| Author |
Message |
    
Tombstone
| | Posted on Thursday, September 11, 2003 - 7:43 pm: | 
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Hi again guys,
I have a President JFK mobile, PC-713AG marked on the board. The radio had no receive. I plugged in an external speaker and all was fine, so I replaced the internal speaker with a known good one, still to no avail. I checked the external SP. jack to make sure it was making contact to run the internal SP. with no plug inserted, all OK. After jumping two traces that connect the external speaker jack to the board, the internal speaker came to life, all OK with good receive and transmit, loud audio. As I was replacing the covers, I heard what sounded like something loose rattling around inside. Upon inspection I discovered a 1/2 watt resistor loose floating around the insides!! The color bands look like brown-white gold, but they're not very clear so I'm not sure of the colors. The only place on the board I can find that looks like this resistor was soldered in is right underneath the 12 volt power connector, exactly the two traces that I had jumpered.(but not where I soldered in the jumper, I didn't accidentally unsolder the resistor) Ha-I removed the jumper and soldered in the resistor (R62 on the board) I got audio through the internal speaker now, but very low, so I left in the resistor and soldered the jumper across again. Now I got loud audio and all was well. I returned the radio to its owner and it worked well for a day and came back with no RX or TX, just panel lamps on. I removed the jumper and resistor, no change. I grounded the audio chip with my finger and got the loud hum/squeal. I have transmit voltage on the 1944 finals of 13.5 volts and the same on the driver. No RF output on the finals or the driver. Could the problem be in the TX-RX switching circuit? I don't know where to go from here. Thanks so much!
Tombstone |
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