Pearl Two

[PierreQuiRoule]

Rich -

I'm wondering if by any chance all is fine and what we observe is a side-effect of using 2.2k instead of real Q2.

You could try this now:
1) Remove 2.2k.
2) Install Q2.
3) Verify that there is a piece of wire (short-circuit) in lieu of R15.
4) Adjust P1 so you get close to 0 volt on R10.
5) Re-measure the voltages across R6, across R28, and across R29.

Good luck .

[richluvsound]

Checking P channel ZVP 3310a

I have - on C and I get OL on gate and .6V on E .... Yes , I'm being very careful not to short or touch leads with my fingers

I'm using the guide ZM was kind enough to supply , but would like to know if I'm understanding correctly just for confidence ...

Thanks All , Rich

[nar]

Get in in there and see how it behaves !

nAr

[richluvsound]

Originally Posted by PierreQuiRoule

Rich -

I'm wondering if by any chance all is fine and what we observe is a side-effect of using 2.2k instead of real Q2.

You could try this now:
1) Remove 2.2k.
2) Install Q2.
3) Verify that there is a piece of wire (short-circuit) in lieu of R15.
4) Adjust P1 so you get close to 0 volt on R10.
5) Re-measure the voltages across R6, across R28, and across R29.

Good luck .

1) ZVP In

C=23.99 V
B=20.47V
E=-11.51

Bottom of R10 is solid 0V

R6 = -3.52v
R28= 1.34
R29=1.31

[nar]

Originally Posted by richluvsound

1) ZVP In

C=23.99 V
B=20.47V
E=-11.51

By E do you mean Drain pin ? The one who's connected to output cap. The Drain of Q3 should be near Ground level ... ???

If you refer to schematic, ZVP has voltage gain and output taken at the Drain (low point of Q2 in schematic.) If I assume C for you is Source, V+rail, 23,99V looks OK. If B is Gate, then you have 3,52V between Gate and Source. The mosfet is likely to start conducting or already doing it. If your E point refers to Drain of mosfet, then it stands way to low, should be at Ground level, and P1 should permit you to adjust Drain (out) close to zero volts.

Originally Posted by richluvsound

Bottom of R10 is solid 0V

Ok, it's well connected then

Originally Posted by richluvsound

R6 = -3.52v
R28= 1.34
R29=1.31

I assume those are direct resistor measurements, not against Ground. In that case, you run about 13 mA in ZVP3310, and 2,69 mA through the diff. pair. Your R6 direct measure indicates that you run about 2,34mA in Q4. It leaves only 2,69 - 2,34 = 0,35 mA only for Q5. There's likely a problem here. Diff pair currents should be equally shared.

P1 should be set midpoint again before firing up. Mostly to get the voltage drain of Q4 in a convenient place for driving ZVP gate. P1 permits finetuning of output close to zero.

Last thing, have you removed C7 ? I don't remember.

Best,

nAr

[richluvsound]

Originally Posted by nar

By E do you mean Drain pin ? The one who's connected to output cap. The Drain of Q3 should be near Ground level ... ???

If you refer to schematic, ZVP has voltage gain and output taken at the Drain (low point of Q2 in schematic.) If I assume C for you is Source, V+rail, 23,99V looks OK. If B is Gate, then you have 3,52V between Gate and Source. The mosfet is likely to start conducting or already doing it. If your E point refers to Drain of mosfet, then it stands way to low, should be at Ground level, and P1 should permit you to adjust Drain (out) close to zero volts.


Ok, it's well connected then


I assume those are direct resistor measurements, not against Ground. In that case, you run about 13 mA in ZVP3310, and 2,69 mA through the diff. pair. Your R6 direct measure indicates that you run about 2,34mA in Q4. It leaves only 2,69 - 2,34 = 0,35 mA only for Q5. There's likely a problem here. Diff pair currents should be equally shared.

P1 should be set midpoint again before firing up. Mostly to get the voltage drain of Q4 in a convenient place for driving ZVP gate. P1 permits finetuning of output close to zero.

Last thing, have you removed C7 ? I don't remember.

Best,

nAr

C7 not in the board

C=S
B=G
E=D

Sorry , Its a bit better than T,M,B

P1 pin =+/- 100 mV

Q5 Gate = 3.6 mV
Q4 Gate = 22.4 mV

[nar]

Originally Posted by richluvsound

C7 not in the board

C=S
B=G
E=D

Sorry , Its a bit better than T,M,B

P1 pin =+/- 100 mV

Q5 Gate = 3.6 mV
Q4 Gate = 22.4 mV

If Q5 gate is at 3,6 mV, then you should have zero volt on the pin said where to set voltage to zero volt in Pearl II manual.

Is R16 in place and jumper on R15 ?

What do you pin by P1 pin ? is it a reading on one of P1 pins, or the point on the board where it says to set P1 for 0V ?

Best,

nAr

[exojam]

I apologize if this is a simple question but does anyone know of a substitute for the LM7924CT? Both Mouser and Digikey show it as obsolete. Thanks.

James

[exojam]

found the answer in post 555. Sorry.

James

[richluvsound]

Hi nAr,

just got home and turned it . P1 21.06 v but is moving down in voltage into the 10v range ? R16 is in place and there is a jumper on R15 .

P1 is the 0v set pin ....

R