Fisher 800C FM Stereo problem

[Glowin Plates]

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]

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.

 

[SHiFTY]

Glad you fixed it

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

 

[Ciscokid]

Hi,

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

Regards,
ck

 

[Glowin Plates]

Which Tube

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

 

[Ciscokid]

Thanks,

Will pull my 500 out and check it out..

Regards,
ck