RM4 problem

Hi there everyone, new member and first time poster here..

I've got a problem with my RM4 and I hope someone of you guys can help me identifying the problem.

When I power it in on, everything is as "it should be", lights upp and the fan starts spinning etc.. But after a few seconds all leds light upp (weaker than normal) and there is a drastic drop of volume. There is sound, but it is very low and with lots of unwanted distortion. (The first time i power her upp it takes several seconds before the problem occurs, the second time the problem comes quicker and the third time even quicker etc. The longer the time it's been tuned off the longer it takes for the problem to reveal itself, but never longer than a couple of seconds)

I've tried swapping tubes in the preamp and in at least half of my modules (got 11 stock randall) and tried different modules in different slots, but no result. I tried starting her upp outside of the rack, with no metall in sight (in case of a ground loop problem). My brother opened her upp (he works with electronics, but has absolutely no experience with guitar amplifiers), but he couldn't find anything wrong (no burnt electronics etc).

Next week i'm going to take her to one of the local music shops, but i'm not hopeful of a positive result. When i talked to them about the problem their response were that they would take a look, but they weren't sure if they were going to be of any help (there's severe lack of capable repairmen in town)!

So i'm hoping someone of you experienced guys are able to help me identify the problem. And if someone got the schematics, I would greatly appreciate it!

Thanks in advance.

Btw, thanks for a great forum! I've been reading on and off for several years now, you guys are part of the reason i got into the Randall stuff

Rob at Jaded Faith is your man. He's super helpful with this sort of stuff.
Recently I've got some major issues with my rm100 and I couldn't find the amp schematic for my repair guy anywhere. One email to Rob and within a few hours I had the schematic as well as a few hints for my tech to check.

Just because it seems to be a popular issue, are you using the loops? Have you cleaned the jacks? Just some contact cleaner on a plug in and out of the jacks fixes issues sometimes.

Thanks for the response guys!

Im not using the fx loop, running direct to power amp (peavey classic 60/60) and no fx after the preamp. I've tried using both the pre and post fxloop outputs. I haven't tried cleaning the inputs and outputs, i will give it a try just cause it won't harm doing so. But i doubt thats the problem.

I'll try to contact Rob from jaded faith, hopefully he might have a idea regarding my problem and if he is willing to send the schematics..

Thanks again!

I don't think the loop is your problem (although cleaning this 1-2 times a year is good practice) and it's certainly not a tube issue. The comment about all of your LED's coming on at once and the level dropping is indicative of a problem in your switching circuitry. I'll wager a module was hot-swapped while the unit was on and an arc occurred in the socket. This probably fried something in your switching circuitry.

Your going to need a really good tech to troubleshoot and repair this. It's not going to be a job for the old-school guy who is not used to that type of work. Good luck and let me know if you need further assistance.

Thanks for the reply Rob, much appreciated!

I've sent you a mail..

Hi everyone.. My rm4 preamp is finaly fixed!

Just want to report back to you all regarding my RM4 problem. The problem was a tantalum capacitor that was mounted the wrong way from the factory. . I can't be more specific as i wasn't told much more and i probably wouldn't be able to explain it to you guys either (I'm no tech, and trying to explain and translate something i hardly understand in swedish would probably just confuse everyone)

Thanks everyone (especially Rob) and thanks to Tommy Folkesson (the tech who fixed it) http://tommy-folkesson.nu/

Can't wait to get to play with my randall again!!

I just saw your email and have seen this issue once before. Glad I could help and that you are back in action. Enjoy!