Dead RM100 - Correction - still need help

[KillTone]

Since I got my RM50 I have let the RM100 sit for about a month. Last time I turned it on it worked, after sitting for a month - nothing.

I checked all of the obvious stuff - guitar, guitar cable, speaker cable, speaker cab, tube indicator lights. All are fine.

When I check the bias I get no reading on my meter. The tubes all glow. If I turn the bias adjustment there is no visible change in the tube (usually there is at the extremes).

I have noticed that when I flip the standby switch to "play" I can hear a faint pop in the speaker - just like I would hear when the amp works.

I do not have much spare time right now so I am hoping that someone can point me to some quick diagnostic things to figure this out.

If this is a fuse issue - can someone please tell me the size/values I will need. I have bunch of fuses for the power tubes. Will those work everywhere?

Thanks,
Ron

 

[KillTone]

No ideas out there?

 

[JKD]

Do you run anything in the FX loop?

Just insert and remove and plug from the series FX loop...in fact you can jumper the FX loop Send -> Return and try it...

I've only had and amp go out once because of lack of connection in the loop..but it does happen.

 

[KillTone]

I'll try it thanks.

FYI - Right now I am just trying to get sound out of the amp so I am not using the FX loop. I do use it at gigs.

Thanks again.

 

[JKD]

AH..sorry I re-read your post....sounds like one of the HT fuses has gone..am guessing it's internal but I don't know anything about amps really...did you check Pete's big fuse location thread?

Always test fuses with a continuity meter....some can look 'OK' but are blown.

The values/types are on teh end-caps of the fuses...if you're not comfortable poking around inside amps...take it to a tech,

 

[KillTone]

Thanks for the follow up. I think I know what it is. There has been something loose related to the standby switch that was causing an intermittant buzz. I think it totally came undone. I'll have to open it up and take a look.

I'm not good with a soldering iron, but I am comfortable looking at this stuff. Hopefully it is a spade plug or something that does not require solder. If so, it's off to the tech next week.

 

[KillTone]

Well, after opening it up the area around the standby switch is way too full of wires and connections for me to feel comfortable poking around in. I did find some loose, but still connected spade plugs that i tightened up, but that is all I am going to do.

**** - I really want to hear the Voodoo Trainwreck module I just got back. Looks like I have to dig the RM50 out of the gig trailer.

 

[Bewitagos1]

Thanks for the follow up. I think I know what it is. There has been something loose related to the standby switch that was causing an intermittant buzz. I think it totally came undone. I'll have to open it up and take a look.

I'm not good with a soldering iron, but I am comfortable looking at this stuff. Hopefully it is a spade plug or something that does not require solder. If so, it's off to the tech next week.

I don't know if anyone else pointed this out or not, but there are some circuits in there holding enough potential to kill ya - even with the head unplugged.

If you do pull the chassis and check the fuses, there are two .400 mA near the midi circuit board that blow, the tubes will still light up and the amp looks functional, but there will be no output to the speakers.

Good luck,
Jimmie

 

[KillTone]

Thanks Jimmie:

Yes, I am aware of the dangers. That is why I only went so far and decided to call off my search. Thanks for the tip on the fuses. I'll try those tonight and maybe spare myself a trip to the tech.

Ron

 

[bruce egnater]

Plug your guitar into the effects loop return. If you get any sound, the power amp is working.

 

[KillTone]

Thanks for the tip Bruce! This helps because I have been too busy to get it to my tech. He does tech work out of his home after his regular job and I have a 2 hour window to get it to him on weekdays.

I tried that and did get sound. What is my next step? All of the 12ax7's on the chasis light up when the amp is on. What am I bypassing when I plug into the efx loop like that?

Thanks again!

Ron

 

[bruce egnater]

You are bypassing the preamp and the effects send. This tells us the power amp and effects return are good. Would also indicate the power supply is OK. Do you get any sound at all from the preamps? Hiss? Any hint of guitar sound at all? What steps have you taken since this happened? Replaced any tubes? If so, which ones?

 

[KillTone]

Thanks again Bruce.

Nothing from the pre-amps at all.

I have not done much due to limited time. I tried replacing all of the 12ax7s on the chasis, that did not help. The only other thing I have done is to take the amp out of the headshell and visual inspect for any obvious disconnects or bad parts.

I should probably explain that I have had an intermittant problem with the standby switch. The amp would have a grounding hum when played loudly (loud enough for it to rattle something loose?). If I tapped on top of the head the hum would go away. It would also go awa if I cycled the stand by switch - no matter how quickly.

Since the "no sound" problem came up, I did notice that if I tapped on the head with the right module out (closest to the switches) I could see the light from a spark coming from somewhere around where all of the wires are bundled near the power and standby switches.

I know I probably should have never tapped on the amp, but sometimes the buzz was intolerable during quiet parts of my gigs.

 

[Julia]

Was that a light tap? or more of like whapping the side of an old tube TV?

 

[KillTone]

The lighter side of somewhere in between.

 

[kc2eeb]

Check the screws that fasten the power supply/filter board to the chassis.
(You'll have to remove the amp from the box)
Make sure they're properly tightened.
I my own RM50 (I think the RM100 is similar one this) two of those screws are used as the ground for the heater supply voltage regulator and if they're not secure you will get a loud hum and can be intermittent.
It will hum even with the volumes off.
Hope this helps.

 

[Bewitagos1]

The lighter side of somewhere in between.

did you check for continuity on the switch? tapping it may have eventually bent the contacts, if not, am still betting you still have a blown fuse or worse, a cold solder joint.