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RM50 suddenly not working? Any help?
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tnjazz
RM20


Joined: 24 Jan 2018
Posts: 47
Location: Hermitage, TN

PostPosted: Sat Jan 27, 2018 3:38 pm    Post subject: RM50 suddenly not working? Any help? Reply with quote

So I just got my new module today (an old Stonerverb) and it sounds great through the RM50.

Just went to channel switch and now I have no sound and the module lights are off (neither module works). The amp power light is still on though.

I had the speaker out connected to a Two Notes Torpedo Live and I was testing out the headphone sound. It's my understanding that the Live provides an 8 ohm reactive load to the amp, so there shouldn't be a problem there (amp was set to Cool.

Anyone have any ideas on what to troubleshoot? I've tried turning it off and on again, reseating modules, etc.

Could I have somehow nuked a transformer?
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warmachine67
RM20


Joined: 20 Apr 2017
Posts: 41
Location: Alabama

PostPosted: Sat Jan 27, 2018 4:56 pm    Post subject: Reply with quote

Maybe someone else will chime in, but aren't some internal fuses hidden inside an Rm50?

I'm guessing you tried plugging the speaker back in? Was there any hum with the speaker plugged in?

Was there a pop or noise when this started?
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tnjazz
RM20


Joined: 24 Jan 2018
Posts: 47
Location: Hermitage, TN

PostPosted: Sat Jan 27, 2018 5:14 pm    Post subject: Reply with quote

I'm about to pull the chassis and look around inside (carefully).

If I patch my AX8 line out into the amp return I get sound if I crank it up. The power tubes look good.

It appears the first 2 preamp tubes in the amp are not getting any juice. The third tube (nearest the power) is glowing though.

So I'm thinking there might be a fuse for the input section that has gone out?

Anyone know?
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Mattfig
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PostPosted: Sat Jan 27, 2018 5:17 pm    Post subject: Reply with quote

Power tubes getting any power? Oops.....Just re-reading this....

There are fuses inside, I will look for a schematic. There is an input tube V1 that is nearest your input jack....The middle on is your Loop buffer, and the one closest to the Power Tubes is you Phase Inverter....Unlikley to have those fail....
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Last edited by Mattfig on Sat Jan 27, 2018 5:21 pm; edited 1 time in total
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warmachine67
RM20


Joined: 20 Apr 2017
Posts: 41
Location: Alabama

PostPosted: Sat Jan 27, 2018 5:20 pm    Post subject: Reply with quote

I seem to remember there are four small fuses on the power switch side of the chassis hidden when it is boxed. I am not sure what they do.

At least it still makes sound Smile and it seems your OT is ok.

Sounds like whatever has your modules not working has the first two preamp tubes not working.

I'm curious what you find.
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Mattfig
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PostPosted: Sat Jan 27, 2018 5:23 pm    Post subject: Reply with quote

I have a schematic, where shall I send it?
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tnjazz
RM20


Joined: 24 Jan 2018
Posts: 47
Location: Hermitage, TN

PostPosted: Sat Jan 27, 2018 5:28 pm    Post subject: Reply with quote

Mattfig wrote:
I have a schematic, where shall I send it?


You can email me at tnjazzgrass AT yahoo

I can't read a schematic though. I have pretty much zero knowledge about amp guts so I doubt it helps me but who knows?

I've got the chassis pulled and all the visible fuses I see appear to be fine. Haven't tested them but I don't see anything obviously wrong.

V1 and V2 are not getting anything. V3 is, however. About to fire it back up again outside the combo to confirm this.
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warmachine67
RM20


Joined: 20 Apr 2017
Posts: 41
Location: Alabama

PostPosted: Sat Jan 27, 2018 5:33 pm    Post subject: Reply with quote

Guess you have some spare 12ax7s to try in v1 and v2? Probably the same result.

I'd have to see a schematic if the internal fuses are ok before I could even begin to guess what next.
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tnjazz
RM20


Joined: 24 Jan 2018
Posts: 47
Location: Hermitage, TN

PostPosted: Sat Jan 27, 2018 5:38 pm    Post subject: Reply with quote

Yes, I've got plenty of tubes. The ones in the amp were actually not the ones in it when I got it.

I did swap out both preamp and power tubes this morning. I had a JJ 5751 in V1 which should have been fine I would think. I just put the originals back in and V1 and V2 are definitely not seeing anything. V3 is, however.

Also put Mullard EL34's in place of the 6L6 and biased the amp to 30.
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tnjazz
RM20


Joined: 24 Jan 2018
Posts: 47
Location: Hermitage, TN

PostPosted: Sat Jan 27, 2018 5:56 pm    Post subject: Reply with quote

Just posted that I thought one module slot was not getting power but in fact after swapping slots it is.

That particular module has a much weaker tube complement so it didn't appear to be working but that is not the case.

So Back to square one.
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Mattfig
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PostPosted: Sat Jan 27, 2018 5:59 pm    Post subject: Reply with quote

So fill us in, do the module lights in the front work?
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Mattfig
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PostPosted: Sat Jan 27, 2018 6:01 pm    Post subject: Reply with quote

Definitely check the fuses you see for continuity....They can appear fine but still be shot...
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tnjazz
RM20


Joined: 24 Jan 2018
Posts: 47
Location: Hermitage, TN

PostPosted: Sat Jan 27, 2018 6:02 pm    Post subject: Reply with quote

No module lights, no. Tubes appear to be heating up in both slots, but no lights on either module.
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Mattfig
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PostPosted: Sat Jan 27, 2018 6:05 pm    Post subject: Reply with quote

What if you pull the cable to footswitch and try to switch in front?
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tnjazz
RM20


Joined: 24 Jan 2018
Posts: 47
Location: Hermitage, TN

PostPosted: Sat Jan 27, 2018 6:08 pm    Post subject: Reply with quote

Yup already tried that and no dice there either.

Here are a couple pics of what Iím seeing so far: no lights on the modules, power tubes and V3 working but not V1/V2 and tubes in both modules working (slot 1 is working although in the photo itís hard to see).

https://imgur.com/a/951f1
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