RM4 Problems...

[shredzilla]

So I power up my newly aquired RM4 and I notice that the LEDs on all 4 modules remain on at all times no matter if i try to switch channels via the footswitch or via front panel switch

Also I get extremely low output. I have to dime the module leve and the master and its still barely audible. Seems like if I have the level on only one module up, the prgressively increase the level of each of the other modules, the overall volume will increase, but still barely audible.

I tried the obvious things: power reset, different modules, slots, cables, power amps, front input/rear input, different outputs, etc. Possibly a short somewhere ??????

 

[Jaded Faith]

Just woke up and haven't had coffee yet, so I am going easy on the repair advice right now....

My first instincts tell me there is a problem on the MIDI board due to the "all modules on" part. Off the top of my head I can't think of everything that's suspect on there, but I'll try to get back to you on that today. One thought is a bad optoisolstor on the MIDI board. Randall did have a few issues with that part according to Bruce.

I am sure the low level ties into that, but checking the tubes on the amp with known good ones is always a troubleshooting step for those types of problems. Check that and post back.

Rob

 

[shredzilla]

Yeh, swapped the tubes out, no change. Still FUBAR'd.

 

[Disciple]

Any update on this - any suggestions or possible solutions? I just got an RM4 in on a trade this afternoon and have this same issue with it all 4 slot LEDs on at once can't get single with standard switching button on rm4 or via my gcp.

 

[disk11]

Maybe it'll help my problem, where only one slot has the LED on, but the others work fine for now.

 

[Disciple]

Well I troubleshot the midi board on the rm4 with my working rm4 and voila the channels are switching, so looks like previous owner or someone from the store since it was from a music store that closed down...more than likely plugged in or out a midi footswitch with the power on without powering it down first.

Anyone know how to repair this midi board to work again? Maybe Bruce is reading this and can chime in. Nothing looks burnt or charred on the midi board, but something's not right that's for sure

 

[GtrGeorge!]

Ignore this if I am off base..but, (have a tech do this..)
if its a board...pull the board, spray the contacts of it with contact cleaner and and re seat it.
wait 5 min and power it up.

could be poorly seated

GtrGeorge

 

[m0jo]

This is probably not a contacts problem. The fuse is obiously not the problem (then it wouldn't work at all).

The optoisolator could be the problem, we had similar weirdness with an RM100 over here. So your options are to replace the midi board ($100 or free depending on how lucky you are with Randall customer service) or to replace the optoisolator.

The part we needed was PC900V, but check your board to see if that is correct! The optoisolator is pretty sucky to replace (small part on a cramped board), but it's not too hard to do if you have a little soldering experience.

 

[disk11]

Is it the 6 legged IC? Mine says H11L1 503Q. A quick browse through digikey and mouser show several optoisolator ICs that match the first group but I can't find one that match the second group.

 

[m0jo]

Is it the 6 legged IC? Mine says H11L1 503Q. A quick browse through digikey and mouser show several optoisolator ICs that match the first group but I can't find one that match the second group.

The chip on the right is the one I mean, if this is a H11L1 for yours you'll need to replace it with that. I don't know the significance of the second group..

 

[disk11]

Anyone got any more info before I get in touch with Randall?

 

[Mattfig]

Did you get yours fixed Disciple?

 

[Disciple]

Not fixed yet - called Randall and have a midi board coming hopefully to fix problem.

 

[disk11]

Heard back from Randall today, they want to sell me a new board for $125. I hope someone on here knows which optisolater I need to buy.

 

[disk11]

Huge props to Jaded Faith, he told me that these work in modules and RM4s: http://www.mouser.com/Search/ProductDetail.aspx?qs=P36CEcFBmYxn5ViwkIckpw%3d%3d

He also said the H11L1 was the important part, and the stuff after it is just manufacturing codes.