Oscillating CJ PV-5

batsong · 21st April 2010, 08:29 AM

Hi. I think this is my first post.
I am having a bad problem with a Conrad Johnson PV-5.

It started to rustle badly in the right channel, so started wiggling and swapping tubes, and moving the pots and selectors around to try to fix/find the source of the noise. Then the rustling got louder and spread to the other channel. I then noticed that the 5751 and the 5965 were switched in the phono stage and that the phono stage would oscillate badly when I turned up the volume. I tried changing some of the diodes on the power supply, as I have had these go bad before. When I turned the preamp on again,a bad hum had joined the party, so I changed the diodes back. No change.

Now I have a humming, badly oscillating preamp that rustles.

Any ideas?

SGregory · 21st April 2010, 12:49 PM

Have you changed your caps? That is what happened to mine.

batsong · 21st April 2010, 07:13 PM

Thanks,
No caps have been changed. Maybe I'll start trying to isolate the culprit(s). What kind did you use? I see that Jantzens might be a good deal.
-Gabe

SGregory · 21st April 2010, 07:49 PM

I replaced them years ago b4 I was really into DIY. They came from CJ. They were the electrolytics in the PS

batsong · 22nd April 2010, 12:51 AM

The hum was a PS diode, and it looks like the restof the trouble is caused by the relay switch that lets the preamp warm up before starts operating. Is there a way to bypass this relay? It has been cleaned before, and even still it only worked in one channel. I would like to get rid of it.
Thanks

21st April 2010, 08:29 AM	#1
batsong diyAudio Member Join Date: Jan 2008 Location: Oregon	Oscillating CJ PV-5 Hi. I think this is my first post. I am having a bad problem with a Conrad Johnson PV-5. It started to rustle badly in the right channel, so started wiggling and swapping tubes, and moving the pots and selectors around to try to fix/find the source of the noise. Then the rustling got louder and spread to the other channel. I then noticed that the 5751 and the 5965 were switched in the phono stage and that the phono stage would oscillate badly when I turned up the volume. I tried changing some of the diodes on the power supply, as I have had these go bad before. When I turned the preamp on again,a bad hum had joined the party, so I changed the diodes back. No change. Now I have a humming, badly oscillating preamp that rustles. Any ideas?

21st April 2010, 12:49 PM	#2
SGregory Tubie Noobie diyAudio Member Join Date: Apr 2003 Location: Southern Tier NY	Have you changed your caps? That is what happened to mine. __________________ Living Life Doing the Waltz in 4/4 meter.

21st April 2010, 07:49 PM	#4
SGregory Tubie Noobie diyAudio Member Join Date: Apr 2003 Location: Southern Tier NY	I replaced them years ago b4 I was really into DIY. They came from CJ. They were the electrolytics in the PS __________________ Living Life Doing the Waltz in 4/4 meter.

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21st April 2010, 07:13 PM	#3
batsong diyAudio Member Join Date: Jan 2008 Location: Oregon	Thanks, No caps have been changed. Maybe I'll start trying to isolate the culprit(s). What kind did you use? I see that Jantzens might be a good deal. -Gabe

22nd April 2010, 12:51 AM	#5
batsong diyAudio Member Join Date: Jan 2008 Location: Oregon	The hum was a PS diode, and it looks like the restof the trouble is caused by the relay switch that lets the preamp warm up before starts operating. Is there a way to bypass this relay? It has been cleaned before, and even still it only worked in one channel. I would like to get rid of it. Thanks

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