Help with Digital Alarm Clock Radio "repair"

[DMF]

All,

I was hoping someone here might be able to help me
with my clock radio. I have a GPX Digital Alarm/Clock
Radio (Model# D505) that I want to modify. I like to
set the morning alarm to play music but I don't want any
stations. I want it to wake me up with the soothing hiss
of white noise. I've tried setting it between stations, at the
ends of the dial, etc. but it still seems to pick up various
broadcasts and other chatter. So the questions is -- what
wire or component do I have to snip out of the circuit in
order to disable the radio's ability to pick up any signals?
I believe (and correct me if I am wrong) that if the antenna
portion of the (FM?) circuit is snipped out then I should
just get white noise, no matter where the tuner is set. Also,
would removing the antenna circuit create any kind of
problem for the downstream amplifying circuits?

Can this be done, if so, how? (This is a $9 radio, so I'm
not too concerned if I ruin it) Thank you.

Regards,
David (waiting with wire cutters at the ready)

 

[t.hoehler]

All,

I was hoping someone here might be able to help me
with my clock radio. I have a GPX Digital Alarm/Clock
Radio (Model# D505) that I want to modify. I like to
set the morning alarm to play music but I don't want any
stations. I want it to wake me up with the soothing hiss
of white noise. I've tried setting it between stations, at the
ends of the dial, etc. but it still seems to pick up various
broadcasts and other chatter. So the questions is -- what
wire or component do I have to snip out of the circuit in
order to disable the radio's ability to pick up any signals?
I believe (and correct me if I am wrong) that if the antenna
portion of the (FM?) circuit is snipped out then I should
just get white noise, no matter where the tuner is set. Also,
would removing the antenna circuit create any kind of
problem for the downstream amplifying circuits?

Can this be done, if so, how? (This is a $9 radio, so I'm
not too concerned if I ruin it) Thank you.

Regards,
David (waiting with wire cutters at the ready)

If you can figure out where the LO (local osc) is, you can just short its

output to ground. I did that to a discarded boom box board years ago, put it
in a small speaker enclosure, run the whole shebang off an old telephone
light wall wart, and use it to bathe the bedroom in pink noise, I rolled the
highs off somewhat with a cap. We've been using it for almost 16 years,
works great.
Regards and happy new years to all,
Tom

 

[jakdedert]

output to ground. I did that to a discarded boom box board years ago,
put it in a small speaker enclosure, run the whole shebang off an old
telephone light wall wart, and use it to bathe the bedroom in pink
noise, I rolled the highs off somewhat with a cap. We've been using
it for almost 16 years, works great.

You might even get by with taking the antenna input to ground...a lot easier
to locate.

jak

 

[DMF]

You might even get by with taking the antenna input to ground...a lot
easier to locate.

Thank you for the replies. I think finding that oscillator is a bit
beyond my skills. However, I can identify the tuner (clear plastic
box with metal plates that move when the tuner control is moved).
I can also see a ferrite bar AM antenna with a wire that connects
near the tuner. Would snipping this wire and grounding it get me
what I want? Also, I was hoping to use the FM band since the
hiss is more pleasant than AM hiss -- would grounding that wire
work to disable both bands or is there a separate FM antenna
lurking somewhere in the circuitry that I would have to ground?

Regards,
David

 

[jakdedert]

...

Thank you for the replies. I think finding that oscillator is a bit
beyond my skills. However, I can identify the tuner (clear plastic
box with metal plates that move when the tuner control is moved).
I can also see a ferrite bar AM antenna with a wire that connects
near the tuner. Would snipping this wire and grounding it get me
what I want? Also, I was hoping to use the FM band since the
hiss is more pleasant than AM hiss -- would grounding that wire
work to disable both bands or is there a separate FM antenna
lurking somewhere in the circuitry that I would have to ground?

Usually on cheap clock radios, there's a wire hanging out the back of the
unit which 'is' the FM antenna. There's got to be some sort. Occasionally,
I've seen a piece of metal which clamps on to the line cord to serve as an
FM antenna. Usually those units have external screw terminals for a
user-supplied antenna as well, though.

jak

 

[DMF]

All,

For those interested in the denouement of my plight... Thanks
to the advice on this forum, I was able to track down the FM
antenna wire. Putting it to ground (as suggested) caused the
radio to put out a bad rasping noise. Instead I clipped the wire
off as close to the PCB as I could -- thus limiting the amount of
signal getting to the tuner/amplifier. This did not completely solve
my problem because the radio would still pick spurious music,
warbles, etc when between stations or at the extreme ends of the
dial. So what I did was to tweak some adjustable POTs and
inductors near the tuner and I was able to shift the band off scale
so that when I tuned it as far right as it could go, no stations could
be picked up at all, just a pleasant hiss to nudge me awake in the
morning ;-)

Regards,
David

 

[Sam Goldwasser]

All,

For those interested in the denouement of my plight... Thanks
to the advice on this forum, I was able to track down the FM
antenna wire. Putting it to ground (as suggested) caused the
radio to put out a bad rasping noise. Instead I clipped the wire
off as close to the PCB as I could -- thus limiting the amount of
signal getting to the tuner/amplifier. This did not completely solve
my problem because the radio would still pick spurious music,
warbles, etc when between stations or at the extreme ends of the
dial. So what I did was to tweak some adjustable POTs and
inductors near the tuner and I was able to shift the band off scale
so that when I tuned it as far right as it could go, no stations could
be picked up at all, just a pleasant hiss to nudge me awake in the
morning ;-)

I pity the poor guy who might pick it from your trash when you finally
dump it. "What in the heck happened to this radaio?"

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