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Old 13th December 2011, 05:53 PM   #1171
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Quote:
Originally Posted by nar View Post
have you tried R9 mod as Pierre said ? which V on jfet drains now ?

Best,

nAr
Hi nAr,

no I have not tried that ... I think I need to concede defeat here and ask for direct intervention . 6 and I must have spent 15 hours over the past 2 weeks trying to get this thing to work .

I really need to ask if there is anyone that would be good enough to take a look at these boards for me . I don't have a ton of cash ,but I would be willing to pay someone something for the help .

I can't get the P1 even close to zero . I get nothing ,but a static sound when I test it with a signal .
I don't have scope . I just have too much money in this project to walk away . I don't like quitting ,but I do know I'm out of my depth with this .

F^*&^*^)*( IT . I'm sick of looking at it !

Rich
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Old 13th December 2011, 06:53 PM   #1172
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I would be more than willing to build an enclosure in exchange for time !
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Old 13th December 2011, 07:16 PM   #1173
nar is offline nar
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Quote:
Originally Posted by richluvsound View Post
Hi nAr,

no I have not tried that ... I think I need to concede defeat here and ask for direct intervention . 6 and I must have spent 15 hours over the past 2 weeks trying to get this thing to work .

I really need to ask if there is anyone that would be good enough to take a look at these boards for me . I don't have a ton of cash ,but I would be willing to pay someone something for the help .

I can't get the P1 even close to zero . I get nothing ,but a static sound when I test it with a signal .
I don't have scope . I just have too much money in this project to walk away . I don't like quitting ,but I do know I'm out of my depth with this .

F^*&^*^)*( IT . I'm sick of looking at it !

Rich
Rich

you have to be patient, getting 1st stage working properly without 2nd stage.
In case, remove all active devices of 2nd stage or biasing resistors for 2nd stage
from v+ v- to work on 1st stage alone.

Best,

nAr
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Last edited by nar; 13th December 2011 at 07:18 PM.
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Old 13th December 2011, 07:30 PM   #1174
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Hi nAr, merci !


remove P1 , Q5,Q2, Q10,Q11,Q4 ?

Rich
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Old 13th December 2011, 08:22 PM   #1175
wayne is offline wayne  United States
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If you want to adjust bias on Q3 it is best to adjust R10. R3 is part of the equalization network. I may have suggested the wrong resistor.

power supply voltage can also be dropped with some 5W zeners as part of the CRC filter network. Ten Ohms caps 100 Ohms 39 volt Zener. a little fiddling and this should get you a shunt regulator feeding the 24 regs.
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Old 13th December 2011, 08:37 PM   #1176
nar is offline nar
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Quote:
Originally Posted by richluvsound View Post
Hi nAr, merci !


remove P1 , Q5,Q2, Q10,Q11,Q4 ?

Rich
Yes. And see how 1t stage goes by Pierre suggestion ... 4 fets with 9-10V @drain = target

Best,

nAr
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Old 13th December 2011, 11:06 PM   #1177
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Quote:
Originally Posted by richluvsound View Post
remove P1 , Q5,Q2, Q10,Q11,Q4 ?
Just Q10 and Q11 will do.
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Old 13th December 2011, 11:32 PM   #1178
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Ok, I have P1 and the led in the output stage and just 1 fet ( at the moment in the input )... i'll check the voltages then put the other 3 back in and post the voltage in the morning .

Rich
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Old 14th December 2011, 01:19 AM   #1179
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Originally Posted by wayne View Post
If you want to adjust bias on Q3 it is best to adjust R10. R3 is part of the equalization network. I may have suggested the wrong resistor.
Oh... You mean that the resistor at the collector of Q3 (R9, 499 ohms) plays in the RIAA filter? We don't want to mess with it then!

Got it, I should have lowered the voltage at the base of Q3 through the resistor between its base and ground (R10, 10k).

Am I ever glad I asked
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Old 14th December 2011, 01:25 AM   #1180
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Done. I put R9 back to 499 ohms, and lowered R10 from 10k to 3.22k. This biases Q3 at Vc=5.1 > Vb=4.4 > Ve=3.7.
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