RM100 trouble

[FFFDFEFRFKFFF]

So I've basically had complete and total hell since I got my RM100. I got it used off of these great forums and after a couple of weeks I finally picked up all three modules and was ready for band practice. After blowing a fuse because I had it set to the wrong impedance, it worked for about a half a minute and blew the next fuses and a current screener, I think that is what it is called at least. So after I took it to get it looked at since it wouldn't come on after the second set of fuses and current screener blew. Now, a month and a half later, I get the amp back and bring it an hour and a half drive home and take it to band practice. Getty to get the thing back on since I never really got to give it a good test I plug it in turn it on standby, after checking the tubes and impedance, and go tune my guitar. Upon my return no, I mean nothing at all, sound comes from the speakers. The fan never got on my nerves more. I checked the fuses and two are blown so I change all 7 on the inside and check the main one by the power supply and still no sound. Again I check the fuses under the midi section and they're blown. All of that leads me to the question of does anyone know WTF could cause this?

In case that was too much to read: the fuses under the midi section blow every time I power my amp on, WTF?

 

[Julia]

Tubes. The impedence mismatch probably blew your quad causing it to take out the fuse. Now the question is did you take out the screen grid resistor, too. Now this can cause other things to fail as well. The question is what else got taken out. The tech probably didn't fix it, or didn't do it right.

I had a EL34L start arcing in my Lynch box. It actually caused the fuse to shatter. The tube next to it started to redplate. I shut down the amp and called my tech. He knew I had a pair of matched EL34s from a quad that failed on my old JVM. The pair was still okay. So I put those in the spot where the two bad tubes were. I turned on the amp and watched it closely for 20 minutes. Nothing happened, so this meant that I got lucky (for a change). The fuse protected the screen grid resistor. So then I paired up the EL34s together and the EL34Ls together (inside and outside). Then I rebiased at 33 mV per tube. And ordered a new quad since I don't expect four tubes from two bad quads to last much longer.

I want to get a new quad in ASAP, which means sometime this coming week my =C= EL34s will be here from Magic Parts (Ruby).

 

[FFFDFEFRFKFFF]

Mine was arcing too. I'm an idiot for not changing the tubes sooner. I was planning on ordering them when I got paid so they're on their way already. The screen grid resistor is the white thing, correct? If so it would be good if I checked it and the current went through, right? I'm just really trying to avoid the long trip/wait to take it back to the place that looked at it before. Thanks, for the reply.

 

[jmgman70]

Tubes amps sound great feel great but can be trouble some if your new at them,they take a LOT of maintenance,but tubes are usually the colprit

 

[Julia]

Mark the tubes that blew fuses. Discard those. Keep the ones that didn't blow the fuses... okay now you're set. If the fuses blow with the new tubes, take the amp to a tech. It is beyond user handy-work.

Make sure you have a good digital multi-meter. Get a good one. It's worth it.

* make sure your amp has the proper load setting on the impedance switch to match the impedance of the speaker cabinet. If you don't you could fry your transformer in addition to the tubes.

* If your amp blows a fuse, do not simply replace the fuse and continue. There's a reason the fuse blew. If you have a bad tube indicator light on in the back of this amp, the first thing that should come to mind is to replace the tube.

* take one of your spare tubes and plug it in the spot

* replace that fuse with a 400 mA FAST BLO -- call Randall customer support if you can't find these.

* now before you start playing anything. turn the amp on and watch the back of the amp closely for any strange behavior like tubes redplating or not lighting up at all. Leave the amp on for 20 minutes.

* if you've replaced the fuse and the tube doesn't light, you've got another problem. Contact an amp tech.

* if the tubes look fine after 20 minutes, turn off the amp. Now it's okay to put in your NEW quad. -- yeah you CAN just replace the bad tube, but bad tubes tend to run in batches, so best to do the full quad. Save the ones that didn't fail, mark and discard the ones that failed.

* turn the trim pots on the power tubes counter clockwise about 1/4 turn on the amp. Then turn on the amp and let the tubes warm up for about 15 minutes, and adjust the bias to within specification for that tube per the manual. DO NOT over turn the bias screws. They are very sensitive.

* Use only the tubes specified in the owner's manual. Make sure you have the same types of tubes paired up with each other (i.e. EL34 on the outside, EL34L on the inside if you mix tube types).

* If you do not know what you are doing, take the amp to a tech. Find out who is the authorized Randall service tech in your area, if you haven't already.

* Never gig without a backup. That's my 5150 II. It's a workhorse.

 

[Mailman1971]

I just went thru this very thing. Kept blowing a internal fuse. I am pretty sure it was a pair of EL34's. I had a new set of 6L6's and swapped out the "bad" EL'34s and so far no problem! I am still weary. I FN hate tearing apart that amp!! :evil:
So I have it out the "shell" for a few weeks to make sure. I am sure its fine....but it isnt hurting anything like that for the moment. :wink:

 

[FFFDFEFRFKFFF]

So I changed the tubes, fuses, and biased my RM100. The amp cools down and I bring it on again and wait for it to warm up then I flip off standby and magically there is sound. Then in the middle of uttering "Thank you God," the unthinkable happens...the SAME thing happens again, spark fuses go out and no sound. Frustrated I take it back to the place that worked on it before and nicely asked them to fix it correctly this time so I don't have to come back and yell at someone. I find out something Friday...

