Please do some measures again and post. Rails, and other parts.
I assume you talk about led Vref so I also assume you talk about Pearl II
Best,
nAr
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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
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
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After a long skype conversation with Rich and a quick phone call to our esteemed Mr. Colburn, it's a good guess that Q2 (the ZVP3310) is inoperative.
However, as I am sitting here typing this, I got an Email from Rich saying that he replaced Q2 with a new one and the measurements are basically the same...
The rails are fine, at + and- 24v. There is a little low voltage around Q3, 7.9 base / 7.3 collector / 7.2 emitter .
The big problem are the voltages around Q2 -- they are +23 drain / +19v gate / -23.8v source. This is not good, as there should be zero volts (or close) on the source.
Also, the measurements around Q11 are -23v base / -23.8v collector / -23.9v emitter.
However, as I am sitting here typing this, I got an Email from Rich saying that he replaced Q2 with a new one and the measurements are basically the same...
The rails are fine, at + and- 24v. There is a little low voltage around Q3, 7.9 base / 7.3 collector / 7.2 emitter .
The big problem are the voltages around Q2 -- they are +23 drain / +19v gate / -23.8v source. This is not good, as there should be zero volts (or close) on the source.
Also, the measurements around Q11 are -23v base / -23.8v collector / -23.9v emitter.
I didn't ask if C9 is installed.
The PSU is grounded to the mains as shown in the article, through the bridge. The Pearl circuit board is not in a case, nor are the signal leads hooked up.
Would oscillation cause the negative rail to appear at the source of Q2?
Should the input be grounded for testing? And/or the output?
The PSU is grounded to the mains as shown in the article, through the bridge. The Pearl circuit board is not in a case, nor are the signal leads hooked up.
Would oscillation cause the negative rail to appear at the source of Q2?
Should the input be grounded for testing? And/or the output?
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
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
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 )
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
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
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)
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?
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.
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.