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LED Tuning light
Brian Miller
I know this is the ultralight DX board, but it is the most active DX message board I know of so maybe someone can answer me even though this is not about ULR's.
My question is about a red LED tuning light on a portable Sony analog AM/FM radio - TFM-7250W. I got the thing at a garage sale last year for five bucks and I took it apart to clean it and to retro-fit it with an 18" outboard ferrite antenna. Everything is working great except for I cannot get the little red tuning led to light anymore. All of the connections look good to me but obviously I'm missing something. I guess my question is if anyone knows where that kind of a connection would be made generally. Thanks Brian Miller Berkley, MI USA |
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Kevin Schanilec
Hi Brian:
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Have you tried testing the LED itself? Not sure if these burn out. Disconnecting the trace to the LED (to test the LED) would allow you to test if there is voltage coming to the LED as well? Kevin S --- In ultralightdx@..., "Jerry" <brianalexmiller@...> wrote:
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Brian Miller
Hi Kevin -
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Thanks for the reply. I am so green on radio surgery that I'm not even quite sure what the "trace" is. The wires coming from the pcb to the led? What do I test with? I have the service manual for the radio. I had to get it to figure out how exactly to route the tuning dial string. I was amazed I was able to actually do it after a few tries. I've looked at the manual for awhile and can't figure the indicator light out from looking at the schematic, but again, I am far from a technician. I guess what might help me most is if you or someone could tell me the general concept behind what causes the indicator to light, where it usually would connect to..... anyway - Thanks again --- In ultralightdx@..., "dhsatyadhana" <dhsatyadhana@...> wrote:
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Kevin Schanilec
Hi Brian:
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Alas, all I can give is qualitative suggestions - I am probably about as handy with true tech work as you are, so wouldn't feel comfortable going any further. Anyone else??? Kevin --- In ultralightdx@..., "Jerry" <brianalexmiller@...> wrote:
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Hi Brian and Kevin,
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An LED that it not lighting (when it should) usually has two possible causes-- either the LED itself is burned out, or the active device (diode or transistor) driving the LED circuit has failed. Usually a technican would use a voltmeter to determine whether or not the LED input circuit has a positive voltage (to ground) when the LED should be lighting. If there is the normal positive voltage, the LED itself is probably bad. If the voltage on the input circuit is missing at all times, most likely the diode or transistor (or sometimes IC) driving the circuit has probably failed. You will need to locate these components on your schematic diagram, Brian, then check for that LED input voltage (either on the circuit board, or LED input pin). 73, Gary -----Original Message-----
From: dhsatyadhana <dhsatyadhana@...> To: ultralightdx <ultralightdx@...> Sent: Sun, Mar 27, 2011 5:48 pm Subject: [ultralightdx] Re: LED Tuning light Hi Brian: Alas, all I can give is qualitative suggestions - I am probably about as handy with true tech work as you are, so wouldn't feel comfortable going any further. Anyone else??? Kevin --- In ultralightdx@..., "Jerry" <brianalexmiller@...> wrote: the "trace" is. The wires coming from the pcb to the led? out how exactly to route the tuning dial string. I was amazed I was able to actually do it after a few tries. indicator light out from looking at the schematic, but again, I am far from a technician. the general concept behind what causes the indicator to light, where it usually would connect to..... > Thanks again <dhsatyadhana@> wrote: burn out. allow you to test if there is voltage coming to the LED as well? > > <brianalexmiller@> wrote:Kevin S most active DX message board I know of so maybe someone can answer me> I know this is the ultralight DX board, but it is the even though this is not about ULR's. portable Sony analog AM/FM radio - TFM-7250W. bucks and I took it apart to clean it and to retro-fit it with an 18">I got the thing at a garage sale last year for five outboard ferrite antenna. little red tuning led to light anymore. > >missing something.All of the connections look good to me but obviously I'm of a connection would be made generally. > USA |
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