[R-390] 8640B

[Jon Schlegel]

Ben,

Of the two that I have, one tunes smooth and the other tunes somewhat 
stiff.  The one that tunes stiff works just fine as does yours.  I 
had to do some other repair work on this unit but I left the cavity 
alone.  I think HP claimed that the cavity oscillator inside these 
units was very much off limits even to their repair depots.  The 
cavity oscillator in these units is what really makes these things 
tick so if it's working for you, leave it.

Regards,
Jon
WA3MVM

At 02:53 PM 1/10/2011 -0600, Ben Loper wrote:
>This may be a tough question to answer, but how tight should the tuning knob
>on an 8640B be.  I know it shouldn't spin like a well adjusted R-390.  On
>mine it's consistent across the range and makes no weird noises, but there
>is definite resistance when I turn it and since this is the only one I've
>ever had I don't know if that's normal.  I assume the know should be fairly
>stiff to avoid it moving after you set it, but I'm just curios.  Mine works
>great.  Ben KJ4CC
>
>-----Original Message-----
>From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
>On Behalf Of Doug Massey
>Sent: Monday, January 10, 2011 2:35 PM
>To: Mack Rogers; r-390 at mailman.qth.net
>Subject: Re: [R-390] 8640B
>
>
>Amen to both posts!!!!!!!! They are the best....period.
>
>Doug Massey
>N4ZZT
>Massey Radio Labs
>Johnston SC 29832
>WWW.masseyradiolabs.com
>
>Mack Rogers <n4vgb at yahoo.com> wrote:
>
> >And here I thought myself as being a bit obsessive compulsive when I
> >purchased my second 8640. Bottom line is it's the biggest bang for the
> >buck out there at this time. It's a very good and accurate sig gen with
> >a super clean output.
> >
> >N4VGB
> >Mack Rogers
> >
> >
> >
> >
> >--- On Mon, 1/10/11, wa4aos at aol.com <wa4aos at aol.com> wrote:
> >
> >> From: wa4aos at aol.com <wa4aos at aol.com>
> >> Subject: [R-390] 8640B
> >> To: r-390 at mailman.qth.net, gcbojr at aol.com
> >> Date: Monday, January 10, 2011, 2:45 PM
> >>
> >>
> >>
> >>  Hi Group,
> >>
> >> I have 4) 8640B's in my electronics lab and use them often. I have
> >> them set up on various benches and that makes service, burn-in and
> >> evaluation all possible with minimal moving units around. I bought
> >> two of the from George Bojr in Texas and he has repaired another one
> >> for me. He has parts for the 8640B and does a GREAT job with service.
> >> The turn around was quick and I was very pleased. You can find them
> >> cheaper on ebay but understand you may get a dud and or one
> >> with split gears and other issues. George can not give you a
> >> NIST sticker but his equipment is calibrated and all of my
> >> units are dead on between units. He does sell on ebay but
> >> may have inventory for sale at any given time.
> >>
> >> Personally, I like the 8640B for receiver work. They are accurate,
> >> dependable and small compared to older units like the 606A/B..You can
> >> also use it's internal counter for external measurements, so, it's
> >> really two pieces of equipment, though, I have other counters,
> >>
> >> Typically, I let them warm up half an hour before I do any serious
> >> alignments as I would no matter what generator I use.. Like most HP
> >> gear, the 8640B accepts and external 10MHz reference input should you
> >> care to do that. I bought one of the 10MHz GPS receivers on ebay with
> >> antenna for around $150 and build an adequate distribution unit to
> >> reference a number of HP items in my lab. You can also find
> >> pulled Rubidium clocks with a 10MHz out very cheap now as
> >> well, under $100. Nothing like knowing you are dead on
> >> accurate.
> >> Keep in mind, the 10 MHz external reference is just
> >> something I wanted to have; I have a very bad case of
> >> gadget-itus. Hi Hi .
> >>
> >> The 8640B's calibrated are plenty good enough for almost anything you
> >> will need for working on HF receivers.
> >>
> >> His email address is
> >> www.gcbojr at aol.com
> >>
> >> 73,
> >> Glenn Scott WA4AOS
> >> DSM Labs
> >>
> >>
> >>
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> >
> >
> >
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