dcribbs1412 wrote:
great info...I'm gonna keep on eye on the JJ 6CA7's biased at 32ma
in there for now...my PT is about 10V less at 455V.The 6CA7's seem to create a lot more heat than the KT 77's. Would love to try the RFT's someday when I have the cash.
I will keep the classic bias board idea close in case something else happens.
Appreciate your time
Darin
Darin, I have the big bottle JJ 6ca7 in my latest high voltage build. It has around 715v on the plates, biased around 26 and they have been stable. Yes I found that as well, they do emit a fair amount of heat. I transfered my 183 with Genelex KT77's to a taller head cab and I plan to do the same with that HV build as well.
Mike
ToneMerc wrote:
Darin, I have the big bottle JJ 6ca7 in my latest high voltage build. It has around 715v on the plates, biased around 26 and they have been stable. Yes I found that as well, they do emit a fair amount of heat. I transfered my 183 with Genelex KT77's to a taller head cab and I plan to do the same with that HV build as well.
Mike
Hi Mike
I was looking at the Genelex KT77's decided to go with the cheaper JJ's.
Thinking about a small clip fan on the back of the head cab. Next head cabs
will be taller...say maybe 2in.
appreciate the info
ToneMerc wrote:
Darin, I have the big bottle JJ 6ca7 in my latest high voltage build. It has around 715v on the plates, biased around 26 and they have been stable. Yes I found that as well, they do emit a fair amount of heat. I transfered my 183 with Genelex KT77's to a taller head cab and I plan to do the same with that HV build as well.
Mike
Hi Mike
I was looking at the Genelex KT77's decided to go with the cheaper JJ's.
Thinking about a small clip fan on the back of the head cab. Next head cabs
will be taller...say maybe 2in.
appreciate the info
Darin
My early gen hybrid in the snakeskin cab I had built IIRC is 1.25" taller with two oval vent ports in the front. I need to have that cab cloned for my HV builds.
On some of my HV builds I'll install a 12 VDC computer (brushless) fan between the Pwr and output Xformers (near the front) they are cheap and run them right off the 12V regulated supply..You don't want them 2 close to the pwr tubes, just enough to get some air circulating...The 230 MM pwr doesn't really get too hot but the tubes will..I've also installed some in some amps that use FWB where the trannys can and do get hot run for longer periods cranked up..They Will help with tube life in any amp..
BTW..Darin that is strange you had 2 tubes do that at the same time and on the same side of the OPT..Do keep an eye on those big bottles
I had an amp do a similar thing and it turned out to be a hair that was laying down in a socket wreaking havoc on the bias supply..Weird
Good Luck All
Tony
" The psychics on my bench is the same as Dumble'"
talbany wrote:On some of my HV builds I'll install a 12 VDC computer (brushless) fan between the Pwr and output Xformers (near the front) they are cheap and run them right off the 12V regulated supply..You don't want them 2 close to the pwr tubes, just enough to get some air circulating...The 230 MM pwr doesn't really get too hot but the tubes will..I've also installed some in some amps that use FWB where the trannys can and do get hot run for longer periods cranked up..They Will help with tube life in any amp..
BTW..Darin that is strange you had 2 tubes do that at the same time and on the same side of the OPT..Do keep an eye on those big bottles
I had an amp do a similar thing and it turned out to be a hair that was laying down in a socket wreaking havoc on the bias supply..Weird
Good Luck All
Tony
Tony
Great info
Do you run relays off the same 12V PT?
I think I have some 5V DC fans.
Will keep an eye on the tubes for sure.
I have picked a few hairs out of a few of my builds(I haven't had a hair cut in over 25 years...) Didn't realize the problems that could cause
Thanks for your time
Darin
dcribbs1412 wrote:I haven't had a hair cut in over 25 years...
Darin, that is amazing.
And I can't believe your tubes went at the same time as your mod. Do you think you banged them up moving the chassis around?
Hi Taylor
Its possible but I try to stay careful around amps on the bench...even when they are not powered up. Might be time to build a decent chassis stand. Its weird the 2 "bad" tubes still match around 50ma...
BTW I don't want to sound like a wildman that
has no personal sense of hygiene...I've had my hair pulled back since
I can remember...Oh and I have a semi-respectful job...
