pearl, q4 no voltage

noelectrix · 20th January 2009, 12:58 PM

unfortunately one channel of my pearl phono stage stopped working and needs some help. First aid indication:

No voltage on Q4 (the ztx 450) next to the 2sk 389. There is a "control point" were I should measure 13,8 V or so. Any hint what that points to?

help is highly appreciated
stefan

noelectrix · 20th January 2009, 01:29 PM

It´s not exatly zero, Imeasured 750 mV.
stefan

cviller · 21st January 2009, 04:30 PM

What is the voltage on either pin of R8 in reference to gnd?

You can measure the 13.6V on the emitter of Q4. The emitter is the one which is not the middle pin and not connected to R14...

noelectrix · 24th January 2009, 06:37 PM

hi cvi,
late answer.
on R8 i measured 28,1 and 28,6 to gnd.
the same points at the working channel give 28,4 and 28,7. So seems to be the same.
stefan

cviller · 24th January 2009, 08:54 PM

My best guess is that you have burned the 2sk389 (not your fault, but a lot of people have had this problem).

If you don't think that is the problem. Please take the schematics and put all your measurements on the schematics (you can do this is in paint), then I might be able to point you to the problem.

noelectrix · 24th January 2009, 09:25 PM

hey cviller, that is veery kind of you. When Leela finished, I´ll also have a look at the schematics and report

[IMG]

[/IMG]

noelectrix · 24th January 2009, 09:27 PM

I heard that it is wise to split the source resistors. If i can find another 2sk 389 i´d try it this way.
stefan

cviller · 24th January 2009, 09:51 PM

You can easily use two 2sk170, but you'll have to match them (idss).

Quote:

Here's to us poor schmoes, working for the man. Although she is a hot, sexy female man.

noelectrix · 24th January 2009, 10:08 PM

yes, of course, i read that somewhere with the sk 170 substitution. and i got some here

but how to do that will be my tomorrow´s research. huhu, i dip my feet n electronics

tnx,
stefan

noelectrix · 26th January 2009, 02:37 PM

cviller, thanx again for offering your help.
After a friend of mine also supposed that the double fet is gone, i was offensive and changed it with two 2sk 170. I matched them with a 9V battery and a 10Ohm resistor.
Than i split the source resistors (two 20 Ohms) and everything is fine now. soundstage still in the middle.

When i plugged it in there still was no sound on the left channel, but it turned out that the cable was broken. (but the channel was also

)

tnx
stefan

20th January 2009, 12:58 PM	#1
noelectrix diyAudio Member Join Date: Dec 2006	pearl, q4 no voltage unfortunately one channel of my pearl phono stage stopped working and needs some help. First aid indication: No voltage on Q4 (the ztx 450) next to the 2sk 389. There is a "control point" were I should measure 13,8 V or so. Any hint what that points to? help is highly appreciated stefan

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20th January 2009, 01:29 PM	#2
noelectrix diyAudio Member Join Date: Dec 2006	It´s not exatly zero, Imeasured 750 mV. stefan

21st January 2009, 04:30 PM	#3
cviller diyAudio Member Join Date: Dec 2005 Location: Copenhagen Blog Entries: 2	What is the voltage on either pin of R8 in reference to gnd? You can measure the 13.6V on the emitter of Q4. The emitter is the one which is not the middle pin and not connected to R14...

24th January 2009, 06:37 PM	#4
noelectrix diyAudio Member Join Date: Dec 2006	hi cvi, late answer. on R8 i measured 28,1 and 28,6 to gnd. the same points at the working channel give 28,4 and 28,7. So seems to be the same. stefan

24th January 2009, 08:54 PM	#5
cviller diyAudio Member Join Date: Dec 2005 Location: Copenhagen Blog Entries: 2	My best guess is that you have burned the 2sk389 (not your fault, but a lot of people have had this problem). If you don't think that is the problem. Please take the schematics and put all your measurements on the schematics (you can do this is in paint), then I might be able to point you to the problem.

24th January 2009, 09:25 PM	#6
noelectrix diyAudio Member Join Date: Dec 2006	hey cviller, that is veery kind of you. When Leela finished, I´ll also have a look at the schematics and report [IMG] [/IMG]

24th January 2009, 09:27 PM	#7
noelectrix diyAudio Member Join Date: Dec 2006	I heard that it is wise to split the source resistors. If i can find another 2sk 389 i´d try it this way. stefan

24th January 2009, 10:08 PM	#9
noelectrix diyAudio Member Join Date: Dec 2006	yes, of course, i read that somewhere with the sk 170 substitution. and i got some here but how to do that will be my tomorrow´s research. huhu, i dip my feet n electronics tnx, stefan

26th January 2009, 02:37 PM	#10
noelectrix diyAudio Member Join Date: Dec 2006	cviller, thanx again for offering your help. After a friend of mine also supposed that the double fet is gone, i was offensive and changed it with two 2sk 170. I matched them with a 9V battery and a 10Ohm resistor. Than i split the source resistors (two 20 Ohms) and everything is fine now. soundstage still in the middle. When i plugged it in there still was no sound on the left channel, but it turned out that the cable was broken. (but the channel was also ) tnx stefan

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