6V6 line preamp

[buzzforb]

Assembly begins!

 

[brommermartin]

I would actually keep them loctal. Because you can or at least could buy cheap loctal teflon sockets.

Sent from my GT-N7000 using Tapatalk

Yes i found them, two pieces for 8 euro !!

 

[Salas]

I hope those Sylvanias will prove amongst the least microphonic then and you stay loctal.

 

[brommermartin]

I have a pair of Philips 6V6GT also so I can compare them with the Sylvania's

 

[buzzforb]

Asked in SSHV thread, but thought i would ask here too.

"Stupid question, I know. But to do final adjustements with tube attached, does the filament voltage also need to be attached. I would assume that without it, the tube is non operable."

I just wanted to quote myself.

 

[Zen Mod]

that question is stupid , if you know answer

if you don't , then it's not stupid

so - yes - tube needs hot heater for proper operation

 

[buzzforb]

First tube and voltage in hundreds, so no question is stupid. Thanks Zen

 

[Zen Mod]

yadayada
ya know .... serve & protect ....

 

[buzzforb]

Any reason why my filament voltage want go above 2V? I get 15V unloaded. I have 2.7 10W instead of parallel 15R and 3.3R. I calculated that this should be correct. Secondary is capable of 3A. What going on?
Pin 2&7 for HV, correct.

 

[Salas]

The Vh will go nominal when the Ih will be nominal through the filament (allowing for +/- tolerance). Check the voltage drop across your LM317T CCS resistor. Does it compute to nominal Ih?

 

[buzzforb]

1.25V across 2.7R is .046A. I believe the pronblem may lie in the fact that i am powering both fiaments from on regulator.

 

[Salas]

One on one and on nominal Ih. Don't string them in series with a CCS, they will auto arrange and give problems.

 

[buzzforb]

Fixing problem now! There no reason i cant use same supply with different regs, correct.

 

[pchw]

Hi Salas,

Is it possible to add links to the latest schematics of the circuits in post #1? That will make it easier to get started.

Thanks!!

 

[Salas]

Check post #1, is it OK?

 

[buzzforb]

So, with filament not hooked up, I set the SSHV2 voltage to 340 as stated on the schematic. When the filament heaters are hooked up, it drops to 300. Is this correct? i tried adjusting up with filament heaters attached and it wouldnt move. Checked again with filaments unhooked and it read over 350. Also, with secondary of trafo wire in series, using seperate regulators, i get one filament dropping 6.1V and the other dropping 5.7V. not eaxactly matched. Is this a result of sharing a secondary or mismatch of tubes?

 

[Salas]

No, its not correct, you probably need more CCS current.
For the heaters it looks more like tolerances in Ih, 317internal Vref, resistor's %. Parallel the resistor in the 5.7V one with 100R to see what happens, if it gains, find one that will give you 6.1V. That Vh is good for longer life than 6.3V also.

 

[buzzforb]

Is the B+ drop with filaments hooked up problem as well. Completely rebuilt filament supply. Will do the same for SSHV2 this week.

 

[Salas]

Try more ccs current in the reg first. If the tubes are drawing 45ma set at 65mA.

 

[buzzforb]

Sorry, misunderstood that you were addressing both problems in previous post. I am only running a single SSHV2, perhaps with second one in operation, things may change without need for adjustment. Feel pretty comfortable with what is going on now, so i should be able to work it out.