TMB with EL34s

Post by **zaphod_phil** » Sat 11/27/10 11:26 pm

Could also be a bad tube....

insanecopilot · Post by **insanecopilot** » Sun 11/28/10 9:13 pm

zaphod_phil wrote:Could also be a bad tube....

Probably could be or non matched tubes. this pair is not matched. Looks like i am ordering tubes once again.....

Anyway I am side tracked once again with a VHT special6 to 18watt Lite2 conversion I'm covering in another thread.

Post by **zaphod_phil** » Mon 11/29/10 8:52 am

They would have to be really badly un-matched to have a bad effect on the sound. Some mismatch will generally make the tone harmonically richer and warmer.

The 150 ohm resistor will also get hotter when the tubes are biased tp draw more current. So that may not be anything wrong either.

insanecopilot · Post by **insanecopilot** » Fri 02/25/11 10:11 am

I finally got back to this amp which has been sitting by the wayside, just cant seem to find the overheating problem. I probably bit off more than i can chew by making too many changes to the basic layout and decided to start over. the board is out already. I'm not sure if i trust the origional crate pt. On the origional blue voodo schematic it had some sort of a 100uf /100uf bootstrapped at the b+, with a full wave bridge recto after it. Dont know if this is where my problem is comming from. so......starting over. I have two pt's on hand. A hammond 272fx 300-0-300 150 ma. And a edcor xpwr109. 275-0-275 175ma to work with. Also have the stock crate 6l6- el34 ot which is beefy for a crate. Or i can say screw it and make it an 18 superlite tmb with the classictone 18 watt ot i just got. Based on the iron i have what would be my best route?

insanecopilot · Post by **insanecopilot** » Sun 02/27/11 7:02 pm

Found my problem, I had the 8k2 rail resistor grounded and not wired to the 100k plates. Wired wrong under the board is why i missed it.

It's a wonder it made any sound at all.

going to use the 272 fx pt and crate ot. Think i still can use the el34's or 6L6's (i have both).

Dustpuppy · Post by **Dustpuppy** » Mon 02/28/11 10:17 am

Cheers!
I've had a few run in's with under board wiring. On a suggestion from someone here, I started running my B+ above board, under the components and I've had great luck.
I built a pentode 18 watt a while back using EL34's and it's become my primary gig amp.

insanecopilot · Post by **insanecopilot** » Mon 02/28/11 11:57 am

Yea dp i remember. I also built a 6u8 18watt and love that one.

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TMB with EL34s