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

[RuudNL]

I don't see a R15 in the schematic, only a R5.
Yes, that is the output of the 7812 regulator 'lifted' about 0.6 V. by D11 to give an output of about 12.6 V.
I suppose the input voltage of the regulator is way too high for a 5V output.
You can change the zener diodes to obtain a lower +HT voltage.
Keep in mind that we are dealing here with 'analog equipment', it is not a computer!
So 103 V is fine, but 108 V is also fine! (Usually +/- 5% is more than acceptable.)

 

[Papa Tango Charly]

Thanks Ruud much appreciated
The Apex 460 PSU schematic is incorrect R15 is 20Ohm you can check the picture of the circuit at the end of this post

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

Here is the sketch of the Tbone PSU Sct 2000 Heater section area and a picture of the circuit Heater section
I have checked R15 in a resistor color code calculator.
The color indicates 2Ohm 5% and not 2KOhm

The last time I checked the radiator voltage on the Tbone Sct 2000, the voltage was 6 V.
Is there anyway to drop 1V on the heater section based on these new informations.

FR107 is -1000v-1A-1.2V

Thanks to all of you.

Pictures down there...

 

[Khron]

Yeah, that SCT2000 PSU schematic has almost nothing to do with the Apex 460 PSU schematic. Apples, meet oranges...

 

[Papa Tango Charly]

Yep! I would like a answer to my question please,
is there anyway to drop 1V on the heater section? based on these new informations?

 

[Khron]

First of all, MEASURE what voltage you have ahead of the 7806 regulator, right now. You should be able to measure that across the diodes (between the grounded end of D9, and the cathode / band-end of D7).

THEN we can figure out what sort of power that regulator needs to burn off, and if changing that to a 7805 would still stay within sane power dissipation limits.

 

[Papa Tango Charly]

Thank you Khron
Unfortunately i don't have the PSU with me, I will keep posted as soon i can, until next episode.
Yours Sincerly

 

[mjmajilton]

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

Yes. Replace the two 68 volt zeners with 2 zeners adding up to 105. Replace the 7806 with a 7805 and replace to diode on the center pin with a jumper.

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 schematic is wrong. It's a 7806 to begin with. Use a 7805 and junper out the diode.

 

[Papa Tango Charly]

Great Thank you very much mjmajiton
Yes you are right i changed it. Thanks for that too
Sincerely Yours
This section mentions some of the features and specifications of the 7806 IC.

7806 Regulator Features​

1. Input Voltage range: 8V to 25V
2. Output Voltage: 5.75V(min) - 6.25V(max)
3. Output Current: 1A
4. Peak current: 2.2A
5. Operating Temperature : 0 to +125 C
6. Polarity: Positive

7805 Regulator Features​

• 5V Positive Voltage Regulator
• Minimum Input Voltage is 7V
• Maximum Input Voltage is 25V
• Operating current(IQ) is 5mA
• Internal Thermal Overload and Short circuit current limiting protection is available.
• Junction Temperature maximum 125 degree Celsius
• Available in TO-220 and KTE package