Pearl Two

[studeb]

Originally Posted by 6L6

it's a good guess that Q2 (the ZVP3310) is inoperative. Rich saying that he replaced Q2 with a new one and the measurements are basically the same..

Could they both be bad?
Could Rich test the one he removed?

[richluvsound]

If Rich knew how .....my meter has that facility ,but I have never used it.

I'm willing to try if someone could outline the process in rookie lingo

Rich

[studeb]

Gate-Source is listed as +/-20V
i think you are way over that close to 40V

[nar]

Bear in mind that unlike jfets, those ZVP are static sensitive devices. They are easily ruined ...
Caution when handling out of protective bag (don't touch the leads, or touch then 3 pins at the same time) and solder with care. Pot shoud also be mid-position prior to re-power the board again. Otherwise migh get problem with VGSmax

Best,

nAr

[Zen Mod]

Originally Posted by Zen Mod

programmed current for positive shunt reg : 60mA

programmed current for negative shunt reg : 30mA

per channel

back'o'napkin calc of exact Iq , per channel :
positive leg : 4 x 5mA + 3mA + 2 x 1mA +10mA= 34mA
negative leg : 2mA + 4,6mA + 10mA = 16,6mA

edit : presuming that each input Jfet is in 5mA ballpark

this post of me is , well , mix-up

I was reading thread about X-ONO current consumption , when Wayne conveniently posted schematic ....... so it was easy to answer .
I just didn't got that completely different thread is in question ...

(who knows - maybe someone will need that data )

[richluvsound]

Hi nAr ,



I used ceramic tweezers to handle the ZVP ... I didn't touch it with my fingers . Is there a way I can power up the board and test the voltage presented to Q2 ? .... is this what Wayne was suggesting to 6L6 in using 2.2k resistor across source and drain ?

I'm actually starting to enjoy this process of fault finding ,rather than getting frustrated

Rich

[6L6]

Originally Posted by richluvsound

Is there a way I can power up the board and test the voltage presented to Q2 ? .... is this what Wayne was suggesting in using 2.2k resistor across source and drain ?

Yes, that's it exactly. The resistor will present a similar current to the rest of the circuit in lieu of the active device (ZVP3310)

[richluvsound]

Morning 6 ... great , BTW I have 1k x 2 100r x2 will work better .

I have measured the other board and my VDC @ R10 is 2.3 VDC ...


Rich

[6L6]

Originally Posted by richluvsound

I have measured the other board and my VDC @ R10 is 2.3 VDC ...

Yes, that's not ideal, but what about all the other readings?

[6L6]

An update to Rich's project --

We just had a Skype conversation and have found a couple of things.

Does the term RTFM translate into 'net English? It means Read The Fu*k!ng Manual... Rich and I both failed to do so.

In the Pearl 2 article, Wayne clearly says that R15 is normally a jumper. Rich had it open, and when looking at my boards, so do I. That has been fixed. Having the jumper in place has changed the readings around Q2.

Here are the abnormal readings on Rich's 'left' board.

Q3 1.2v base/ .49 collector/ .46 emitter
R24 (or the source of Q9) .1v
R13 1.33v
Q2 +21.0v gate/ +23.9v drain/ +20.45 drain (Look! It's positive!)

There is some DC fluctuation across the output. The input is open, not shorted.

The + and - rails are good
The voltages on the input stage capacitance multiplier is good (R9 20.0v)
All the readings on the output stage current sources are good.