My RM-100 is Dead!

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Corium_AZ

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Well godammit, my RM100 took a crap on me tonight. Was playing at my normal volume thru my silent rig - THD Hotplate as load box, direct out to my interface, etc... In any case, it just shut right down on me. No power at all. No power led lights when the mains switch is on. No fuse led's. Nothing. Checked all tube fuses, all good. Promptly Removed chassis, checked all internal fuses. All good to go. No smoke, no smells, no burnt resistors or pcbs. Looks as new inside. Of course this happens at 2am, and I have band practice tomorrow...

So, at this point I guess I have to assume I either fried the PT or lost a cap. I'm no electronics expert, but pretty good at figuring things out & fixing issues. So, how do I test a Xformer? And, is there anything else I should look for/at?

Any help is appreciated for sure as I don't think I can live without it for too long. It is my only amp. I suppose I'll be using my lead guitarists JMP until I can get this sorted out. Oh, the horror, I know, lol!
 
Check the simple stuff first. The speaker impedance switch, speaker cable (with a meter), do that first.
 
Unless I missed it.. I didn't see that you checked the main fuse. Did you?
 
warlok said:
Unless I missed it.. I didn't see that you checked the main fuse. Did you?

Had exactly same thought myself.

Pull the fusebox right by the mains cord....note that it's able to be put back in many ways..the little arrow next to it should currently be pointing to the 120V markings n it...put it back that way (if you are in US of course!)
 
Check the AC cord, the wall outlet for voltage, etc.
Also, check the fuse with a multimeter, not just visually.
 
kc2eeb said:
Check the power switch switch on the amp for continuity?

Didn't think of that, but I'll test it tonight. Not sure how something like that would fail randomly, but stranger things have happened I suppose.
 
Ok, well I got it fixed last night... It was in-fact the mains fuse after all. Strange thing, it checked out on continuity test, but had very high resistance. Maybe partially blown? I dunno, very strange. But I threw in a new fuse and fired right up & plays just fine. Like nothing ever happened. Weird, but I'm happy!
 
There you go. Fuses can be defective like anything else. BTW, when it measured very high resistance was it in the megaohms?
Were your fingers in contact with both of the probe tips?
You might have been measuring your own body resistance.
 
kc2eeb said:
There you go. Fuses can be defective like anything else. BTW, when it measured very high resistance was it in the megaohms?
Were your fingers in contact with both of the probe tips?
You might have been measuring your own body resistance.

It was in Mohms, iirc. I measured while it was still in the plastic 'holder' dealio. Thing is, it checked out on continuity, so I just moved on. And, the filament appears in-tact & no burn marks on glass or anything. Looks brand new. Rather strange IMO, but just glad I checked it instead of start replacing parts, lol.

Thanks for the help/suggestions. It is appreciated.
 
At one time, "long ago,"a defective fuse was very uncommon. Not anymore.
I'm just as guilty as anyone else in not following the "standard troubleshooting sequence" and thinking it's a worst case scenario, but it really pays to check the obvious. Having to replace a transformer is actually a rarity. Having said that I did replace the OT and PC board on my RM50. Glad I did it when they were still easy to get.
 
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