[Premium-Rx] WJ-8718 MFP PLL slow response

[Francesco Ledda]

If the VCO control voltage is stable, the VCO is very probably NOT the  
problem. I reccomend you to check the phase detector output. During  
unlock conditions, there should be a sawtooth. Follow the signal to  
the integrator to see what you get. Most likely, one of the PD is  
missing or the int/amp is busted.


On Jan 28, 2009, at 17:43, Gene Anderson <sidhu at ms12.hinet.net> wrote:

> A few months ago I posted a question about the problem I'm having with
> this receiver.  It takes time for the PLL for the first local  
> oscillator
> to lock.  It sounds as if someone were manually turning the tuning  
> dial
> as the frequency sweeps toward the desired frequency.  At some low
> frequencies, the receiver never fully locks onto the frequency.
>
> I increasingly suspect my 1st LO/VCO assembly (A5A1A1 - Type 791629).
> The voltages going into the unit (the three most significant bit  
> inputs
> and Tuning Voltage) all seem to be correct and stable.  Since this  
> is a
> sealed unit, I'm not sure if I should open it and attempt a component
> level repair.  I'm curious to know what you experts recommend.
>
>
> Best wishes for the Chinese New Year,
>
> Gene Anderson
> Taitung, Taiwan
>
> _______________________________________________
> Premium-Rx Mailing List
> To Post: premium-rx at mailman.qth.net
> For Info: http://mailman.qth.net/mailman/listinfo/premium-rx
> Visit the Website: http://www.premium-rx.org
> Email Help: paul at premium-rx.org
>