Need help repairing a Uniden

Need help repairing a Uniden

Post by Geoffrey Hoffm » Sun, 10 Aug 1997 04:00:00

Hey, I am having trouble with a Uniden PRO 535e and i was wondering if
anyone would be able to help me with it.  It seems that I blew one of the
transistors, cause suddenly volume is very quiet, and the PA is pretty
quiet as well.  But, the behaviour is a little weird.

Anyway, is there a good source for info on fixing them, or should I just
send it back to Uniden?  (I would prefer no too, cause i have screwed with
it, and i don't want to bother explaining to them what i have done.)  If
it is a transistor, then i can easily do that.

Thanks for your time.

Geoffrey Hoffman

 
 
 

Need help repairing a Uniden

Post by Bill Eitne » Wed, 13 Aug 1997 04:00:00



> Hey, I am having trouble with a Uniden PRO 535e and i was wondering if
> anyone would be able to help me with it.  It seems that I blew one of the
> transistors, cause suddenly volume is very quiet, and the PA is pretty
> quiet as well.  But, the behaviour is a little weird.

        If the radio will transmit a carrier but no modulation
        the audio IC might be bad.

> Anyway, is there a good source for info on fixing them, or should I just
> send it back to Uniden?  (I would prefer no too, cause i have screwed with
> it, and i don't want to bother explaining to them what i have done.)  If
> it is a transistor, then i can easily do that.

> Thanks for your time.

> Geoffrey Hoffman


        Find the audio IC and check the signal at it's input and
        output pins.  The audio IC is a common failure point in
        many modern CBs.  You can find a pinout for it in the
        replacement catalogs (NTE, SK, etc.).  If the input signal
        is missing or distorted isolate that pin on the IC (wick
        up the solder and center the pin in it's hole) and check
        again.  If the signal is there and clean with the input
        pin isolated the chip is probably bad.  Two other verifi-
        cation tests are: 1. Look for low supply voltage at the
        chip's VCC pin.  2. Look for physical damage to the chip
        itself.  Often a chunk of the chip package will actually
        blow out.  If you find that the chip is bad make sure you
        test all the pins where there are capacitors to ground for
        shorts.  Oftentimes a capacitor will short taking the chip
        with it.    

        If these procedures aren't enough you can get service manuals
        from Uniden.  Here's a phone number: (317) 842-0280.

        Good luck.  
--

        -=[Bill Eitner]=-

 
 
 

Need help repairing a Uniden

Post by I408 » Thu, 14 Aug 1997 04:00:00



>    Find the audio IC and check the signal at it's input and
>    output pins.  The audio IC is a common failure point in
>    many modern CBs.  You can find a pinout for it in the
>    replacement catalogs (NTE, SK, etc.).  If the input signal
>    is missing or distorted isolate that pin on the IC (wick
>    up the solder and center the pin in it's hole) and check
>    again.  If the signal is there and clean with the input
>    pin isolated the chip is probably bad.  Two other verifi-
>    cation tests are: 1. Look for low supply voltage at the
>    chip's VCC pin.  2. Look for physical damage to the chip
>    itself.  Often a chunk of the chip package will actually
>    blow out.  If you find that the chip is bad make sure you
>    test all the pins where there are capacitors to ground for
>    shorts.  Oftentimes a capacitor will short taking the chip
>    with it.    

Good advice bill, one of mine looked like it took a rocket hit... :)
73
 
 
 

Need help repairing a Uniden

Post by SEAN FOLE » Thu, 14 Aug 1997 04:00:00

solid advice, bill.  we always refer to those "missing chunks" as "bullet
holes".  Sean