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Power tubes in my Budda SD18 seem to be redplating

draelyc

Gold Supporting Member
Messages
1,208
I recently got a new (matched) pair of Sovtek EL84s for it, and for the past several weeks the amp has sounded great. Yesterday, however, as I was jamming a bit in my music room, the volume just disappeared, and when I looked at the tubes, one was glowing bright red. I immediately shut down the power, and after they’d cooled off, I swapped the new tubes out for the old ones I’d had in there. Was jamming again this evening, and I didn’t have any volume drops, but I did *think* I might be smelling something heating up a bit. Looked at the tubes and it wasn’t as bad as before, but there did seem to be some red coming from the plates.

Thing is, I don’t know nearly enough about this stuff to have a guess what might be causing it, if it weren’t bad tubes. I’ll need to take it to a tech, for sure, but what should I expect the tech to look for or find? Is there any predicting such things?

Thanks y’all!
Christopher
 

easyed

Gold Supporting Member
Messages
2,560
There are several things that can cause redplating besides bad tubes. I hate to tell you to waste a pair of power tubes, but you should try swapping the tubes V5 to V6 and V6 to V5 (or whatever your numbers are) and see if the signs of redplating follow the tube or correspond to the socket.

If it's the socket, it's probably a resistor and I would take to your tech.

I recommend Russian military 6p14p tubes as the best sounding EL84 tubes available, and they are tough, but if your amp has a problem that shows in only one position, get it fixed before you spend money on good tubes.
 

vintage66

Member
Messages
6,673
I bought a set of “higher gain” tubes for my Sd30 and one or two glowed bright red and the sound faded. Turns out some of them test weak. Too late to return them as I waited a long time before actually trying them and just had them on hand as spares. Won’t be buying from that vender again though. Thing is I asked if the higher gain would handle the power of the Budda since it seams to be a high powered 30 watts and he said they would handle it better.

Bought a set somewhere else and they fine. So guessing tubes.
 

draelyc

Gold Supporting Member
Messages
1,208
Thanks for the tip, easyed — I’ll try that tomorrow. :aok

I bought a set of “higher gain” tubes for my Sd30 and one or two glowed bright red and the sound faded. Turns out some of them test weak. Too late to return them as I waited a long time before actually trying them and just had them on hand as spares. Won’t be buying from that vender again though. Thing is I asked if the higher gain would handle the power of the Budda since it seams to be a high powered 30 watts and he said they would handle it better.

Bought a set somewhere else and they fine. So guessing tubes.
Y’know, I think these were rated “medium” for earlier breakup, now that you mention it. Hmm...
 

rockon1

Platinum Supporting Member
Messages
13,201
Sounds like your tubes suffered "infant mortality". You can try swapping them around to see if its amp or tube related as suggested but my money is on the tubes. I use Sovtek EL84M's in my EL84 amps. Perhaps not the most musical (according to some but my ears cant really tell) but much tougher than the regular ones.
 

LesPaulPlayer

Member
Messages
231
I agree with rockon1's assessment. The tube that glowed bright red simply bit the dust. I've also had that happen before.

I once brought this issue of a faint red plate condition (only visible in the dark) to Jeff Bober. It's always there with my old EL84 Budda amps with Sovteks. He said it's a normal operating condition and recommended the continued use of matched standard Sovtek EL84s for a balance of tone and durability. He also mentioned that although EL84s from other countries/factories may be used, and might produce a tone that is more appealing based on a given tonal pursuit, they could bias up in a way that increased the red plating. Experimentation would be key here.

I've tried JJs and EHs and they were fine bias-wise but I prefer the tone of the Sovteks.

I make sure whatever vendor I buy from burns in the tubes and tests/matches them so hopefully the bad ones are caught before sale and they are stable in the amp. The Sovteks sound full and creamy and last as long as Jeff intended (about 6 months if the amp is rehearsed and gig'ed with weekly).

There have been numerous discussions over the past couple decades about Buddas running the power tubes way beyond what their design parameters suggest. Other designers have even scoffed at this practice and, indeed, I understand that Peavey Buddas have their biasing relaxed from Jeff's original design to achieve longer tube life based on other threads here.

On thing's for sure, my old hand wired SD30 gets sinking hot(!) but sounds and feels oh so creamy when it's been on for 45 minutes.
 
Last edited:

HoboMan

Gold Supporting Member
Messages
17,540
I used sovteks in my Buddas and some lasted a lot longer than others. I was buying from specialty tube dealers and was getting inconsistent results.

I ended up trying these guys and never had tube issues again: https://www.tubesandmore.com

Also, is your Budda a Pre-Peavey or Peavey?
Jeff Bober told me that some of the early Buddas had tube socket problems. He replaced the tube sockets on several of my Buddas. I don't recall if that's when I stopped havving issues or if it was where I was getting my tubes but after those changes I never had tube issues again (unless they wore out from usage).
 




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