 

[Mailman1971]

Mine did it to me back to back as well. Found out it was a pair of bad tubes. I kpet it out of the headshell for a few weeks to make sure. I guess there are some bad EL34's out there and I had a pair! :x
Its been running fine the past month (knock on wood)
But After having that happen a few times really really sucks.......
I have faith though. :roll:
So far so good!! :mrgreen:

 

[FFFDFEFRFKFFF]

I don't know about the thing anymore. I mean if anything else goes wrong with it I'll just have to get rid of all of the MTS gear and go for something else, the Mark V is looking pretty nice after all. I'm just starting to wonder if it could just be a POS head, I mean I've changed all the fuses inside the amp and the tubes and it still goes out.

 

[Mailman1971]

I was thinking the same thing. This is my 5th MTS head and the only one I had problems with. Maybe a bad batch or something. But so far I trouble shooted and it working ok for me now the past few weeks. Just got in from playing it tonight for about a hour at gig level and all went smooth.
In fact....I am REALLY digging it MORE THAN ever these days.
I had some old modules I broke out and been just really seeing how 'weird' I can dial them in. Getting some great tones out that amp lately. :wink:

 

[Julia]

Now if you guys are gigging with these amps, remember they're no different this way than Marshalls. Back in the day of the JCM 800, to get the sound they got out of them everything was dimed. Everything. People are doing the same thing with the JVMs and having a pretty high failure rate.

You know that point where the volume doesn't appear to get that much louder? The beginning of that is power tube saturation. After that it goes into power tube distortion. It sounds great, but you've entered a danger zone. I don't think amps aren't designed for this. I really don't think any amp is. Marshall sold the Power Brake and promoted it for use with their amps, but damn all that thing did was reduce the number of speakers that got blown. The amp failures remained the same or higher. So when you go into that zone you're really cranking out around 200 watts instead of 100 watts. If you're lucky you'll blow a tube and a fuse. If you're not so lucky you'll fry a screen grid resistor. If you're real unlucky you'll be burying your amp in a grave.

EL34s are the worst for this. EL84s second. 6L6s are better, and 5881WXTs are supposed to be even better, but we'll see. The 5881s arrived this morning. The tube makes the EL34 look like a joke just from physical structure. Now this is durability, not tone. I know people who have fried amps back in the day.

I've fried two -- a JVM (under warranty) and a Fender (not under warranty), and almost fried my MTS. I love power tube distortion, but not at this price.

 

[FFFDFEFRFKFFF]

The thing is that I haven't even gotten to run it loud and hard that much except for like ten minutes. Good news though it is fixed, again, and the tech is going to turn it on and demo it for me to make sure it is all fixed and running fine, I can't wait.

I also got a T2 coming in tomorrow from a trade which means I'll have a back up in case the MTS goes down again. I'm going to love having that peace of mind.

 

[Julia]

I took the front panel off my Lynch Box so I can see the tubes. I may just make a plexiglass panel and mount the logo on that. Whoa! then it would be a Randall Plexi!

 

[LoD21]

PS everyone

Don't forget to clean your tubes sockets now and then. Even some of the brand new RM100s are coming with filthy sockets which can cause problems. The boards/sockets sit on the shelves at randall for months collecting dust before they become amps.


Also after talking to the guys at Eurotubes, come to find out that about 50% of the tubes they get in are bad from the start. That's why they test every single one. Other stores will randomly test 1 out of every quad or something like that.

That's how we end up with bad power tubes. Buying from the wrong guys who don't do a good job testing.

 

[Julia]

It's just too bad Eurotubes sells only JJs.

Tubes are subject to "infant mortality". I think my last set of Sovteks did that. Well GC may end up doing serial replacement since those were generic Sovteks. From here on, I'm only buying from Eurotubes (for JJs), Magic Parts Dealers (for Ruby), and Groove Tubes dealers. At least the tubes are tested. Although GT might be going out because of Fender contracting the entire outfit.

Also: http://www.geofex.com/ and http://www.geofex.com/ampdbug/fuseblow.htm

 

[Jeff Hilligan]

As everyone has been stating, its a very good chance it's not the amp.

IT'S THE TUBES!

We have been preaching and only installing Sovtek 5881 WXT's in our Egnater amps. No issues at all. Whenever a customer installs 34's they have problems and voice their frustrations of leaving the modular amp world. That's a shame because it's the selection of tube that causes your dissatisfaction, not the platform. There is no real winner out there in the 34 relm, just stay away from them and your headaches will go away.

 

[Julia]

I just dropped a quad of GT 6L6-GE's in (clear tops). They've been in less than 24 hrs, so it's too soon to know if we'll get past the infant mortality stage, but I really like the sound of them. I've got them biased at 33.5 mV per tube. They seem a little warmer than the 5881WXTs.

Now to find some transparent green plexiglass. A local glass shop will cut and drill the thing for me. I just need to see how transparent it really is first.

My favorite module with them is Mr. Scary ATM -- it is getting into SLO territory.

 

[FFFDFEFRFKFFF]

Jeff no offense but it IS the amp this time. I never put 34's in this amp. I put a brand new set of 6L6's in it and the same thing happened but it is supposedly fixed now, only time will truly tell, and I haven't had any more problems. It sounds too good to give up so if it keeps sounding this nice I might have to just deal with my insecurities about it's unreliability.

 

[Jeff Hilligan]

Jeff no offense but it IS the amp this time. I never put 34's in this amp. I put a brand new set of 6L6's in it and the same thing happened but it is supposedly fixed now, only time will truly tell, and I haven't had any more problems. It sounds too good to give up so if it keeps sounding this nice I might have to just deal with my insecurities about it's unreliability.

No sweat. Sometimes **** breaks.! Glad things are ok now! If you ever need anything don't hesitate to ask!

 

[FFFDFEFRFKFFF]

Actually two of every module modded by Pete, a cab, and a spare head would be great...only dreaming.