Sherwood tuner died.

[T i m]

Hi All,

I have a fairly old but lightly used Sherwood R 125 RDS ss FM receiver
but note the FM tuner has died.

Well, it's working in as much it appears to auto tune and lock onto a
station and with the volume turned up you can hear it trying to work
but it's if it's heavily muted (and distorted). FWIW the AM side seems
'alive' but I have no aerial on there atm to really test it.

I *think* I had something similar years ago on an old Memorex FM tuner
and I think that was the cct that muted the signal between stations
muting all the time?

Anyone seen this before and any ideas re a fix please (as it's quite a
nice unit otherwise).

Cheers, T i m

 

[William Sommerwerck]

Wasn't he a famous playwright?

 

[T i m]

On Tue, 13 Oct 2009 08:20:28 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

Wasn't he a famous playwright?

You aren't getting confused with Robin Hoods 'hood' are you?

T i m

 

[Bennett Price]

Are you sure it's the tuner and not the amp to which it's connected?


T i m wrote:

Hi All,

I have a fairly old but lightly used Sherwood R 125 RDS ss FM receiver
but note the FM tuner has died.

Well, it's working in as much it appears to auto tune and lock onto a
station and with the volume turned up you can hear it trying to work
but it's if it's heavily muted (and distorted). FWIW the AM side seems
'alive' but I have no aerial on there atm to really test it.

I *think* I had something similar years ago on an old Memorex FM tuner
and I think that was the cct that muted the signal between stations
muting all the time?

Anyone seen this before and any ideas re a fix please (as it's quite a
nice unit otherwise).

Cheers, T i m

 

[PeterD]

On Tue, 13 Oct 2009 15:56:34 +0100, T i m <news@spaced.me.uk> wrote:

Hi All,

I have a fairly old but lightly used Sherwood R 125 RDS ss FM receiver
but note the FM tuner has died.

Well, it's working in as much it appears to auto tune and lock onto a
station and with the volume turned up you can hear it trying to work
but it's if it's heavily muted (and distorted). FWIW the AM side seems
'alive' but I have no aerial on there atm to really test it.

I *think* I had something similar years ago on an old Memorex FM tuner
and I think that was the cct that muted the signal between stations
muting all the time?

Anyone seen this before and any ideas re a fix please (as it's quite a
nice unit otherwise).

Cheers, T i m

Take it you don't have a schematic so that would be your first step.
Then trace with a signal tracer and see if you can find your missing
audio?

 

[T i m]

On Tue, 13 Oct 2009 09:24:18 -0700, Bennett Price
<bjprice@cal.berkeley.edu> wrote:

Are you sure it's the tuner and not the amp to which it's connected?

Yes because it's a receiver (tuner amp) and all the other inputs seem

to be ok (I was listening to some streaming audio via my PC earlier
via the AUX input).

The thing is, I thought it was the aerial as it feeds two radios we
have here and neither work. However, putting a bit of wire in the back
of this Sherwood gave exactly the same effect (we have a strong FM
signal round here).

Cheers, T i m

 

[T i m]

On Tue, 13 Oct 2009 09:50:06 -0700 (PDT), "William R. Walsh"
<wm_walsh@hotmail.com> wrote:

Hi!

Anyone seen this before and any ideas re a fix please (as it's quite
a nice unit otherwise).

Well, I think that the first thing I'd do is check the controls on the
amplifier. Make sure that nobody's turned on a "tape monitor" switch
or something along those lines.

Checked.

And if that fails, have you tried the tuner with another amplifier?

Sorry, it's a tuner - amp (The AUX was working earlier and I'm using
the CD in right now).

If you want to test the AM side of things, your finger or a short
piece of wire will do in a pinch for an antenna.

Ok, I'll give that a go, thanks.

Cheers, T i m

 

[T i m]

On Tue, 13 Oct 2009 12:28:50 -0400, PeterD <peter2@hipson.net> wrote:

Anyone seen this before and any ideas re a fix please (as it's quite a
nice unit otherwise).


Take it you don't have a schematic so that would be your first step.

No and it would yes. ;-(

Then trace with a signal tracer and see if you can find your missing
audio?

Yup ... or hope it's a common fault and someone tells me to cut D54
out and put up with the inter-tuning noise. ;-)

Cheers, T i m

 

[T i m]

On Tue, 13 Oct 2009 12:28:50 -0400, PeterD <peter2@hipson.net> wrote:

Take it you don't have a schematic so that would be your first step.

I think this is the service manual for what could be the same model
inside (the controls seem to be in different places but the same range
of controls).

http://preview.tinyurl.com/yfepxgy

Could it be Q8R/L, top right on their P8? They seem to specifically
mute the output of the tuner but if both channels are quiet, what are
the chances of both devices being faulty? Does this then leave the
tuner itself or maybe the control inputs(s) to the tuner mutes?

I guess the mute it refers to here is how it kills all the unwanted
outputs being mixed together (rather than the master 'mute' on the
main amp as such)?

I've not read all the manual yet so maybe the answer is there so I'll
carry on RTFM. ;-)

Cheers, T i m

 

[William R. Walsh]

Hi!

