Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

This could be caused by a number of things. A short between the drivers and
the speakers could be bleeding current equally between the two. It could be
also on the input side. The switch itself could be shorting the two feeds
together. You'd need to open it up and test the signal path to find shorts.
Good luck if there're capacitors in the line...

--

____________________________________

Brandon Anderson
Lighting, Sound, and Video

http://www.bdanderson.com/


"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

This could be caused by a number of things. A short between the drivers and
the speakers could be bleeding current equally between the two. It could be
also on the input side. The switch itself could be shorting the two feeds
together. You'd need to open it up and test the signal path to find shorts.
Good luck if there're capacitors in the line...

--

____________________________________

Brandon Anderson
Lighting, Sound, and Video

http://www.bdanderson.com/


"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

This could be caused by a number of things. A short between the drivers and
the speakers could be bleeding current equally between the two. It could be
also on the input side. The switch itself could be shorting the two feeds
together. You'd need to open it up and test the signal path to find shorts.
Good luck if there're capacitors in the line...

--

____________________________________

Brandon Anderson
Lighting, Sound, and Video

http://www.bdanderson.com/


"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

Does the stereo indicator light come on?

"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

Does the stereo indicator light come on?

"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

Does the stereo indicator light come on?

It's not uncommon on older tuners for the VCO adjustment to be a bit off. If
you can identify it, try rocking the adjustment back and forth a bit. When
the Stereo indicator comes on reliably, you're done.

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

It's not uncommon on older tuners for the VCO adjustment to be a bit off. If
you can identify it, try rocking the adjustment back and forth a bit. When
the Stereo indicator comes on reliably, you're done.

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

It's not uncommon on older tuners for the VCO adjustment to be a bit off. If
you can identify it, try rocking the adjustment back and forth a bit. When
the Stereo indicator comes on reliably, you're done.

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Michael Salmons" wrote in message
om...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. It has a mode switch with three positions: mono, hi-blend and
stereo. They are all identically mono EXCEPT in hi-blend, imagining it
as a stereo image, the sound is moved over a bit to the left, but
still with no channel separation.

This, as I stated before, is an older tuner, probably made in the
mid-seventies, all analog. Does this sound like the malfunction of a
certain part that I could replace? Could it be the MPX chip? Or maybe
the mode switch is bad?

Thanks,

Michael Salmons
salmonsm @ missouri . edu

thanks to all replies regarding this problem, I appreciate the input.
Turned out to be the cleaning of adjustments solved it, in particular
one labeled 19k sep. Again, thanks.

Michael Salmons


(Michael Salmons) wrote in message . com...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. snip

thanks to all replies regarding this problem, I appreciate the input.
Turned out to be the cleaning of adjustments solved it, in particular
one labeled 19k sep. Again, thanks.

Michael Salmons


(Michael Salmons) wrote in message . com...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. snip

thanks to all replies regarding this problem, I appreciate the input.
Turned out to be the cleaning of adjustments solved it, in particular
one labeled 19k sep. Again, thanks.

Michael Salmons


(Michael Salmons) wrote in message . com...
Hello,

I've gotten my hands on a very nice older Sony FM tuner (ST-A6B). It
has a few problems but the most troubling is it will only do mono, not
stereo. snip