Official Universal Passive Tube PSU Thread

[tonycamp]

I see you're going at that knob with a Dremel again... It's a simple clamp nut, so:

1) leave the cap on (no need to remove it)
2) turn it all the way to the last position on the left
3) then force turn it anti-clockwise whilst pulling on it

Every rotation loosens the clamp nut a bit, and within a few turns the knob will come off in one piece.  You can also do it without pulling, and you'll see the knob slowly unscrew and move outwards.

All done in under 10 seconds, and no Dremel or round-nose pliers needed. For those who are worried, open the case first and you'll see the switch itself doesn't rotate with the knob, with the wiring remaining fully intact.

excuse the ignorance, but why would one do this ^ ? I assume there is a way to shorten the shaft without cutting it?

 

[Category 5]

Banzai was referring to Chunger using a dremel to remove the stock knob and switch.  I just use a needle nose to spin off the retaining it myself but yes, it is easy enough without destroying the stock knob. 

 

[plinker]

What do you mean "stock" vs. "upgrade"?  What is being compared to what?

Sorry.  I missed your response.

I'm comparing the stock TPS100 vs the Universal Passive PSU upgrade. 

Thanks.

 

[Matador]

This is a complete internal replacement for the stock PSU:  only the power wiring (e.g. power switch, transformer primary, ground lugs, etc) are retained.  The PSU is redesigned, and the circuit is quite different.

Major changes from stock:

1) New board has 1 more stage of filtering
2) No Zener diode in the B+ line
3) Higher quality high temp capacitors, and higher values (e.g. lower filter poles)
4) B+ is adjustable
5) LM317T heater supply, which is adjustable
6) Adjustable bias supply
7) Provisions for a negative heater voltage (wrt. ground) - mainly for U67 applications
8) Sonically superior yellow color

 

[TLRT]

Anybody tried this for Dany's U67 kit? I assume that the pattern selector's terminal can be leave as is(no cables/pattern selector attached as it is in the mic?) What is the ideal B+ resistor value for EF86 simulation? I might need this to be used for a Gefell UM57 which has got no PSU, the EC91 is actually a half ECC81, so is it ok to use it with the ECC81 setup?

 

[Matador]

Anybody tried this for Dany's U67 kit? I assume that the pattern selector's terminal can be leave as is(no cables/pattern selector attached as it is in the mic?) What is the ideal B+ resistor value for EF86 simulation? I might need this to be used for a Gefell UM57 which has got no PSU, the EC91 is actually a half ECC81, so is it ok to use it with the ECC81 setup?

Never tried one in person.

Do you have one that's operational you can measure?

 

[TLRT]

I'm just building the mic, so I'll get back to you soon! Thanks!

 

[simonstav]

Is this kit or PCB available yet?

 

[chunger]

Is this kit or PCB available yet?

Yes. . . Go to store.studio939.com and the c12 PCB set had a drop down option for "power supply pcb only".  You can also buy the donor TPS100 power supply there if you need it.

 

[Guff]

I just put together this PSU which I intend for the DU67. I stuffed R1,R2 with 18k but I'm only getting about 36VDC for B+ . The heater trims just fine to -6.3 . I'm a newb at this although I did successfully build this same PSU (V1.4) for the C12 and it works great. No idea what I need to look at. I can turn and turn R4 but can't get it past 36-37VDC. I did confirm R4 is 100k. Any help is appreciated. Thanks

 

[Matador]

Do you read 200VAC on the secondary of the transformer with it disconnected from the PCB?
Is this with or without a test load?

 

[Guff]

I'm getting 230VAC on the secondary.  I had tried to adjust B+ initially with a test load at the 7 pin jack (220k) and then again without the load and it reads the same 36-37VDC either way.

 

[chunger]

This seems like very odd behavior. . . have you triple checked the R1, R2 values?  I have this PSU running on ioaudio's MK67 kit and it has been stable.

 

[Guff]

Yes, R1 &R2 are 18k

 

[Matador]

Can you probe both sides of both R1 and R2 and tell me what the voltages are?

 

[Guff]

Matador just so I'm clear, is that R1 & R2 as a unit or each one individually? Also this would be DVC right? Thanks

 

[Matador]

Matador just so I'm clear, is that R1 & R2 as a unit or each one individually? Also this would be DVC right? Thanks

Each one individually.  With a DVM, between those 4 points and ground.

 

[Guff]

21.2 on R1 & 21.1 on R2

 

[Matador]

21.2 on R1 & 21.1 on R2

There should be 2 readings per resistor - one for each side of both R1 and R2.

 

[Guff]

R1=  37.2  /  157.3            R2 = 157.3 / 278