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RM 100 No Output Can't Seem to Diagnose

 
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Shinozoku
Lynch Box


Joined: 17 Nov 2008
Posts: 1340
Location: Bristol, VA

PostPosted: Fri Apr 13, 2018 9:38 pm    Post subject: RM 100 No Output Can't Seem to Diagnose Reply with quote

I have a Randall RM100 and a week or so ago, my output just cut out completely. The only sound I can get out of the amp is similar to feedback. I have tried using the effects loop and slave out to test preamp vs power amp, but I can not get the Randall to produce any sound. I've tested all fuses, as well as visual inspection of the boards, but I am at a loss as to what the issue could possibly be. Any help is appreciated! Thank you!!!
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RM100M w/ Tung Sol 5881's
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Vader 2x12 Cab
Edwards E-AL-128 with a Seymour Duncan JB
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Ruddwiijk
RM20


Joined: 24 May 2018
Posts: 4

PostPosted: Fri May 25, 2018 8:24 am    Post subject: Reply with quote

Did you get anywhere with this? I'm planning to look into a problem that appears similar this weekend.
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Shinozoku
Lynch Box


Joined: 17 Nov 2008
Posts: 1340
Location: Bristol, VA

PostPosted: Sat May 26, 2018 11:53 am    Post subject: Reply with quote

Yes and no. I blew R3 on the power board. It is a 5w resistor. I replaced it and tried again, but it blew almost instantly. Same resistor. It seems to tell me there's a dead short to Ground somewhere downstream. I've checked the circuits around both places it goes to the tube board (preamp side) with no issues found. The schematics I was sent from Randall are not 100%, so I'm getting ready to trace down the last bit of circuitry past that resistor, though I'm not sure yet where it goes (only have tube board, power board, and schematics in front of me at the moment) I am almost certain it is not ether of those boards. That 5w resistor blows too quick for it to be anything but a short to Ground I think. I feel like I'm I'm getting close to figuring out this $@$_#@#$#@$# been very frustrating!
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RM100M w/ Tung Sol 5881's
Blackface(self modded), Ultra Lead, SL+(out of commission), Ultra XL (self modded)
Vader 2x12 Cab
Edwards E-AL-128 with a Seymour Duncan JB
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galao
Donating Member


Joined: 05 Dec 2008
Posts: 111
Location: Berlin, Germany

PostPosted: Sat May 26, 2018 1:17 pm    Post subject: Reply with quote

The issue could likely be caused by a shorted power tube. Did you check that?
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Shinozoku
Lynch Box


Joined: 17 Nov 2008
Posts: 1340
Location: Bristol, VA

PostPosted: Sat May 26, 2018 2:55 pm    Post subject: Reply with quote

I tested the pins with a multimeter, verifying that only the plate pins (2&7) had connectivity. I have given the tubes to someone with a proper tube tester, but there's no direct short in them (without power)
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RM100M w/ Tung Sol 5881's
Blackface(self modded), Ultra Lead, SL+(out of commission), Ultra XL (self modded)
Vader 2x12 Cab
Edwards E-AL-128 with a Seymour Duncan JB
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galao
Donating Member


Joined: 05 Dec 2008
Posts: 111
Location: Berlin, Germany

PostPosted: Sun May 27, 2018 7:37 am    Post subject: Reply with quote

Bummer.. That would have been a rather easy fix. I had the same issue caused by a shorted power tube a couple of years ago. Hope itīs not the OT in your case..
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