Official Universal Passive Tube PSU Thread

[snaredrum]

hi sorry for my english , i live in france  and it's not easy for me to converse ) . I have the C12 matador kit diy and it's ok for the transformer but i can't find built scheme about V1.4A C12 mic circuit board and it is very different of V1.1A , so if you have a links with instruction and picture for V1.4A circuit board , i will be very happy .  regards

 

[Matador]

Most of what you need is here:

https://groupdiy.com/index.php?topic=51377.0

Check in the last 10 pages or so.

 

[trans4funks1]

Hello,
What is the status and or availability of the final design PCBs?

I thought they would be on the Studio939 site but do not see them offered.

Thank you.

 

[Matador]

It's the C12 PSU on Chungers store: the latest C12 = the universal passive.

 

[trans4funks1]

Now I see it.

at: http://store.studio939.com/product/c12-vintage-microphone-clone-pcb-set

there is a drop down in the bottom right corner where I can select "Power Supply Board Only".

Thank you.

 

[maq3396]

Hello,

Has anyone tried, or know if it is possible, to configure this for Poctop's M-49b/c?

Thanks
Mac

 

[TLRT]

Hello,

Has anyone tried, or know if it is possible, to configure this for Poctop's M-49b/c?

Thanks
Mac

M49 needs a choke I think(the "b" for sure) for ac701 mics the panel is ok, I build a km56 PSu using this

 

[Matador]

This PSU should work fine for the M49.  The B+ is specified at 116V @ 0.75mA, which is easily doable.  The heater supply is rated at 4V @100mA, and is within the adjustment range of the heater supply.  I don't think any BOM changes are necessary.

 

[Ericbazaar]

This PSU should work fine for the M49.  The B+ is specified at 116V @ 0.75mA, which is easily doable.  The heater supply is rated at 4V @100mA, and is within the adjustment range of the heater supply.  I don't think any BOM changes are necessary.

Its working very well for my M49 Build with EF762/732/5840 Tube.

 

[maq3396]

Thanks!
May I ask what values you enede up using for R1 and R2?

 

[Matador]

Eric can answer, but 116V @ 0.75mA is VERY close to the C12 operating point (120V @ 0.7mA with a 6072A tube), so the stock 68K value for R1 and R2 should work in the M49 case.

 

[Ericbazaar]

Eric can answer, but 116V @ 0.75mA is VERY close to the C12 operating point (120V @ 0.7mA with a 6072A tube), so the stock 68K value for R1 and R2 should work in the M49 case.

for EF762/732/5840 i've changed R1 and R2 to 33k. Circuit is build after Oliver Archut's TLM49 to M49 Conversion
http://www.tab-funkenwerk.com/id183.html
for R1, R2 and R5 in Oliver's Schematic i use 1G Resistors instead of 100M.
And change C5 to 10uF 63V (25v work well).

 

[Matador]

Ahh yes, different tube than the AC701.

 

[Neutrino]

Hi Matador,

just to confirm: I should be able to use a trafo with 6.3V secondary (instead of 9.5V) with your v1.4 PCB, right?
It just means that the regulator will have to be adjusted accordingly, i.e. not to down-regulate the voltage. This is what I intend to use:

https://www.tube-town.net/ttstore/Transformer/Power-Transformer/Toroidal/Toroidal-30VA::2192.html?language=en

Cheers and Happy New Year 

 

[sl]

Hi Matador and Chunger,

I plan to use this PSU with my C12VR mics, schematic attached. I have 2 questions:

1. When I measure Pins 5 (B+) and 7 (GND) on the mic socket without any power to the mic, I get about 900K on both mics. Based on the attached mic schematic, is this normal?

2. What value resistor should I use between Pins 1 and 7 on the PSU to adjust the PSU prior to hooking up the mic? The same 180K 1W as per the photo posted in the tutorial above?

3. What should the values of R1 and R2 be?

Thanks,
Steve

 

[sl]

Hi Matador,

The PSU PCB is a work of art. Thank you for making it available.

I built it on a new and unmodified Apex 460B PSU (which worked well with the stock 460B mic which has an 12AX7B tube) according to Chunger's excellent instructions on this thread and followed it exactly. Please see attached picture of my build. P6 on the PCB is connected to the ground pin on the 7-pin XLR. I used a 180K resistor in Pins 1 & 7 to first adjust B+, checked heater. Both are within what you indicated in the thread. I noticed that on the stock PSU, bias is shorted to GND so I left it that way as my first test is to be with the 460B. With the wire to P4 disconnected from the 7-pin XLR, I could get a –ve bias voltage but it did not seem to respond.

Since the stock Apex 460B PSU has bias shorted to GND, I did not think it mattered and connected the Apex 460B to it.  B+ ramped up nice and slow and I got it to 135V which is what stock PSU supplied. Filament is at 6.26V which is just fine.

However, I get no modulation output. 2 questions:

1. What am I missing?

2. Also, with P3 on the header marked as being “Polarization” and P4 as “Bias”, which pins do they correspond to on the C12VR in the schematic I attached in the last post?

Thanks for offering a great build, and in advance for your support.

 

[Matador]

There are a few things:

1) That C12VR is cathode bias, so you don't need to transmit a bias signal (P4) to the microphone.
2) The C12VR shows series heaters, which is why it says you need a 12.6V heater supply.
3) You really can't measure the output impedance of the PSU in that way, so it's hard to make sense of your 900K reading.
4) The C12VR uses the same tube at the same voltage, so the 180K resistor should be fine.
5) The polarization voltage goes to the top node (pin 3) on your schematic, and the B+ goes to the pin 5 node.

The moral of this story: you won't be able to get both the stock Apex460 and the C12VR working simultaneously on this design, due to the different heater voltages that are needed with each microphone, unless you re-wire your Apex460 to use series heaters (instead of parallel), or you wire your C12VR to parallel the heaters (instead of series).

 

[sl]

Hi Matador,

What value should the initial set up resistor be for an M49 with the AC701k tube? I was able to trim P5 to output 4V using 180K as Chunger did for the C12 example in this thread but do not want to take any chances.

Thanks,
Steve

 

[Matador]

The AC701 heater is 4V @100mA, so the resistor should be 4/0.1 = 40 ohms, and rated at 0.4W minimum.

Since this is a strange value, I would string four, 10 ohm resistors in series, each of which should be 1/4 W rated.  You should be able to run these all day like this for testing.

 

[mike]

for the C12 build - is the heater measurement supposed to be between heater and ground, or heater and heater - ?
I'm getting almost no dc voltage between heater and ground (like .005vdc) , but I get within the range expected between heater and heater -

is this normal?