Dead section of FM band on Sansui Stereo Receiver 661

I just found an old discarded Sansui receiver. It works well in all
respects except a large middle section of the AM and FM band don't
receive any stations. A couple of stations on the extreme ends of each
band come in loud and clear, distortion free.

All other aspects of the receiver work fine.

Is there a way that I can fix the tuner section by re-winding coils or
something else I can try that's reasonably inexpensive. I am not an
electronics expert but I am open to any ideas.

Thanks,

Gord

 

[N_Cook]

Do the stations agree with the scale markings? ie someone restringed
wrongly.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[GregS]

In article <81da5108-db5b-4ea1-ab6b-3acc633fa49a@y1g2000pra.googlegroups.com>, "hr(bob) hofmann@att.net" <hrhofmann@att.net> wrote:

On Jan 7, 12:17=A0pm, "N_Cook" <dive...@tcp.co.uk> wrote:
Do the stations agree with the scale markings? ie someone restringed
wrongly.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list onhttp://hom=
e.graffiti.net/diverse:graffiti.net/


What is the tuning mechanism, if it is a moving variable capacitor,
maybe the plates are shorting, that would explain the deadness at the
same points in the dial for both am and fm.

Spider webs and other things will goof up the tunning. I have one in the garage I use,
i have to flip the tunning back and forth a few times before it
will work at the low end on FM. The fact that its both AM and FM
would seem to turn this theory off, but check it out. Does it have
caps ??


greg

 

[DaveM]

<imseakin@yahoo.com> wrote in message
news:45cb41d8-66e5-4f74-9e29-051b7d3dd83b@k36g2000yqe.googlegroups.com...

I just found an old discarded Sansui receiver. It works well in all
respects except a large middle section of the AM and FM band don't
receive any stations. A couple of stations on the extreme ends of each
band come in loud and clear, distortion free.

All other aspects of the receiver work fine.

Is there a way that I can fix the tuner section by re-winding coils or
something else I can try that's reasonably inexpensive. I am not an
electronics expert but I am open to any ideas.

Thanks,

Gord

You don't have to be an Expert in electronics to repair equipment, but you
certainly need a bit of knowledge and understanding of components and circuits.
Rewinding coils is a last resort, and only in the event that you have positively
identified that one is defective.
First, what is your level of knowledge and experience in understanding and
repairing circuits?
What kind of test equipment do you have available? Can you use the equipment
and understand what it's telling you?
At a minimum, you should have a multimeter. A signal generator covering the FM
and/or AM bands would be nice to have, as would a scope. In your situation, the
signal generator and scope would be more useful than a multimeter.
Since the unit works, apparently well, on the ends of the dial, you can probably
rule out everything from the 1st IF through the audio outputs. That leaves the
RF amp, the local oscillator(s) and the mixer(s). Check that the tuning
capacitor plates aren't touching at any point in their travel. If any of the
outside plates are bent outward, don't disturb them; just make sure that the
rest are straight and not touching. Touching plates would explain the symptom
that you described.
You didn't say whether the unit is solid state or tube (valve) construction.
That would be helpful to know. What's the model number of the unit?

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer it gets to the end, the faster
it goes.

 

[hr(bob) hofmann@att.net]

On Jan 7, 12:17 pm, "N_Cook" <dive...@tcp.co.uk> wrote:

Do the stations agree with the scale markings? ie someone restringed
wrongly.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/

What is the tuning mechanism, if it is a moving variable capacitor,
maybe the plates are shorting, that would explain the deadness at the
same points in the dial for both am and fm.

 

[jakdedert]

hr(bob) hofmann@att.net wrote:

On Jan 7, 12:17 pm, "N_Cook" <dive...@tcp.co.uk> wrote:
Do the stations agree with the scale markings? ie someone restringed
wrongly.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/


What is the tuning mechanism, if it is a moving variable capacitor,
maybe the plates are shorting, that would explain the deadness at the
same points in the dial for both am and fm.

That would be my guess as well...shorting could mean bent plates or
foreign material (even dust) in the plates.

OP: look for a fairly large unit that moves with the tuning knob. It
will be silver with a series of interwoven aluminum plates. They should
mesh together without touching...even a little. Can be cleaned out with
compressed air, or vacuum. Straightening is a little more finicky.

