[Premium-Rx] HP8640B

[Carcia, Frank A. HS]

	hi Jan,
I'm right at the cavity with the counter, power meter and spectrum analyzer.
Now to find why the counter is also dead. I have a filter problem with one
generator in the shack on the 2 to 4 MHz. range. This new unit looks great
on all bands so one problem will be solved for sure. Also this new unit has
no cracked gears.   fc

-----Original Message-----
From: jan at skirrow.org [mailto:jan at skirrow.org]
Sent: Friday, March 14, 2003 11:33 AM
To: Carcia, Frank A. HS
Subject: Re: [Premium-Rx] HP8640B


Hi Frank ...

I've worked on this unit quite a bit. I wouldn't encourage you to do 
anything with the cavity itslef until you are sure it's nothing else. 
Problems I've had with output dropoff have always been something else.

Sources of trouble are the complex switched filters - does the counter 
behave the same way on all range settings, and at both top and bottom of 
each range (filters are switched for each range and about halfway within 
each range)? The output level uses a nice feedback system (the cavity 
operates at a constant output regardless of level setting). It could even 
be a problem in the meter amp itself.

You will need a manual - this thing is not a "kick it and see what happens" 
kind of gadget. Also, the major problem with these is often in the power 
supply. Flakey connections, etc. I had one were one PS board had an 
intermittent fuse!

Well worth the effort to fix up!

Jan


At 06:18 AM 3/14/03, you wrote:


> >       hi All,
> >       I just bought a broken HP8640B off Ebay.
> >       There appears to be a problem with the Cavity.
> >       The output drops very low after it has been
> >       on for a while. I have the procedure for setting
> >       the two levels. I wonder if anyone has ever
> >       taken one apart or ever seen this problem.
> >       The power supply voltages appear normal.
> >       I wonder if there is a feedback probe   adjustment and the
> > transistor type used
> >       in the oscillator. This was to be a hanger      queen but looks
> > clean with no cracked gears.
> >       It is the early model with wafer switches.
> >                               TNX,
> >                               fc
>
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