HELP, Hotrod Deville eating tubes!

ray · June 27th, 2003, 10:09 AM

I need help with a tube problem in my Hotrod DeVille 212. It seems to be eating power tubes, I start to get a jingly sound when I play bass notes, sounds like an old telephone ringer, the amp also seems to have lost some volume. This is the second set of tubes that this has happened to. The tubes are JJ Tesla 6L6GC's and I had the bias set correctly for them. I also replaced the speakers with Celestion Greenbacks, and the frames of those speakers are a bit larger than the Fender speakers, so one of the transformers touches the frame of the speaker. Could the vibration from the speaker be rattling the life out of my tubes?
Thanks for any suggestions.
Ray

MJ Harnish · June 27th, 2003, 01:12 PM

The vibration could very well be causing the problem since once tubes get hot they're more prone to damage from jarring or vibration. It certainly can't be good for them to be vibrating sympathetically with your speakers though the idea of them "grooving with your jam" may sound cool. :D

Have you tried rotating the speaker so that the transformer falls in between holes in the frame? If so and that isn't possible, you might have to replace the speaker with something smaller.

That said, it could be something else. First off, how did you set the bias? What I mean is did you measure the plate voltages and make sure you're falling within the tubes plate dissipation specs? If you're just setting the bias voltage to an arbitrary value (e.g., the one listed on the schematic) you could be running the tubes out-of-spec (though that's unlikely).

ray · June 30th, 2003, 08:43 AM

Thanks for the reply MJ Harnish ,
I pulled the speaker out and had to drill four in between holes so I could mount it with the frame in a different spot (Celestions come with only four mounting holes). I still think I have a powe problem, seens like the amp drops in volume as it gets hot after about an hour or so, the pilot light get a bit dim, if I shut it off and let it cool the light comes back on brighter. What do you think?
Ray

MJ Harnish · June 30th, 2003, 09:11 AM

Hmmm, it does sound like something else is amiss. This could be a completely unrelated problem or you could have jiggled something else free while you were rocking. I think it might be time to take the amp to a competent tech... :(

June 27th, 2003, 10:09 AM	#1 (permalink)
ray Tele-Meister Join Date: Mar 2003 Location: Buffalo Age: 54 Posts: 149	HELP, Hotrod Deville eating tubes! I need help with a tube problem in my Hotrod DeVille 212. It seems to be eating power tubes, I start to get a jingly sound when I play bass notes, sounds like an old telephone ringer, the amp also seems to have lost some volume. This is the second set of tubes that this has happened to. The tubes are JJ Tesla 6L6GC's and I had the bias set correctly for them. I also replaced the speakers with Celestion Greenbacks, and the frames of those speakers are a bit larger than the Fender speakers, so one of the transformers touches the frame of the speaker. Could the vibration from the speaker be rattling the life out of my tubes? Thanks for any suggestions. Ray

June 27th, 2003, 01:12 PM	#2 (permalink)
MJ Harnish Tele-Meister Join Date: Mar 2003 Location: Hattingen, Germany Posts: 457	The vibration could very well be causing the problem since once tubes get hot they're more prone to damage from jarring or vibration. It certainly can't be good for them to be vibrating sympathetically with your speakers though the idea of them "grooving with your jam" may sound cool. :D Have you tried rotating the speaker so that the transformer falls in between holes in the frame? If so and that isn't possible, you might have to replace the speaker with something smaller. That said, it could be something else. First off, how did you set the bias? What I mean is did you measure the plate voltages and make sure you're falling within the tubes plate dissipation specs? If you're just setting the bias voltage to an arbitrary value (e.g., the one listed on the schematic) you could be running the tubes out-of-spec (though that's unlikely). __________________ MJ Harnish Suburbs: Where they cut down all the trees and then name the streets after them.

June 30th, 2003, 09:11 AM	#4 (permalink)
MJ Harnish Tele-Meister Join Date: Mar 2003 Location: Hattingen, Germany Posts: 457	Hmmm, it does sound like something else is amiss. This could be a completely unrelated problem or you could have jiggled something else free while you were rocking. I think it might be time to take the amp to a competent tech... :( __________________ MJ Harnish Suburbs: Where they cut down all the trees and then name the streets after them.

June 30th, 2003, 08:43 AM	#3 (permalink)
ray Tele-Meister Join Date: Mar 2003 Location: Buffalo Age: 54 Posts: 149	Thanks for the reply MJ Harnish , I pulled the speaker out and had to drill four in between holes so I could mount it with the frame in a different spot (Celestions come with only four mounting holes). I still think I have a powe problem, seens like the amp drops in volume as it gets hot after about an hour or so, the pilot light get a bit dim, if I shut it off and let it cool the light comes back on brighter. What do you think? Ray