HELP: No sound coming from Rm100

[blasure82]

Last Friday we played a gig and my Rm100 was working perfectly. Today we unpacked our gear and I was setting my amp up. When I turned my amp the sound was really work and I saw a flash come out of the back of my amp near where module 1 would is installed. I checked to see if a tube went bad. All tubes are 4 months old and in good condition. Next I checked all the fuses located next to the tubes. All fueses are good. I tried unplugging effects from the series send/return and just plug straight into the head. All the tubes are lit up and the channels switch but no sound.

I'm relatively certain it's something I screwed up but not sure where. When I looked at the back of the amp I realized I was plugged into the extension and not into the main out of the head. The selector switch was halfway between 8 and 16 ohm. The fan is also still running.

So to break it down:

No sound.
Fuses are all good
All tubes are working
Was coming out of extension out and not main out (first mistake)
Stuck between 8 and 16ohm switch.
Flash of light came out of the back near where module 1 would sit.

Also there was a very, very slight burnt smell not very strong. My amp is at my buddies place, we'll take a look at it tomorrow but I was wondering if anyone else might have an idea as to what might have happened and a solution?

 

[Jaded Faith]

There are several possibilities here, so you need to trouble shoot in a logical order to find the problem.

Start by making sure you plug everything in properly and have the switches set as they should be. This is where I suspect you did your damage. There should be no effects or anything but a guitar, guitar and speaker cable and speakers involved. Keep it as simple as possible.

The first test is to determine where the problem is. Plug into the input on the front and see if there is a signal. If not, plug the guitar into the series loop return. If there is no signal either way, you likely have a problem in the power section. You can plug into the input and send the series loop send out to another power amp to test if that's okay.

The bright flash, burning smell, no sound and mistakes made on the ohm switch and speaker connection lead me to think you either blew a tube or an internal fuse. My guess is the internal B+ fuse is blown. There are 6-7 internal fuses that you need to pull the amp from it's shell to access. If you are not familiar with working inside tube amps I'd take that suggestion straight to a tech who is qualified and have him locate the issue.

Hope that helps,
Rob

 

[blasure82]

There are several possibilities here, so you need to trouble shoot in a logical order to find the problem.

Start by making sure you plug everything in properly and have the switches set as they should be. This is where I suspect you did your damage. There should be no effects or anything but a guitar, guitar and speaker cable and speakers involved. Keep it as simple as possible.

The first test is to determine where the problem is. Plug into the input on the front and see if there is a signal. If not, plug the guitar into the series loop return. If there is no signal either way, you likely have a problem in the power section. You can plug into the input and send the series loop send out to another power amp to test if that's okay.

The bright flash, burning smell, no sound and mistakes made on the ohm switch and speaker connection lead me to think you either blew a tube or an internal fuse. My guess is the internal B+ fuse is blown. There are 6-7 internal fuses that you need to pull the amp from it's shell to access. If you are not familiar with working inside tube amps I'd take that suggestion straight to a tech who is qualified and have him locate the issue.

Hope that helps,
Rob

We're about 90% certain it's something internal. All power tunes light up, fuses next to the tube appear to be okay. Preamp tubes in the chasis light up as well. I haven't tried plugging into the series input so I'll do that when I go back over tonight.

 

[Jaded Faith]

I am fairly sure it will be as well, probably the B+ fuse inside. Tubes lighting up means nothing more than the heaters are working and provide very little info about the tube actually being good or not. If they are lighting up and nothing happens when you plug into the loop it's not getting the high voltage when you take it off standby.

 

[blasure82]

Wouldn't the tube failure lights light up though if it was an issue with the tubes, or is there something I'm missing?

When we get off work we'll have a look and take pics if there is any noticeable damage.

 

[Jaded Faith]

Wouldn't the tube failure lights light up though if it was an issue with the tubes, or is there something I'm missing?

When we get off work we'll have a look and take pics if there is any noticeable damage.

No, not necessarily. It's entirely possible you have blown the B+ supply fuse inside but the tubes can be 100% fine, thus no tube light to signal a short/failure there.

 

[blasure82]

So I think we may have found the culprit; a tiny tube fuse blew in this section of the amp, right behind the red-wire.

http://imgur.com/kbo9hFF


http://imgur.com/6y34JUF

Going to the local electronics store to see if they have that fuse. Here's hoping this fixes the issue.

 

[Jaded Faith]

So I think we may have found the culprit; a tiny tube fuse blew in this section of the amp, right behind the red-wire.

http://imgur.com/kbo9hFF


http://imgur.com/6y34JUF

Going to the local electronics store to see if they have that fuse. Here's hoping this fixes the issue.

That's exactly what I thought you would find, you should be okay after it's back.

 

[blasure82]

Welp at this point I've done everything I could and still no luck. There were two slow-blow fuses behind the midi-inputs that had blown as well so we went back and got replacements for those. I turned it on and let it warm up. No sound fromt he speakers, but sound seemed to be coming from the power tubes.

Upon further investigation I noticed that tube two wasn't coming to life when taken off of standby mode. I tried yanking two of the tubes running at half wattage instead but nothing... Also one of my tubes broke so I'm eyeing the amp suspiciously and suspecting I might want to get rid of it (I doubt I'll do that; I love this amp and it would be cheaper to repair than by a new amp but just not happy with it right now...)

 

[Mattfig]

I'm no amp tech by any stretch but have had a similar problem before...Check to be sure the connectors to and from the standby switch are not loose or disconnected...
Shot in the dark but you never know...In the meantime, whist poking around- check any connectors you can to make sure they are seated properly...Good luck!

 

[blasure82]

Just got word today.

The impedance selector switch somehow got damaged, causing a short and multiple fuses to blow. It's repaired now but the shop won't actually be open until Friday. Still good to hear it was something rather simple and not major.

 

[blasure82]

UPDATE: Amp is back in my hands and sounds as good as ever. The short managed to actually blow the traces off the # 3 tube but was apparently a quick enough fix.

Glad to have her back. Recording soon.

 

[kc2eeb]

Damaged impedance switch seems to be a common problem.

 

[horseblanket]

So, my RM100 died today just like the OP.
i just opened it up and the same fuse was blown.
being a novice i am not sure how to tell if my impedence switcher is bad as well but it looks like this:


Are those black marks normal?

 

[horseblanket]

and...this does not look good:



please help.

 

[jimosity]

Hmm... Might be hard to see on my iphone, but I dont see anything that looks out of the ordinary in those two pics.

 

[horseblanket]

Dang. i was hoping you'd see something. ok. need to find a tech near Long Beach. i ran out of the fx loop into my other combo so the preamp works so either power section has an issue or it's my speaker cable?
i hate not knowing. thanks for looking.