replaced internal fuse and RM100 still dead

[sun spot]

I have a RM100 that would power up, with fan running and lights on, but the power tubes (KT88) didn't glow (and no sound when taken out of standby to play). No tube failure lights were on and I checked all four tube fuses and the main AC fuse, all OK. I pulled the chassis and found a blown fuse, which I believe is a heater fuse. I replaced it with a 10A slow blow, as recommended by Bruce Egnater in a post. Now the power tubes glow in standby, but still no sound. Any suggestions

 

[6stringgrind]

How long did you try to play it afterwards? The last time I changed a heater fuse, the amp didn't make sound for a few minutes until I cranked the master volume, then it suddenly kicked in with a howl. About blew my freakin' eardrums!

By the way, if I were you, I'd have a good amp tech take those fuses out of the path. Otherwise, you may be taking that chassis out quite often.

 

[sun spot]

I had read your post about your master volume technique, so I ran the amp into my HotPlate attenuator and tried it a couple times, but it didn't work. I was reluctant to use that technique anyway.

 

[kc2eeb]

When you check the other fuses, make sure you check them all.
Also, don't just check them by eye, use a multimeter.
Make sure the impedance switch is functioning correctly.
Then, check the plate resistors. Are they passing HV.
Please, if you have no experience with high voltage, let a tech do it.
Also, check your cables and connectors, with a meter, for continuity.

 

[Mailman1971]

I had that happen to me as well. Did the amp play with the KT88's before it died?
When I switched from EL34's to the KT88's I swapped the tubes...
went to fire it up to bias it...nothing. just powered up like you mentioned.
I had to put a pair of EL34's back in to get it to "spark" to life....
then I could bias the one pair of KT88's up to level. Then I shut it back down....pulled out the pair of EL34's, replaced them with the 2nd pair of KT88's and it fired up to let me bias them. Something about the Bias level of the El34s wouldnt get the KT88's working.
Seems like a long drawn out process but it worked for me and took about 15 minutes once I went crazy trying to figure it out. :wink:

 

[sun spot]

I had been using the KT88s for about a month without incident. Now it is actually producing some sound, although very very quiet. If I almost max out everything I can hear it, but that is of course inviting disaster. I'm going to try putting in some 6L6s and see what happens.

 

[voodoomyk]

Did you ever get yours fixed? Mine is doing the same thing.

 

[sun spot]

No, I haven't gotten it fixed. I seemed to run into a dead end and got frustrated. I'm in Michigan, so I had hoped to take it to Egnater, but I saw on their site that they're too busy to work on stuff. If anyone knows any good repair guys who know what to do with these crazy amps, I'd like to get this fixed. I've got a fleet of other amps, including a RM20, so it was easy to leave RM100 collecting dust.

 

[MYDEMISE]

I live in south east Michigan. Where did you find the 10 amp slow blow mini internal fuzes? Radio shack sure doesn't havem

 

[sun spot]

I found the fuses locally in Kalamazoo (!) at a place called Ken's Electronics. It's kind of like the best Radio Shack from the 70's. He's got a website:
http://www.kenselectronics.com/index.html