Question about Radio Communications
I have checked/replaced the inline fuse, used a multimeter to check the reverse power diode (I get an ''open'' reading between red and black terminals on the radio) , still no power, no lights, nothing. For about a month, the meter light on the radio would dim when you key the mic, then finally it would not turn on at all.
SOURCE: VHF transmit power
Hi, It is not typical but neither is there a problem with the radio. Transmit Power output is loosely dependent on the: 1. Frequency or channel you are transmitting. Normally, Marine Band VHF are calibrated for max (25 in your radio) at Ch16 or 156.800Mhz; 2. If the SWR of the antenna is not a flat 1.0, power tends to go down; 3. After some time, the TX side of the radio needs to be re-calibrated; 4. Power Supply - some radios will push max output only when powered with 13.8 and tends to go down when used with 12 volts. Hope this be of some help/idea. Post back should you need additional information. Good luck and kind regards.
Posted on Oct 04, 2007
Check around the pcboard where the dc goes to the board, sometimes the foil will burn. Also chec the transformer, Chec that one of the wires did not come off the plug in the back. When you replaced the protection diode did it blow again? If not keep checking for opens on the pc board. When you said it was dead do you mean no lights at all or no tx and rx?
Posted on Jan 26, 2009
Not knowing what kind of equipment you have, its hard to say, but .10 watt? Sounds like the buffer or driver also got involved. Usually you get 1/4-1/2 watt to the driver on a stock radio. I would also check the bias resistors like you suggested. Also check for burnt foil around the final you replaced. Good just be a slightly damaged circuit. Let me know if this helps.
Posted on Feb 04, 2009
Sounds like a "short" if it affects modulation + power. Try to inspect board with magnifier for solder bridges, and bad resistors. Change a few resistors near back with new ones. take out slugs near back finals like L10 or L20's not sure if its same as Uniden Pc68xl. but try that. I found turning L19 up to top gave great Modulation. clip D9, Sread coils 1/16 inch in back. Try to get lower carrier. Carrier does not mean anything much. Modulation is what you need. With less Carrier it may cool down that chip. It may be too wound out.
Posted on Mar 31, 2011
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When the power was reversed this shorted out one of the components, possibly an Operational Amplifier. This tells me that there is no diode protection and possibly the circuitry is exposed directly to the input power supply. The fix would be to find the shorted component with the use of a schematic and a multimeter. Once you correct the shorted component then if possible you can add diode protection by putting a diode (forward biased direction) in the path of the positive line.
Again you will need a schematic, and a multimeter to work on this problem.
I hope this helps,
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