described it this way: ?The tone starts to get all fuzzy and weak?.

It turns out that the contacts in the Series Loop Send jack in my RM4 were dirty. The Send jacks in both the Series and Parallel Loops are part of the forward signal path. If you insert a jack plug in either of these Send jacks, the guitar signal is interrupted and nothing appears at the output. If the ?empty? contacts in either of these jacks are dirty, your signal will either be non-existent or ?fuzzy and weak?.

Here?s a trouble-shooting scheme for isolating a problem with your RM4. This scheme is built from various suggestions in other topics on this site:

1. Try using a different guitar and jack-to-jack input cord.

2. Make sure the problem is independent of which modules are loaded in your RM4. The volume from all 4 modules should be affected in the same way. If not, there?s a problem with one of your modules.

3. Switch the Ground Lift switch on and off.

4. If you are not able to use the RM4?s front panel button to change between modules or you cannot use MIDI to change between modules, the problem is probably on the MIDI board.

5. Try both the front and back input jacks. If one of these doesn?t work, it needs cleaning.

6. Use a jumper cable to connect the Series Loop Send and Return jacks and another to connect the Parallel Loop Send and Return jacks. If this cures the problem, take the lid off and clean the Series and Parallel Loop Send and Return jacks.

7. Swap out all 3 of the RM4?s tubes.

8. Take the lid off and make sure all of the connectors are firmly seated.

9. Check all the fuses and reseat them in their holders.

Prior threads regarding this problem:
http://mtsforum.grailtone.com/viewtopic.php?t=11169
http://mtsforum.grailtone.com/viewtopic.php?t=11355
http://mtsforum.grailtone.com/viewtopic.php?t=12777

 

[Mattfig]

Sounds like a genuine cold solder issue...****...But that's quite a comprehensive set of things you listed...Should be a good resource...

Good luck...If you don't mind keeping us posted that would be cool...These issues are not uncommon 'round here but it seems there's often different solutions to the same symptoms...

 

[Graham Pearson]

I've updated my initial post with a scheme for RM4 trouble-shooting.

 

[kc2eeb]

Make sure the series and parallel loop jacks are functioning properly.
Connect the in and out jacks with a patch cord. If that fixes it then the jack shorting switches need cleaning.
Make sure the volume pot shaft hasn't taken a hit and unseated it's back cover. Pull the knob and see if the pot shaft is stable and not wobbly. If you pull out on it you should feel a small movement out with spring tension on it.
The tension is from the wiper. You should not be able to feel any movement when you push in on the shaft. The pot's back cover holds the shaft in proper
position and tensions the wiper on the trace.

 

[Jaded Faith]

A lot of good advice in here and be sure to try the suggestion on the loop. If you get nowhere we can talk about repairs. The next 5 weeks are going to be insane for me, but after new years it should get better.
Keep me informed and good luck.

 

[bruce egnater]

Sounds like the main level pot is either dirty or just plain broken. You can try cleaning it but you need to do it from the inside by spraying directly into the pot. This cannot be done from the outside. If cleaning doesn't help, replace it.

 

[Graham Pearson]

Many thanks to everyone who responded here. It turns out kc2eeb had the right idea. The Send jack in the Series Loop was dirty and caused the signal to be "fuzzy and weak".

I've updated my initial post with a scheme for RM4 trouble-shooting. I hope this is helpful to other RM4 owners.