Fisher 800C FM Stereo problem

Glowin Plates · 6th March 2004, 05:45 PM

I am having a problem with my Fisher 800C in that when in FM stereo filter mode,
the left channel is really attenuated (Quiet).(all stations)
L and R are loud and clear in FM mono mode so I don't think it's anything in the audio section.
I've heard about upgrades to these tuners something to do with old de-emphasis circuitry that is not compatible with modern
broadcast??
Please help.

Glowin Plates · 12th March 2004, 05:01 AM

Wow I can't believe no one responded to this tempting puzzle.
For the benifit of anyone who runs across a similar problem
it turned out to be a (partially)bad 12Ax7.
Swapped the tube and problem was gone.
From now on I will suspect 40 year old tubes first.

SHiFTY · 12th March 2004, 05:24 AM

Glad you fixed it

I think you had a jargon alert in your first post!

Ciscokid · 13th March 2004, 04:45 AM

Hi,

I've a similar problem in my 500B. Which 12ax7 did you swap?

Regards,
ck

Glowin Plates · 2nd April 2004, 04:43 AM

In the MPX section:
It was V102 th one connected to the MPX seperation Pot.
Good Luck.

Ciscokid · 2nd April 2004, 10:46 AM

Thanks,

Will pull my 500 out and check it out..

Regards,
ck

6th March 2004, 05:45 PM	#1
Glowin Plates diyAudio Member Join Date: Feb 2004 Location: Victoria	Fisher 800C FM Stereo problem I am having a problem with my Fisher 800C in that when in FM stereo filter mode, the left channel is really attenuated (Quiet).(all stations) L and R are loud and clear in FM mono mode so I don't think it's anything in the audio section. I've heard about upgrades to these tuners something to do with old de-emphasis circuitry that is not compatible with modern broadcast?? Please help.

12th March 2004, 05:01 AM	#2
Glowin Plates diyAudio Member Join Date: Feb 2004 Location: Victoria	Found the problem Wow I can't believe no one responded to this tempting puzzle. For the benifit of anyone who runs across a similar problem it turned out to be a (partially)bad 12Ax7. Swapped the tube and problem was gone. From now on I will suspect 40 year old tubes first.

2nd April 2004, 04:43 AM	#5
Glowin Plates diyAudio Member Join Date: Feb 2004 Location: Victoria	Which Tube In the MPX section: It was V102 th one connected to the MPX seperation Pot. Good Luck.

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12th March 2004, 05:24 AM	#3
SHiFTY diyAudio Member Join Date: Jul 2002 Location: New Zealand	Glad you fixed it I think you had a jargon alert in your first post!

13th March 2004, 04:45 AM	#4
Ciscokid diyAudio Member Join Date: Sep 2002 Location: Memphis, TN	Hi, I've a similar problem in my 500B. Which 12ax7 did you swap? Regards, ck

2nd April 2004, 10:46 AM	#6
Ciscokid diyAudio Member Join Date: Sep 2002 Location: Memphis, TN	Thanks, Will pull my 500 out and check it out.. Regards, ck

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