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schematic/info on BC890XLT?



 
 
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  #1  
Old March 7th 05, 04:07 AM
John KB5AG
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Default schematic/info on BC890XLT?

I have a Uniden BC890XLT that seems to work normally, but receives nothing.
A Google search comes up with a similar problem to mine, but I don't see a
solution.
There's an IC, a Sharp IR3MO3A which is running super hot. It's switching
regulator IC, but I'm not sure what its purpose is, since most of the set
runs from the 5 and 8v linear regulators in the power supply.
Anyone had any experience with this? Is there a schematic anywhere
available for this?

Thanks,
John


  #2  
Old March 8th 05, 07:19 PM
Mac
Guest
 
Posts: n/a
Default


"John KB5AG" wrote in message
...
I have a Uniden BC890XLT that seems to work normally, but receives

nothing.
A Google search comes up with a similar problem to mine, but I don't see a
solution.
There's an IC, a Sharp IR3MO3A which is running super hot. It's switching
regulator IC, but I'm not sure what its purpose is, since most of the set
runs from the 5 and 8v linear regulators in the power supply.
Anyone had any experience with this? Is there a schematic anywhere
available for this?

Thanks,
John


John, the IR3MO3A is IC 12.

Program 162.400 and the voltages should measure;

Pin 1 - 12.85
Pin 2 - 0
Pin 3 - 0.54
Pin 4 - 0
Pin 5 - 1.27
Pin 6 - 12.85
Pin 7 - 12.85
Pin 8 - 12.85

There is a capacitor to ground off pins 1 and 6 that may have become leaky.
C63 and C65 are both located near the I.C.
Pin 6 provides the input voltage to I.C. 7, an L78MO5CV. If this regulator,
or some of its circuitry, is shorted or leaky this drain may be causing the
excess heat on IC 12.

Hope this helps you. Keep us posted!

Mac



  #3  
Old March 8th 05, 07:30 PM
Mac
Guest
 
Posts: n/a
Default


"Mac" wrote in message
...

"John KB5AG" wrote in message
...
I have a Uniden BC890XLT that seems to work normally, but receives

nothing.
A Google search comes up with a similar problem to mine, but I don't see

a
solution.
There's an IC, a Sharp IR3MO3A which is running super hot. It's

switching
regulator IC, but I'm not sure what its purpose is, since most of the

set
runs from the 5 and 8v linear regulators in the power supply.
Anyone had any experience with this? Is there a schematic anywhere
available for this?

Thanks,
John


John, the IR3MO3A is IC 12.

Program 162.400 and the voltages should measure;

Pin 1 - 12.85
Pin 2 - 0
Pin 3 - 0.54
Pin 4 - 0
Pin 5 - 1.27
Pin 6 - 12.85
Pin 7 - 12.85
Pin 8 - 12.85

There is a capacitor to ground off pins 1 and 6 that may have become

leaky.
C63 and C65 are both located near the I.C.
Pin 6 provides the input voltage to I.C. 7, an L78MO5CV. If this

regulator,
or some of its circuitry, is shorted or leaky this drain may be causing

the
excess heat on IC 12.

Hope this helps you. Keep us posted!

Mac



Correction -- actually the 12.85 volts on pin 6 of IC12 comes from the B+
source..(via the power switch on the volume control).....and that line also
feeds IC 7.
Still, I would look at the two caps right off IC12. Do you have audio and
squelch noise?

Mac


 




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