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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Help with Digital Alarm Clock Radio "repair"
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) |
#2
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"DMF" wrote in message ... 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 |
#3
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t.hoehler wrote:
"DMF" wrote in message ... 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. You might even get by with taking the antenna input to ground...a lot easier to locate. jak Regards and happy new years to all, Tom |
#4
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"jakdedert" wrote...
t.hoehler wrote: "DMF" wrote in message 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 some what 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. 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 |
#5
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DMF wrote:
"jakdedert" wrote... t.hoehler wrote: "DMF" wrote in message 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 some what 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. 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 Regards, David |
#6
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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 |
#7
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"DMF" writes:
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?" --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
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