Careful: Fragile!

jak

 

[jakdedert]

jakdedert wrote:

hr(bob) hofmann@att.net wrote:
On Jan 7, 12:17 pm, "N_Cook" <dive...@tcp.co.uk> wrote:
Do the stations agree with the scale markings? ie someone restringed
wrongly.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list
onhttp://home.graffiti.net/diverse:graffiti.net/


What is the tuning mechanism, if it is a moving variable capacitor,
maybe the plates are shorting, that would explain the deadness at the
same points in the dial for both am and fm.

That would be my guess as well...shorting could mean bent plates or
foreign material (even dust) in the plates.

OP: look for a fairly large unit that moves with the tuning knob. It
will be silver with a series of interwoven aluminum plates. They should
mesh together without touching...even a little. Can be cleaned out with
compressed air, or vacuum. Straightening is a little more finicky.

Careful: Fragile!

jak

Picture of the part described above:
<http://www.classicsansui.net/images/Literature/Receivers/661/661b.jpg>
It's the silver thing at the extreme left of the circuit board in the
first picture.


Remove everything from "661" on, in the URL to get to the rest of the
brochure. That's a pretty nice piece to get for free....

jak

 

[Reinhard Zwirner]

"hr(bob) hofmann@att.net" schrieb:

On Jan 7, 12:17 pm, "N_Cook" <dive...@tcp.co.uk> wrote:
Do the stations agree with the scale markings? ie someone restringed
wrongly.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/

What is the tuning mechanism, if it is a moving variable capacitor,
maybe the plates are shorting, that would explain the deadness at the
same points in the dial for both am and fm.

OTOH: The plate packets for FM tuning aren't the same as for AM
tuning ...

And the distance between the FM plates is IMHO too big as there
could be a short.

Just my 2 cents

Reinhard

 

Hi Everyone: Thanks so much for your help so far!

I opened up the unit and looked at the capacitor wings on the fm
tuner. Didn't see anything touching or out of alignment.

Changes to my initial information:

1. The AM band is now working fine. Good signals. The frequency
indicator is out of alignment with the stations but that can be lived
with just fine because it is in alignment with the frequencies for the
FM band which I'm more concerned about.

2. I plugged in headphones and tuned along the entire length of the FM
band with the volume jacked all the way up. I CAN HEAR every station
along the band. And I confirmed they're the right frequencies when
compared with the digitially tuned walkman.

So it seems the problem is that most of the frequencies on the FM band
are not being amplified whereas about 3 stations do come in at full
amplification.

Any thoughts as to how I might proceed now would be appreciated.
Thanks again!

Gord

 

[Mark Zenier]

In article <0b0162a1-7a3a-432a-bd00-2d307f5de2fb@r15g2000prd.googlegroups.com>,
<imseakin@yahoo.com> wrote:

So it seems the problem is that most of the frequencies on the FM band
are not being amplified whereas about 3 stations do come in at full
amplification.

One possibility, the ones you can get are mono, or too weak for it
to switch to the stereo signals. And your stereo demodulator or
the preamp or audio switch is bad.

Mark Zenier mzenier@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)

 

After some further examination around with the receiver, I noticed a
button on the front called, "FM Muting OFF". I pressed it. All of the
stations were once again coming in strongly and clearly amplified.

Problem solved!

Thank you to everyone for your suggestions and help with diagnosing
this situation!

Best Wishes,


Gord

 

On Thu, 15 Jan 2009 06:45:23 -0800 (PST), imseakin@yahoo.com wrote:

After some further examination around with the receiver, I noticed a
button on the front called, "FM Muting OFF". I pressed it. All of the
stations were once again coming in strongly and clearly amplified.

Problem solved!

Thank you to everyone for your suggestions and help with diagnosing
this situation!

Best Wishes,


Gord
FM muting is essentially a squelch function designed to mute the hiss

between stations. It sounds like it is faulty or adjusted
incorrectly. However, once your desired station is tuned in, it
serves no purpose at all so you are perfectly OK leaving it off.

Pat

 

On Thu, 15 Jan 2009 06:45:23 -0800 (PST), imseakin@yahoo.com wrote:

After some further examination around with the receiver, I noticed a
button on the front called, "FM Muting OFF". I pressed it. All of the
stations were once again coming in strongly and clearly amplified.

Problem solved!

Thank you to everyone for your suggestions and help with diagnosing
this situation!

