Is it possible to modify a Tbone PSU (Apex 460 PSU) to build Olivier Archut EF800 type of U47 microphone circuit?

[Papa Tango Charly]

If i would like build a version of U47 with a EF800 Olivier Archut EF800 type of U47 microphone circuit.
Is it possible to modify "The Tbone PSU" (as the new version of APEX 460 circuit with a an improved version of the ground plane?
It's a great PSU
Would i need to rework the filtering on the Tbone chinese PSU circuit with a EF800 tube?
If yes... is there a way to drop down the B+ to 105V and H+ to 5,05V?
Thank you all

 

[Spencerleehorton]

Drawing or getting a schematic might be a good place to start

 

[Papa Tango Charly]

I have found This Schematic
Heater = 12,6
B+ = 196V /

If i take away D11 the heater drop to around 6,3V is there a way to drop this tension down to 5,05V?
i don't know if it's possible to drop the tension down B+ to 105v do i need extra filtering for an EF800 tube?

 

[Khron]

If i take away D11 the heater drop to around 6,3V is there a way to drop this tension down to 5,05V?

... And you replace the 7812 regulator with a 7805.

i don't know if it's possible to drop the tension down B+ to 105v do i need extra filtering for an EF800 tube?

Replace the two zeners with a pair of 51v or 56v ones.

 

[Papa Tango Charly]

Great Thank'a lot
yours sincerly

 

[rock soderstrom]

Yes, you can reduce B+ to your desired voltage with larger resistors or by adding another RC filter stage. You also have to adjust the zener diodes, at the moment they clamp the voltage to about 200V. Its good to have additional filtering after the zener diodes. Ohms Law is your friend when calculating resistors.

The heater voltage needs more modification. At the moment the output is 12.6V. If you take out the FR107 diode, it's only 12V, which doesn't help you any.

I would replace the 7812 with a (static) LM317 plus circuitry and additional RC filters. Your heater voltage should be very clean as it is part of the biasing of the tube. A simple exchange to a LM7805 will not be sufficient here IMHO.

some ideas:

 

[Papa Tango Charly]

Thank You

 

[Papa Tango Charly]

Sorry i made a confusion i have made a mod on an other PSU of another brand i had to take D11 to drop the voltage from 6,3 to 6V

The Apex 460 schematic is not the same as the Tbone Sct 2000


The Tbone Sct 2000 mod and the Heater of the PSU is 6V without changing anything.
The B+ voltage is 200V but i have changed the vvoltage to 120v changing D5 an D6 with a 58V and 62V diode
This Tbone PSU worked really well on M49 that a friend build.
I'm a little confuse now.

... And you replace the 7812 regulator with a 7805.



Replace the two zeners with a pair of 51v or 56v ones.

Looking at this circuit could you assure me that this would be the best solution.
It seems like there is some filtering after 7806 isn't it?

Thank You

 

[RuudNL]

After you (only) change the 7812 to a 7805, you have to drop an extra 7 volts (@300 mA?), so that means 2.1 Watt extra to dissipate! I suppose the 7805 will get mad hot!

 

[Papa Tango Charly]

After you (only) change the 7812 to a 7805, you have to drop an extra 7 volts (@300 mA?), so that means 2.1 Watt extra to dissipate! I suppose the 7805 will get mad hot!

The heater voltage on the Tbone STC2000 PSU is 6v not 12V (this schematic isn't valid). The deal is to drop de voltage from 6V to 5,05V not 7V.
Would it be ok to drop 1V and then replaced the front standard diode of the linear regulator with a schotty, to add a voltage of 0.05V?
do you think i could use a 7805 in that condition?

 

[RuudNL]

It will get hotter anyway. Maybe it is an idea to increase the value of the resistor at the input of the regulator, in order to spread the dissipation between the regulator and the resistor.

(I referred to the 7812 because that was the component in the schematic, but apparently you are going to use another power supply.)

 

[Papa Tango Charly]

Thank you Ruud
Good idea
I will use the Tbone StC 2000
https://www.thomann.de/fr/the_tbone_psu_sct_2000.htmHeater 6V and B+ 2000
Can i replace the two zeners with a pair of 51v or 56v ones to drop the B+ at 105V ?
Thank you

 

[Papa Tango Charly]

It will get hotter anyway. Maybe it is an idea to increase the value of the resistor at the input of the regulator, in order to spread the dissipation between the regulator and the resistor.

