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.
Any ideas?
Do you think there are some inoperative transistors or something else?
Right Board .
I'm tempted to pull ZVP and use the 2.2k to see if everything settles . P1 is acting the idiot and not doing what we want . I got it to 6 VDC and it swung to
-24.39 VDC and no amount of adjustment will move it ?
All the other voltages are pretty much the same as the first test we ran .
At least the aluminium is here so I can crack on with the cases
R
I'm tempted to pull ZVP and use the 2.2k to see if everything settles . P1 is acting the idiot and not doing what we want . I got it to 6 VDC and it swung to
-24.39 VDC and no amount of adjustment will move it ?
All the other voltages are pretty much the same as the first test we ran .
At least the aluminium is here so I can crack on with the cases
R
Clearly it doesn't work as intended.Q3 1.2v base/ .49 collector/ .46 emitter
Q3 is the cascode for 4 paralleled Jfets.
Way too much currentR24 (or the source of Q9) .1v
From those last two points, I would say one to four of the jfets are defective / Q3 is maybe also culprit here
I dunno if the gate should rather be close to Ground potential ???R13 1.33v
Drain should be aroud 0V tooQ2 +21.0v gate/ +23.9v drain/ +20.45 drain (Look! It's positive!)
Try to short inputs and re-read the measure points ...There is some DC fluctuation across the output. The input is open, not shorted.
if still fluctuation at output, then maybe the thing just oscilates. Make sure C7 is out, and C9 in place.
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.
Makes me think in relation to diff. pair gate voltage that maybe those are not working properly. Then issue finds its way at the output.
All I can say for now. is it possible to trace a small input signal and see where it goes out, or finds itself at the output ?
nAr
thanks nAr and 6 ,
i just received all new actives from a friend in California
New Jfets and Regs . I have all new caps if needed .
Perhaps you guys can come up with a way to sort this out between you.
I'm not going to look at it till a plan is made and orders issued
I'm OK with it now , I have learned there is no short cut with this stuff and now I feel more confident reading a schematic its easier to take direction.
I really do appreciated all the help and patience . Having done some teaching myself I do understand it can be a bit frustrating ,but ultimately rewarding .
Rich
i just received all new actives from a friend in California
New Jfets and Regs . I have all new caps if needed .
Perhaps you guys can come up with a way to sort this out between you.
I'm not going to look at it till a plan is made and orders issued
I'm OK with it now , I have learned there is no short cut with this stuff and now I feel more confident reading a schematic its easier to take direction.
I really do appreciated all the help and patience . Having done some teaching myself I do understand it can be a bit frustrating ,but ultimately rewarding .
Rich
Corrected voltages on the schematic. 6L6 pointed out I had a negative voltage exceeding the supply.
Isn't the CE voltage of Q3 too low?
Regards,
George
Hi Gents ,
I have replaced Q3 and inserted 2.2k on the left board .....no change for the better .
Is there someone with more knowledge than me that could me some more voltages around Q3 - I have 2 VDC and need 10 VDC . R 9 is good at 19.99 VDC
and should be 20.2 VDC .
Rich
I have replaced Q3 and inserted 2.2k on the left board .....no change for the better .
Is there someone with more knowledge than me that could me some more voltages around Q3 - I have 2 VDC and need 10 VDC . R 9 is good at 19.99 VDC
and should be 20.2 VDC .
Rich
Hi Gents ,
I have replaced Q3 and inserted 2.2k on the left board .....no change for the better .
Is there someone with more knowledge than me that could me some more voltages around Q3 - I have 2 VDC and need 10 VDC . R 9 is good at 19.99 VDC
and should be 20.2 VDC .
Rich
Q1 is additional filtering for the power supply. From the schematic if you got correct voltage after Q1 then Q3 should work.
Have you double checked resistor values / and / or if they are still good, not open ? I mean R8, R9, R10. I would then check joints arond those / continuity test; and use a new Q3 ZTX450 with only one K170BL on below. You should get 4 times less current approx, but it should work even if lower gain. Can you try this and report if success, and values you get on Jfet drain ?
R11/ R12 values correct ? 6K81 and 909 ohm Check anty shorts to ground plane in that area too
Best,
nAr
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18 V drop across R9 ? fried ?
Probably not, otherwise it wouldn't do such a V drop. A short is maybe after, R8/R10 or R11, or the K170BL has too much current draw for another reason short @ drain or R source maybe ? Or totally open ? Sounds so, seen the V drop you have on R24 (or simili ), you stated 0,1V ; on 10 ohms it does 10 mA ... that is a little high, which is the IDSS of the Jfet you use ???
Best,
nAr
Nar - (and everybody else...)
Just finished another conversation with Rich.
The output stage is disabled, all the transistors have been removed.
The input stage has only one K170BL installed.
There are no shorts that can be found, and the resistors appear to be all correct.
Voltages --
R9 20.3v
Q3 17.6v collector/ 10.4v base/ 9.4 emitter
Q6 9.3 drain/ .05 source
Just finished another conversation with Rich.
The output stage is disabled, all the transistors have been removed.
The input stage has only one K170BL installed.
There are no shorts that can be found, and the resistors appear to be all correct.
Voltages --
R9 20.3v
Q3 17.6v collector/ 10.4v base/ 9.4 emitter
Q6 9.3 drain/ .05 source
Nar - (and everybody else...)
Just finished another conversation with Rich.
The output stage is disabled, all the transistors have been removed.
The input stage has only one K170BL installed.
There are no shorts that can be found, and the resistors appear to be all correct.
Voltages --
R9 20.3v
Q3 17.6v collector/ 10.4v base/ 9.4 emitter
Q6 9.3 drain/ .05 source
Thanks 6K6 Rich, those voltages look fine to me.
Next, use 4 BLs and see how it turns. If readings still fine, then yo ! 2nd stage
Best,
nAr
What about the 17v on the collector of Q3? Will that become better when the rest of the input chain is installed? Or when the output stage is connected?
Dunno. Rich should now try with 4 BLs and post read values.
Mostly 17V, I expect R11 and R12 not to be short to gnd plane.
I can't do any measure on mine for now
Got to get ready to go
Best,
nAr
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