Re: Display not working (and no Audio) FIXED !

   thanks for the tipoff...  i'm sure this will come in handy for someone.
At 21:22 8/21/2010, you wrote:
>
>
>I Have fixed the display problem on the 780 
>without requiring the Service Manual, but by using a schematic..
>
>The 9 Volt cct that powers the display's LCD 
>graphics (NOT the backlight, which runs on 12 
>vdc) WAS NOT working. If your LCD graphics are 
>out AND you do not get any signal audio (you may 
>still hear audio hiss or "screaching" 
>though)....the Zener diode that supplies the 
>reference for the 9 volt cct is likly burnt out. This
>Zener diode D27 is a UDZ10. It's a small surface 
>mounted chip, close to the Q2 transistor. This 
>diode is a 10 volt zener (not 9v, as it goes 
>through a resistor) UDZ10 zener. Any suitable sub should work.
>
>Hope this helps anyone with LCD display problems/ NO RF audio problems.
>
>Greg
>VA3VFO
>
>--- In 
><mailto:UnidenBC780XLT%40yahoogroups.com>[email protected], 
>"gregtheham" <radiotrade@...> wrote:
> >
> > Does anyone have a link or file for the 780 
> (or hand-held version) Serivce Manual? I Have 
> Schematics, which has been a big help. Service 
> may help tracing my problem though.
> >
> > BTW, I have lost LCD display (Backlight still OK) and RF signal Audio.
> > I am getting 12VDC where required to drive 
> 12v ccts, but suspect a 9v problem. The 2SD1667 
> tests OK (the one on the plug-in pigtail and 
> mounted to the chassis), but Q2 has 12VDC on 
> its output, which I believ should be 9V via the 
> zeiner D72...this controls Q4 for the 3V 
> ccts,and that seems OK..( I am getting 3v from 
> it) but that seems to confilict with my idea of 
> Q2 and/orD72 not working...I dont think I would get 3v
> >
> > I also want to trace what is referred to as 
> SW B, but cant find what that is...( IC 
> controled Softwware switch from main 
> processor?) cant find any origin for it, 
> althoughmany ccts show as continuing on to SW-B
> >
> > Can anyone help?
> >
> > Thanks
> > Greg
> >
>
>

Cheers Gig


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