Anyone seen this before and any ideas re a fix please (as it's quite
a nice unit otherwise).

Well, I think that the first thing I'd do is check the controls on the
amplifier. Make sure that nobody's turned on a "tape monitor" switch
or something along those lines.

And if that fails, have you tried the tuner with another amplifier?
Changed the cables going from tuner to amplifier? (I mention this
because I had a set of RCA audio cables recently that didn't work but
did not test open anywhere. For whatever reason, the shield connection
was very high resistance.)

If you want to test the AM side of things, your finger or a short
piece of wire will do in a pinch for an antenna.

William

 

[Jamie]

T i m wrote:

On Tue, 13 Oct 2009 09:24:18 -0700, Bennett Price
bjprice@cal.berkeley.edu> wrote:


Are you sure it's the tuner and not the amp to which it's connected?


Yes because it's a receiver (tuner amp) and all the other inputs seem
to be ok (I was listening to some streaming audio via my PC earlier
via the AUX input).

The thing is, I thought it was the aerial as it feeds two radios we
have here and neither work. However, putting a bit of wire in the back
of this Sherwood gave exactly the same effect (we have a strong FM
signal round here).

Cheers, T i m
If memory serves, didn't those units have AUX IN and OUT in the back

where you had to place jumper cables in ? other wise, you didn't get
any sound.. Maybe a little leakage but that was it..
ALso, maybe you're using an EQ that isn't working?

 

[T i m]

On Tue, 13 Oct 2009 20:22:47 -0400, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

If memory serves, didn't those units have AUX IN and OUT in the back
where you had to place jumper cables in ?
other wise, you didn't get
any sound.. Maybe a little leakage but that was it..

Erm, I think it has a tape loop but that's about it? I'm pretty sure
it *was* working ok and now it isn't and I've not touched it round the
back for *years*.

ALso, maybe you're using an EQ that isn't working?

Nope, this is an all_in_one receiver. I've since found the owners
handbook on the net:

http://www.etronics.co.kr/english/download/pdf/R-125%28a%29.pdf

I read the service manual through yesterday and I think I have a
slightly better understanding of how the mute thing works for each of
the in / output and now don't think that's the problem. I turned the
volume right up when it was on FM and could tune it in to many
stations [1] (that you could just hear in the background). Then when
you selected say the 'Phono' input the set went quiet (suggesting the
FM was being 'muted' when de-selected and therefore (probably)
un-muted when selected).

The faultfinding suggests a transistor or a couple of ICs just after
front end could be at fault so I might go in there for a look
sometime.

Alternatively I could look for a compact DAB tuner and plug that into
the AUX as that seems to be the way we are going these days (even here
in the UK).

Cheers, T i m

 

[T i m]

On Wed, 14 Oct 2009 10:00:00 +0100, T i m <news@spaced.me.uk> wrote:

Ooops, bad form (again) I know ..

I turned the
volume right up when it was on FM and could tune it in to many
stations [1]

[1] I note the stereo indicator never comes on, even when it sounds
like it's tuned into a local station that I know is stereo. Would that
confirm my thoughts that it's a component after the front end, before
the stereo decoding happens?

Cheers, T i m

 

[Mark Zacharias]

"T i m" <news@spaced.me.uk> wrote in message
news:g549d554om3aarogeokm7meeanfa46lhsj@4ax.com...

Hi All,

I have a fairly old but lightly used Sherwood R 125 RDS ss FM receiver
but note the FM tuner has died.

Well, it's working in as much it appears to auto tune and lock onto a
station and with the volume turned up you can hear it trying to work
but it's if it's heavily muted (and distorted). FWIW the AM side seems
'alive' but I have no aerial on there atm to really test it.

I *think* I had something similar years ago on an old Memorex FM tuner
and I think that was the cct that muted the signal between stations
muting all the time?

Anyone seen this before and any ideas re a fix please (as it's quite a
nice unit otherwise).

Cheers, T i m

Digital tuners often exhibit a problem where the discriminator alignment
drifts enough that problems similar to yours occur.

Really needs to go to a shop. It's a simple alignment, but not for a DIY
with no service manual or training.

Mark Z.

 

[William Sommerwerck]

I note the stereo indicator never comes on, even when it sounds
like it's tuned into a local station that I know is stereo. Would that
confirm my thoughts that it's a component after the front end, before
the stereo decoding happens?

The indicator light might be burned out. Or, as someone else is pointed out,
the tuner might be slightly out of alignment.

 

[T i m]

On Wed, 14 Oct 2009 05:46:17 -0500, "Mark Zacharias"
<mark_zacharias@sbclobal.net> wrote:

Digital tuners often exhibit a problem where the discriminator alignment
drifts enough that problems similar to yours occur.

Ah, ok.

Really needs to go to a shop. It's a simple alignment, but not for a DIY
with no service manual or training.

I think I now have the service manual so potentially some test /
alignment procedures to follow. I have a scope, DMMs and frequency
counter etc but no signal injection kit but could probably rig
something if need be.

I would be happy to take such a thing to 'a shop' 1) I don't think we
have many over here (UK) any more and 2) if we did I think the work
would probably out-value the equipment?