(I referred to the 7812 because that was the component in the schematic, but apparently you are going to use another power supply.)

Thank you Ruud
Good idea what resitor value should i use ?
I will use the Tbone Stc 2000 the new version of APEX 460
https://www.thomann.de/fr/the_tbone_psu_sct_2000.htmHeater 6V and B+ 2000
Can i replace the two zeners with a pair of 51v or 56v ones to drop the B+ at 105V ?
Thank you

 

[mihi_fuchs]

Hi,

In my hands both - the lm317 as well as lm78xx - gave a noise level which was too high for my taste. I got a quite good explaination here in the forum:
Post in thread 'D-EF47 Tribute To Oliver Archut U47 Build Thread.'
D-EF47 Tribute To Oliver Archut U47 Build Thread.

Thanks again for that to @TLRT for the help and knowledge.

I also ran into that post that i‘d like to give a try, but so far i did not find time. Maybe it is helpful to you:
https://groupdiy.com/threads/u47ef-oliver-archut-version.84508/post-1097400
Hope that helps a bit with the question at hand…
All the best with the built, hope you manage a nice mic.

Best regards,
Michael

 

[rock soderstrom]

Heater 6V and B+ 2000
Can i replace the two zeners with a pair of 51v or 56v ones to drop the B+ at 105V ?
Thank you

Yes, you can reduce B+ to your desired voltage with larger resistors or by adding another RC filter stage. You also have to adjust the zener diodes, at the moment they clamp the voltage to about 200V. Its good to have additional filtering after the zener diodes. Ohms Law is your friend when calculating resistors.

Are the two 10000uf caps before or after the regulator? Can you sketch the schematic for the power supply? At least the heater part?

 

[Papa Tango Charly]

Thank you all
I don’t have the psu with me now but I’m going to grab more details. Thank you again

 

[RuudNL]

The 78xx and LM3xx regulators are known to be noisy.
Usually extra filtering is necessary.

 

[Papa Tango Charly]

I found some picture in my camera of the PSU Tbone SCT2000
Mabye you can get more information buy watching this picture.
Thank you
Yours sincerly

 

[RuudNL]

With a 7805 regulator, I would increase the value of the 2 ohm(?) resistor, to spread the dissipation better between the regulator and the resistor. It depends on the input voltage the regulator receives.
Usually this is pretty high. Most 'Chinese' power supplies use a 9 volts winding for the filament.
After rectification and smoothing this results in about 1.41 x 9 = 12.6 Volts.
You want 5 Volts, so the total dissipation is 12.6 - 5 = 7.6 V * 0.3 A = 2,28 Watt.
With a resistor of 10 ohms (2 Watt) the regulator will get about 9.6 V @ 300 mA.
Resistor dissipation is 0.9 Watt (Use a 2 Watt resistor to stay on the safe side)
Regulator dissipation is 9.6-5 = 4.6 * 0.3 = 1.38 Watt, that is within reasonable limits.
Ooh, and dont forget to short D11, because if you don't do that, you will get 5.6 V output instead of 5.0 (5.1) V!

 

[Papa Tango Charly]

Thank you Ruud for your information

Is it of to replace the two zeners with a pair of 51v or 56v ones. to get 105V
Do i need to make any changes for the heater?


That was one your quote

https://groupdiy.com/threads/apex-460.81244/page-2Most of these Chinese power supplies have an output of about 6.7 Volts for the filament.
This will shorten the life of the tube.
They use a 7806 with a diode connected to the center pin of the 7806, to 'lift' the voltage 0.7 V.
Bridging the diode will bring the output voltage down to 6 Volts.
And of course you will lose a little bit of voltage in the microphone cable, but this will generally be not more than 0.1 Volt. (Unless you use a really bad cable...)

Could you tell me where is the 12,6 output in on the picture of the tbone. is it before R15?
Is it the R15 resistor that i should change?

Thank you
Yours sincerly