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Old 5th July 2012, 04:47 PM   #1571
nar is offline nar
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Quote:
Originally Posted by Siberia View Post
Across R28, R29 I read 1.1V. Changing Q3 didn't help. What's the practice, if the solder looks OK, but there surely must be trouble somewhere? Desoldering, soldering action on cascode section?
This seems perfect values for R28 R29 ... 2nd stage has proper biaising it seems

nAr
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Old 5th July 2012, 05:10 PM   #1572
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Removed the blob. Desoldered Q1, and that place between too pins looks supicious. I tried to clean, as much as possible to show.

http://i47.tinypic.com/mvg5f7.jpg

Can there be short going on? I think the "line" should be separating two pads, as far as I can see on the other board. How can I clean it properly? I'm afraid to use blade here, when not knowing what is underneath.
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Old 6th July 2012, 09:01 AM   #1573
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Quote:
Originally Posted by Siberia View Post
Removed the blob. Desoldered Q1, and that place between too pins looks supicious. I tried to clean, as much as possible to show.

http://i47.tinypic.com/mvg5f7.jpg

Can there be short going on? I think the "line" should be separating two pads, as far as I can see on the other board. How can I clean it properly? I'm afraid to use blade here, when not knowing what is underneath.
I don't think there is short here. Work seems nicely done except some component leads not cut short enough sometimes maybe Not a big deal though.

I would like to help more, but my box for Pearl is closed and I can't go and see reference voltages. I'l trying to get an annotated sheet with voltages, I had it somewhere but I can't find it for now maybe it is attached to the thread

Best,

nAr

EDIT : found ... attached

Compare to your voltages and debug what is faulty.
As I said 8V - 10V on the jfet drains Q6 - Q9 is fine for biaising. For this, first the sub regulator Q1 and the cascode Q3 must behave correctly.

I had a 8,93V reading on my boards, whilst author of pdf finds 9,4V. Both values are within OK range.

If Emiter of Q3 is 9,4V, then Base must be 10V or so. Collector of Q3 is about 10V1, the cascode is roughly polarized to half the supply rail (a little less, in fact half the Emiter voltage of subregulator Q1).
Emiter of Q1 about 20,2V so Q1 Base is about 20,8V. 24 - 20,8 = 3,2V on R5, which gives 3,2/1500= 0,00213333 A so about 2,13 mA current.

Attached Files
File Type: pdf Pearl2Votages.pdf (45.9 KB, 75 views)
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Last edited by nar; 6th July 2012 at 09:15 AM. Reason: found attachement
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Old 6th July 2012, 09:35 AM   #1574
Siberia is offline Siberia  Lithuania
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Thank you, AnaŽl. You, guys, are already a big help. Yes, I check measurements with Wayne's ones. Yesterday night I've changed Q1 and it fixed some of voltages for sure. New Q1 on other board has been installed just right now. I'm rewiring boards to have some "ordnung" now.

It's a national day off here. That helps a lot. Will I celebrate our kings day with some Pearl music, only ancient gods can tell.
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Old 6th July 2012, 10:06 AM   #1575
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Hope you'll get it runnin' soon

nAr
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Old 6th July 2012, 11:24 AM   #1576
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Quote:
Originally Posted by nar View Post
I don't think there is short here. Work seems nicely done except some component leads not cut short enough sometimes maybe Not a big deal though.

I would like to help more, but my box for Pearl is closed and I can't go and see reference voltages. I'l trying to get an annotated sheet with voltages, I had it somewhere but I can't find it for now maybe it is attached to the thread

Best,

nAr

EDIT : found ... attached

Compare to your voltages and debug what is faulty.
As I said 8V - 10V on the jfet drains Q6 - Q9 is fine for biaising. For this, first the sub regulator Q1 and the cascode Q3 must behave correctly.

I had a 8,93V reading on my boards, whilst author of pdf finds 9,4V. Both values are within OK range.

If Emiter of Q3 is 9,4V, then Base must be 10V or so. Collector of Q3 is about 10V1, the cascode is roughly polarized to half the supply rail (a little less, in fact half the Emiter voltage of subregulator Q1).
Emiter of Q1 about 20,2V so Q1 Base is about 20,8V. 24 - 20,8 = 3,2V on R5, which gives 3,2/1500= 0,00213333 A so about 2,13 mA current.

Mind the error; -26,2V; in the voltage written taken at node of R25 & R27.

Since Emiters are at about -23V, the Bases of bipolars should be standing around -22,4V. This voltage is seen on R25 referenced to Ground, or a current of about 4,71mA through R35 (and also through red led, assuming 1,6V (1V R + 0,6V BE junction) direct voltage for the led @ said current).

Best,

nAr
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Old 7th July 2012, 08:53 AM   #1577
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Thanks for detailing and pointing it out. I'm using this corrected sheet:

http://www.diyaudio.com/forums/attac...l2votages1.pdf

I've left home for home town and celebration. Just after replacing Q1, I only had time for Q1 and Q3 measurements:

Q1
C 24V; 24V;
B 20.7V; 20.7V
E 20V; 20V;

Q3
C 06.7V; 06.7V
B 07.3V; 07.3V
E 06.7V; 06.7V

Getting back to it soon.
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Old 7th July 2012, 09:37 AM   #1578
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Sorry, I was off too try this last update to my posts ...

nAr


Quote:
Originally Posted by Siberia View Post
Thanks for detailing and pointing it out. I'm using this corrected sheet:

http://www.diyaudio.com/forums/attac...l2votages1.pdf

I've left home for home town and celebration. Just after replacing Q1, I only had time for Q1 and Q3 measurements:

Q1
C 24V; 24V;
B 20.7V; 20.7V
E 20V; 20V;

Q3
C 06.7V; 06.7V
B 07.3V; 07.3V
E 06.7V; 06.7V

Getting back to it soon.
Yes, seems definitely better. Q1 seems to behave perfectly. Voltage on Collector, Base and Emiter of Q3 still seem off.
My friend PierreQuiRoule had the same problem if I recall.
That can be tweaked by modding a R value ...

EDIT : Done. Can you try changing R9 for 333 ohms or so, and report Q3 voltages again.
If you don't have a 330 or 333 ohm ready, just solder a 1k in parallel of existing 499


Best,

nAr
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Old 7th July 2012, 10:35 AM   #1579
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Alright! Just about time I was heading to search for a Pierres prob, it's already served on the plate. You are a help gem. Thanks a lot.

I'm on my way back. Will report, after putting my hands on it.
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Old 7th July 2012, 11:09 AM   #1580
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Quote:
Originally Posted by Siberia View Post
Alright! Just about time I was heading to search for a Pierres prob, it's already served on the plate. You are a help gem. Thanks a lot.

I'm on my way back. Will report, after putting my hands on it.
Moderator should erase my post 1578.
Please refer to post 1579 for trying something valuable

Best,

nAr
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