I have been an electronics service engineer for much of my life it was
mainly on data-transmission / communications kit. I even got my Radio
Amateur ticked to do Packet radio. ;-)

I've had a look about and a DAB / FM tuner can be had for about Ł60
new so I could use that instead of the tuner part (I'm not too
bothered about 'quality' as long as it sounds ok and works).

Cheers, T i m (G7ICW)

p.s. I might see if I can find a local 'radio enthusiast' who might be
interested in having a look for a beer.

 

[PeterD]

On Tue, 13 Oct 2009 19:35:28 +0100, T i m <news@spaced.me.uk> wrote:

On Tue, 13 Oct 2009 12:28:50 -0400, PeterD <peter2@hipson.net> wrote:


Take it you don't have a schematic so that would be your first step.

I think this is the service manual for what could be the same model
inside (the controls seem to be in different places but the same range
of controls).

http://preview.tinyurl.com/yfepxgy

Could it be Q8R/L, top right on their P8? They seem to specifically
mute the output of the tuner but if both channels are quiet, what are
the chances of both devices being faulty? Does this then leave the
tuner itself or maybe the control inputs(s) to the tuner mutes?

Could be, and certaily a good starting point. Maybe open the collector
and see if you have audio (there). Also check the input to the low
pass filter that feeds the audio. If there is no audio on the optput
of IC3, you may be SOL...

 

[T i m]

On Wed, 14 Oct 2009 03:53:43 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

I note the stereo indicator never comes on, even when it sounds
like it's tuned into a local station that I know is stereo. Would that
confirm my thoughts that it's a component after the front end, before
the stereo decoding happens?

The indicator light might be burned out.

It's part of the fluorescent display so difficult to tell.

Or, as someone else is pointed out,
the tuner might be slightly out of alignment.

Whilst I'm sure that's not impossible I'm not sure how likely? I say
that because I've had many radios / tuners / scanners over the years
and I'm not aware of that happening, especially without some external
influence. However, I guess components can age, capacitors dry-up etc
....

I will have a quick look in there and see if the schematics I have
look correct for my unit and then see if I can follow anything through
and some of the alignment procedures that I can with my limited (for
this sort of work) service equipment. I guess even a tweak of a
pre-marked coil or pot should tell me if I'm in the right area or not
(no difference = wrong area or it's *way* off / broken)). ;-)

As I have mentioned elsewhere, a safer, quicker and potentially better
solution (as no one has come up with a specific weakness / experience
with this particular unit so far) is an external FM / DAB tuner as
then I can enjoy the DAB stuff as well.

Cheers, T i m

 

[Mark Zacharias]

"T i m" <news@spaced.me.uk> wrote in message
news:53obd554hbsbesei3vup43ht3lohgotst1@4ax.com...

On Wed, 14 Oct 2009 03:53:43 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

[1] I note the stereo indicator never comes on, even when it sounds
like it's tuned into a local station that I know is stereo. Would that
confirm my thoughts that it's a component after the front end, before
the stereo decoding happens?

The indicator light might be burned out.

It's part of the fluorescent display so difficult to tell.

Or, as someone else is pointed out,
the tuner might be slightly out of alignment.

Whilst I'm sure that's not impossible I'm not sure how likely? I say
that because I've had many radios / tuners / scanners over the years
and I'm not aware of that happening, especially without some external
influence. However, I guess components can age, capacitors dry-up etc
...

Extremely common.

Mark Z.

 

[Mark Zacharias]

"T i m" <news@spaced.me.uk> wrote in message
news:9hebd5p7jaivik88bjkshnd6jshimher8m@4ax.com...

On Wed, 14 Oct 2009 05:46:17 -0500, "Mark Zacharias"
mark_zacharias@sbclobal.net> wrote:


Digital tuners often exhibit a problem where the discriminator alignment
drifts enough that problems similar to yours occur.

Ah, ok.

Really needs to go to a shop. It's a simple alignment, but not for a DIY
with no service manual or training.

I think I now have the service manual so potentially some test /
alignment procedures to follow. I have a scope, DMMs and frequency
counter etc but no signal injection kit but could probably rig
something if need be.

I would be happy to take such a thing to 'a shop' 1) I don't think we
have many over here (UK) any more and 2) if we did I think the work
would probably out-value the equipment?

I have been an electronics service engineer for much of my life it was
mainly on data-transmission / communications kit. I even got my Radio
Amateur ticked to do Packet radio. ;-)

I've had a look about and a DAB / FM tuner can be had for about Ł60
new so I could use that instead of the tuner part (I'm not too
bothered about 'quality' as long as it sounds ok and works).

Cheers, T i m (G7ICW)

p.s. I might see if I can find a local 'radio enthusiast' who might be
interested in having a look for a beer.

Typically there are two test points physically near the discriminator
transformer. One uses a DVM to measure the DC millivolts across these two
points, while tuned to a station near 98 mHz. Adjust for zero millivolts. A
center bar-graph display, such as seen on Fluke meters, is useful - one can
adjust the moving voltage to center around zero.

Mark A.