| Author |
Message |
    
Harvester
| | Posted on Tuesday, January 07, 2003 - 9:24 pm: | 
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hello
got this old radio 138 no receive.i want this to run again. it's been modified .[extras]
is this something i can fix myself i.e. new finals ? it will talk . it used to work ,i bought it as is .complete w/3 single throw toggles.
do yall think i can just put new receive finals in it? im not educated in the electronics AT all but i can solder a mic . i'll need a tech and mailing instructions
thanks
harvester |
Rightwing
| | Posted on Wednesday, January 08, 2003 - 3:26 am: |
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check the pll to see if its shot .if it is get another pll also check the fet transistor just my 3 cents in |
2600
| | Posted on Wednesday, January 08, 2003 - 11:27 pm: |
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That radio is full of discontinued parts. Kinda makes it like working on a 40-year old car. Does the S-meter kick around on channel chatter? If it does, a simple problem like a bad speaker or mike can kill the receiver audio. If you can locate the audio chip on one side of the chassis, turn the radio over with the solder side up. Lick one finger, and lay it along the ten pins of the audio chip where they are soldered to the p.c. board. If the chip, speaker and mike are all functioning, you should get a rude squeal from the speaker. Your wet finger should create enough of a feedback circuit around the audio chip to get this noise. If it won't, you have one or more audio problems. The uPC1156 audio chip was discontinued years ago.
If the S-meter isn't kicking at all, try tapping the relay case. This part is also discontined, so if it's bad you'll either spend a lot to track one down, or to improvise a substitute. If it still transmits on the right channel, your PLL chip is NOT causing receiver problems. If it won't key, the PLL chip COULD cause trouble, especially if any of the "extra channel" switch wires has gotten loose and touched something "hot" with more than 5 volts on it. THAT might blow up the uPD858 PLL chip. Otherwise, it's a really reliable part that doesn't fail very often.
If this kind of simple troubleshooting doesn't get you anywhere, it's probably time for two things: 1) A schematic diagram, and 2) someone who can read it.
73 |
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