diytube.com

Locktals should be easier to wire since the pinout is "mirror image", plus get NOS for dirt cheap.

That plate that replaces the PCB only cost $27.00 from Front Panel Express.

For my 300B SET on a ST70 chassis, I used some scrap aluminum, cut it to the right size, and used it to mount the 2 tubes SRPP driver turrent board underneath. It doesn't look as nice as the FPE professionally made version, but for my purposes, it was more than good enough for the job.

I did the initial cutting / sizing with a hacksaw, and then cleaned uo the somewhat rough edges with a file and sandpaper, and the drilling was easy. I have several more of these scrapped small aluminum plates, which will end up in futiue tube amp designs (and one, cut in half, served as the front panel for the "Uglytron" 6SL7 / 6L6GC se guitar amp, and the other half of the plate serves as the FP for a very basic 24VAC, 2A PS to operate a couple of ultrasonic foggers.

With the 7F7 / 7N7 driver, I'd use the LM334Z CCS, or a current diode, and 62K or 68K plate resistors. I've got a LOT of 68K, 2W 5% resistors, these are in a bulk package, that I snagged at a flea for a $ a few yearsd ago. These are PIHER brand, made in Spain, the box originally contained a thousand of them, the original owner(s) use maybe a dozen or so...

/ed B

TerrySmith wrote:That plate that replaces the PCB only cost $27.00 from Front Panel Express.

And for those handy with aluminium and have Greenlee's, about a $1

I've gotten on a "loctal kick" lately.

Hey Ed, I have some NOS in box 5B/254M doing nothing but being apartments for spiders. Wanna trade for something?
(free choice of hobo or black widow for a "pet" )

Cheers!

TerrySmith wrote:Thanks for the complements! That is a deal for a '70, especially with the original tubes.

The SDS board is basically the stock 7199 circuit but laid out to use a EF86 / 12AU7 combo. Should sound better than stock since the EF86 is a better tube than the pentode section of a 7199.

Yeah I knew it was a deal when the guy offered to sell it to me for $10, but I played dumb so I could get it for that price...haha. Thanks for the heads up on the SDS board. This will be fine for me for my first ST70 and if I want to play around I can put together another from Triode parts and try a different circuit I guess. I'm curious how it will compare to the Scott 299B that I have to restore too.

Greg

And for those handy with aluminium and have Greenlee's, about a $1

I am out of sheet aluminim right now. About 10-12 yrs ago I found a 3' x 3' piece of .080 aluminum at the scrap yard and it lasted for many projects!

Need to get more as I have a fairly nice Heathkit AA-100 with burned up circuit boards and I want to rebuild / modify it using point to point wiring. Seems like every (4 or 5) AA-100's I've had the PCB's were burned to a crisp.

I just got a piece of 2' X 6' 0.064 for $15. Last week I went through my 2 sheets of 0.05. Need to go back and find some 0.100 or 0.125.

Hey Ed, I have some NOS in box 5B/254M doing nothing but being apartments for spiders. Wanna trade for something?
(free choice of hobo or black widow for a "pet" )

Cheers!

Whatcha need? I could be interested in swaps. Black widows and hobos are OK, just no brown recluse "fiddleback" or Australian funnel web spiders, please...

/ed B

EWBrown wrote:

Hey Ed, I have some NOS in box 5B/254M doing nothing but being apartments for spiders. Wanna trade for something?
(free choice of hobo or black widow for a "pet" )

Cheers!

Whatcha need? I could be interested in swaps. Black widows and hobios are OK, just no brown recluse "fiddleback" or Australian funnel web spiders, please...

/ed B

No funnel spiders and you'll have to wait until July here for fiddlebacks... too wet right now

Little tubes... I seem to have traded or blown up "disposable brands" of 6DJ8 and EL84 for R&D
(Westinghouse, Rogers, International, things that work but don't command $ )

** edit **

Got a 12SL7?

Cheers!

If I wanted to use a 6SL7 in place of the long tail 6SN7 what changes would I make to C8 and R49? The Mapletree design uses a 6SL7 long tail and uses a 21K resistor and 150pf.

I'm in the process of trying to design an all 6SL7 driver board so any help would be appreciated.

The Mapletree circuit and the Ike circuit are basically the same except the pentode front end, and the part values to suit the 6SL7 PI.

Looking at the Ike fixed bias scematic change:
R9, R10 to 150k
R6 to 432k
R7 to 54.9k
C2 to 1uf @ 400v
If using in a ST70 change the power supply 22k resistor to 200k

This should get you headed in the right direction.

Thanks I have all those values already. I am concerned with C8 and R49

where did you install the cl90?

nice job!

Geek wrote:

EWBrown wrote:

Hey Ed, I have some NOS in box 5B/254M doing nothing but being apartments for spiders. Wanna trade for something?
(free choice of hobo or black widow for a "pet" )

Cheers!

Whatcha need? I could be interested in swaps. Black widows and hobios are OK, just no brown recluse "fiddleback" or Australian funnel web spiders, please...

/ed B

No funnel spiders and you'll have to wait until July here for fiddlebacks... too wet right now

Little tubes... I seem to have traded or blown up "disposable brands" of 6DJ8 and EL84 for R&D
(Westinghouse, Rogers, International, things that work but don't command $ )

** edit **

Got a 12SL7?

Cheers!

I've got a bunch of used 12SL7's myself. I stuck them in boxes in the attic along with other stuff I can't readily use and might be able to use at a later date. Were you looking for new ones or used ones?

Greg

Hi,

Both.

June's acquisition budget is blown already though and looks like our post is going on strike. So I'll shoot you a PM 2nd or 3rd week in June for July's acquisition

Cheers!

Well this '70 has performed flawlessly since the rebuild except the power transformer is getting noisy as they all do.

Edcor has a transformer that is X mounted but will bolt in the 3.75x3 pattern. Also there's no 5v winding, doesn't matter for me as I use SS diodes on this one. One plus is the 400ma secondary, maybe I could roll in KT88 or 6550 tubes and bias them hotter.

XPWR214-120


Power transformer for a 120V, 60Hz. line to 720V with 70V bias (360-0-70-360) at 400mA center tapped and dual 6.3V (3.15-0-3.15) at 4A center tapped.

Any thoughts or opinions ?