Best Wishes,


Gord

What Sansui do you have? On the Sansui TU-9500 the mute level can be
adjusted on the back of the tuner. The AM stick antenna mounted on the
back is tunable by sliding in and out.

 

[Kendra Weissbein]

On Jan 7, 9:38 am, imsea...@yahoo.com wrote:

I just found an old discarded Sansui receiver. It works well in all
respects except a large middle section of the AM and FM band don't
receive any stations. A couple of stations on the extreme ends of each
band come in loud and clear, distortion free.

All other aspects of the receiver work fine.

Is there a way that I can fix the tuner section by re-winding coils or
something else I can try that's reasonably inexpensive. I am not an
electronics expert but I am open to any ideas.

Thanks,

Gord

maybe you need to hook the son of a bitch to an outdoor antenna?

 

[jakdedert]

tnom@mucks.net wrote:

On Thu, 15 Jan 2009 06:45:23 -0800 (PST), imseakin@yahoo.com wrote:

After some further examination around with the receiver, I noticed a
button on the front called, "FM Muting OFF". I pressed it. All of the
stations were once again coming in strongly and clearly amplified.

Problem solved!

Thank you to everyone for your suggestions and help with diagnosing
this situation!

Best Wishes,


Gord

What Sansui do you have? On the Sansui TU-9500 the mute level can be
adjusted on the back of the tuner. The AM stick antenna mounted on the
back is tunable by sliding in and out.

Uh...do as I didn't; read the header.

Somehow, I got that this problem occurred on both AM & FM, hence advised
that it must be a problem with the tuning cap. Reading again, I
realized there was no mention of AM.

The problem (and model #) was succinctly stated in the subject header.

jak

 

[jakdedert]

jakdedert wrote:

tnom@mucks.net wrote:
On Thu, 15 Jan 2009 06:45:23 -0800 (PST), imseakin@yahoo.com wrote:

After some further examination around with the receiver, I noticed a
button on the front called, "FM Muting OFF". I pressed it. All of the
stations were once again coming in strongly and clearly amplified.

Problem solved!

Thank you to everyone for your suggestions and help with diagnosing
this situation!

Best Wishes,


Gord

What Sansui do you have? On the Sansui TU-9500 the mute level can be
adjusted on the back of the tuner. The AM stick antenna mounted on the
back is tunable by sliding in and out.

Uh...do as I didn't; read the header.

Somehow, I got that this problem occurred on both AM & FM, hence advised
that it must be a problem with the tuning cap. Reading again, I
realized there was no mention of AM.

The problem (and model #) was succinctly stated in the subject header.

jak

Somebody posted the entire OP in another reply, and it apparently 'did'
state that the problem occurred also on AM. (My news supplier purged
the OP.) I guess the takeaway lesson is to read both the header and the
body, then ask further questions if they don't agree.

So...did the problem also occur on AM? If so, how did pressing the FM
mute button solve that?

jak

 

On Jan 16, 12:26 pm, jakdedert <jakded...@bellsouth.net> wrote:

jakdedert wrote:
t...@mucks.net wrote:
On Thu, 15 Jan 2009 06:45:23 -0800 (PST), imsea...@yahoo.com wrote:

After some further examination around with the receiver, I noticed a
button on the front called, "FM Muting OFF". I pressed it. All of the
stations were once again coming in strongly and clearly amplified.

Problemsolved!

Thank you to everyone for your suggestions and help with diagnosing
this situation!

Best Wishes,

Gord

WhatSansuido you have? On theSansuiTU-9500 the mute level can be
adjusted on the back of the tuner. The AM stick antenna mounted on the
back is tunable by sliding in and out.

Uh...do as I didn't; read the header.

Somehow, I got that this problem occurred on both AM & FM, hence advised
that it must be a problem with the tuning cap.  Reading again, I
realized there was no mention of AM.

The problem (and model #) was succinctly stated in the subject header.

jak

Somebody posted the entire OP in another reply, and it apparently 'did'
state that the problem occurred also on AM.  (My news supplier purged
the OP.) I guess the takeaway lesson is to read both the header and the
body, then ask further questions if they don't agree.

So...did the problem also occur on AM?  If so, how did pressing the FM
mute button solve that?

jak- Hide quoted text -

- Show quoted text -

Hi Jak:

Initially thought the AM band was problematic as well. in a subsequent
post I indicated the AM was fine, just the FM was un-amplified.

Needless to say, everything's great. Thanks for your help.

Gord