Simplistic NJFET RIAA

[vgeorge]

What is this resistor that I think I see is soldered to the dc input?

 

[skouliki]

If you mean that 100r red PRP resistor its connected to the 2x33r2 resistors forming r1x. Suggested by salas to reduce value from 16.6 ohms to 15ohms for troubleshooting procedure

 

[vgeorge]

Ok, Thought that it was parallel to the DC input.
Are you sure that 9610 is not damaged?

 

[skouliki]

Well thats what i have been thinking, psu seems fine, so irf9610 must be damaged somehow. I remember i took care not to overheat it but ....
Anyway i'll go buy 2 new irf9610 and see what happens

 

[Salas]

Use metal screws this time.

 

[vgeorge]

You could lift it from the board and check it first. They don' t get easily burned from overheating.

 

[Salas]

And a couple of new 100nF 63-100V MKT C3x

 

[Salas]

You could lift it from the board and check it first. They don' t get easily burned from overheating.

Maybe static, but on both channels is weird. Beyond being bought mishandled as a batch, difficult.

 

[Salas]

R2x,R4x confirm 120R.

 

[nezbleu]

I think you should also measure voltages on all 3 pins of Q2x and Q1x, If you have 49V at the "top" of D2x, can you measure voltage all along that string to the drain of Q2x?

 

[Salas]

I think you should also measure voltages on all 3 pins of Q2x and Q1x, If you have 49V at the "top" of D2x, can you measure voltage all along that string to the drain of Q2x?

In case his new 9610s won't make good then the puzzle escalates.

Not even in the hundreds of BIB regs we have had something like that before. Plus his photos show a clean construction with no wrong orientations.

 

[analog_sa]

Much as i feared things went ugly and heavy. As they usually do with my builds

Added a couple of 8H chokes. And a couple more electrolytic caps. 3 ways of hooking the chokes up: 8H, 36ohms or 2H 9ohms, or in common mode. Lots more listening to do.

 

[Salas]

Interesting experiments to many builders. Let us know your evaluations.

P.S. Maybe you could twist some cables in the CLC to reduce their loop area?

 

[skouliki]

I can confirm r2x r4x are 121ohms.
Couldnt find irf9610 in 2 stores i went today so the search will continue tomorrow.
I also found that thread here in the forum which got me worried that maybe my cheap soldering iron might have fried the FET

http://www.diyaudio.com/forums/pass-labs/126130-careful-about-irf9610.html

 

[Salas]

Did you try Radio Katouma? If you will not find any MOSFETS in the end bring it to my place in the weekend since you are a fellow Athenian. I have a few left 9610s I think and my iron is an ESD safe Metcal. Keep the old ones, I want to check them on the DCA tracer to see if they were really dead out of curiosity. We can test the boards off a current limited bench PSU against your own raw PSU in case there is something wrong with it that we could find as well. So bring the whole shebang over.

If you will find MOSFETS, try first, for the sweet revenge you could beat that Murphy geezer on your own.

 

[skouliki]

Salas thank you very much for the invitation and the support. Deeply appreciated!

I went to Fanos and Markidis today and both were out irf9610, so i guess Katoumas and Venieris are the next stops tomorrow. If both of them are out as well, i will pay you a visit

Thanks again

 

[alexkosha]

Interesting experiments to many builders. Let us know your evaluations.

P.S. Maybe you could twist some cables in the CLC to reduce their loop area?

What is the nominal current rating (mA) would you recommend for chokes in Raw PSU for our Folded?

Also, I assume it should be concern about voltage drop.
So, for classic CLC it should be about : 1.4v+0.9v+1.4v= 3.7V
Theoretically, if I have 52v out from my rectifier, then final V out of Raw DC equipped with Pi should be equal to 48.3v. Right?
Thank you.

 

[vgeorge]

The folded draws about 110mA, so choke should be higher than this.
150 to 200 mA should be fine.
Voltage drop is depends from choke' s DCR.
I use RCLC to drop my voltage a bit, as I also have the same voltage as you after rectification.

 

[skouliki]

So i went today and got me the irf9610's.
Replaced the old ones and............. IT WORKS !!
Well i dont know if it actually works properly yet but at least it lights up.

 

[vgeorge]

Very nice! There are not many things that can wrong there.
What voltage you have on R1X?