ZV7R: Question from beginner

[salam-kaz]

Hello, everyone. I�fm a Japanese beginner DIYer. Could anyone show me how to adjust ZV7R?
(1) What is an initial value of P1, P2 ,P3(10k pot.)
(2) Which pot.(P1, P2 P3) Should I adjust first?

[Alain Dupont]

salam-kaz,

Welcome in the "Zen world!"

0)- Before power-up, set values to maximum

1)- Set P1 to get 20 volts on both output's
2)- Adjust the values of P2/3 by small steps to get 5 volts across Q3
{the current source} and readjust P1

3)- Readjust P2 or P3 to minimize the DC offset
{each output voltage must be as close as possible, a 50mV is correct}

Once hot, about 20/30minutes repeat steps 1.2,3

Without input signal, You must have the same voltage on R8/R9
each seeing about 3.75 amps

PS: If you dont have 10 turns pots or more, do the adjusts by very small steps...

Good luck!

Alain.

[salam-kaz]

Hi, Alain.
Thank you very much for quick reply and kind step by step instruction.
I�fll try as soon as possible.
I have one question. In this instruction, P1 refer to the one for current source, right?

Kaz

[Alain Dupont]

salam-kaz,

NO, it's P3 for the current souce!

Alain.

[Alain Dupont]

salam-kaz,

I see my mistake, thousand excuses!!


0)- Before power-up, set values to maximum

1)- Set P3 to get 20 volts on both output's
2)- Adjust the values of P1/2 by small steps to get 5 volts across Q3
{the current source} and readjust P3

3)- Readjust P1 or P2 to minimize the DC offset
{each output voltage must be as close as possible, a 50mV is correct}

Regards.
Alain.

[Nelson Pass]

I believe that's the first Japanese flag I've seen here,
and welcome.

[salam-kaz]

Hi, Alain and Nelson
Again, thank you very much for kind advice.
I?fm really happy to join this forum.
I hope I can report the result soon.

Kaz

[Babowana]

Originally posted by salam-kaz


(1) What is an initial value of P1, P2 ,P3(10k pot.)
(2) Which pot.(P1, P2 P3) Should I adjust first?

Kaz San,

I also see Japanese flag first time in this forum. Welcome!

I would have initial values of
(1) P1=P2=8K
(2) P3=3K

And, will follow this steps:
(3) Increase P3 until get 30V across R8
(4) Increase P1 a little bit until get 9V at the gate of Q1 referring to the ground
(5) Adjust P2 until see the lowest offset voltage bewteen the two output nodes

By the way, are you using IFRP240 . . . ?

[salam-kaz]

Hi, Babowana san, how do you do?
Thank you very much for the advice.

>By the way, are you using IFRP240 . . . ?

Actually, before buying IRFP240, I am trying on my prototype with FS22SM(Mitsubishi), and 2SK2371(NEC) which I found from scrap(junk?) power supply circuit board. It seems they have close max rate but different output characteristics(Id-Vds).
And today, my first attempt was unsuccessful. Smoke came out. Maybe I should draw a load line and think about more carefully.

>(3) Increase P3 until get 30V across R8

Increase P3 goes to increase Ids of Q3?

Kaz

[Babowana]

Originally posted by salam-kaz


Increase P3 goes to increase Ids of Q3?

Yes, Kaz san.

Sorry about the smoke.
I thought that you were playing with IRFP240.
I just checked datasheet of FS22SM(Mitsubishi), and
found Vgs(th) lower than IRFP240. Please, start with
lower P3 value, e.g. about 1K.

I think you don't need to worry about Q1 and Q2.
Their Vgs will be set according to the Id value (current
source bias) which will be decided by Q3 (current source).
I hope you will use "heat sinks big enough."
Good luck.

I am very intersted in your result . . .