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Old 18th December 2011, 10:43 PM   #1271
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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 .
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Old 19th December 2011, 09:38 AM   #1272
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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
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Old 19th December 2011, 09:50 AM   #1273
nar is offline nar
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Get in in there and see how it behaves !

nAr
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Old 19th December 2011, 11:18 AM   #1274
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Quote:
Originally Posted by PierreQuiRoule View Post
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
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Old 19th December 2011, 06:06 PM   #1275
nar is offline nar
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Quote:
Originally Posted by richluvsound View Post
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.

Quote:
Originally Posted by richluvsound View Post
Bottom of R10 is solid 0V
Ok, it's well connected then

Quote:
Originally Posted by richluvsound View Post
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
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Old 19th December 2011, 06:50 PM   #1276
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Quote:
Originally Posted by nar View Post
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

Last edited by richluvsound; 19th December 2011 at 06:52 PM.
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Old 19th December 2011, 07:02 PM   #1277
nar is offline nar
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Quote:
Originally Posted by richluvsound View Post
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
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"Just 'cause they can't hear or sense it themselves doesn't mean you can't !" Allen Wright Allen was right ...

Last edited by nar; 19th December 2011 at 07:05 PM.
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Old 19th December 2011, 07:48 PM   #1278
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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
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Old 19th December 2011, 08:44 PM   #1279
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found the answer in post 555. Sorry.

James
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Old 19th December 2011, 11:48 PM   #1280
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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
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