[Test-Equipment] HP 8640B questions

[Barry]

Some older models (like mine) use rotary switch with old-style contacts so they don't suffer from that problem.

Thanks,
Barry - N4BUQ

----- Original Message -----
> From: "Pete Lancashire" <pete at petelancashire.com>
> To: "Discussion of Electronic Test Equipment" <test-equipment at mailman.qth.net>
> Cc: bonddaleena at aol.com
> Sent: Thursday, April 21, 2016 11:50:13 AM
> Subject: Re: [Test-Equipment] HP 8640B questions
> 
> one note I want to make sure everybody that owns an 8640.
> 
> before you take any of the covers off  make sure your generator is sitting
> on something that can catch anything that will fall out. for example  a
> sheet of butcher paper. the failures that are starting to show up now days
> are the  rotary  switch contacts breaking off. they are extremely small and
> delicate. they are heat staked to a clear plastic disc. if they get damaged
> they are almost impossible to repair. the fixes the disk has unused posts
> 180 degrees over. I use an electronic grade RTV  since the force is
> extremely small and it allows me to repair  if things go wrong
> On Apr 21, 2016 9:37 AM, "Barry" <n4buq at knology.net> wrote:
> 
> > Hi Ron,
> >
> > FWIW, I don't think the signal goes through the counter on its way to the
> > output.  In fact, I don't think the counter is actually sampling the output
> > but only the basic range of frequencies and the appropriate multiplier
> > controls the value seen on the display.
> >
> > Sound like you might have a damaged attenuator?  There was on on eBay
> > recently for a reasonable price but I don't see it anymore.  There are a
> > couple out there, but they're a bit expensive (for me) and, of course, it's
> > hard to guarantee they're good.
> >
> > I'd check the signal going into the attenuator and if that's good, then
> > you might have a bad attenuator.  If there's no signal there, then you'll
> > have to look elsewhere.
> >
> > That's sort of generic, but maybe it will get you towards a fix for it.
> >
> > The HP group would be another great place for advice.
> >
> > Thanks,
> > Barry - N4BUQ
> >
> > ----- Original Message -----
> > > From: "Ron Bussiere via Test-Equipment" <test-equipment at mailman.qth.net>
> > > To: test-equipment at mailman.qth.net
> > > Cc: bonddaleena at aol.com
> > > Sent: Thursday, April 21, 2016 11:19:59 AM
> > > Subject: [Test-Equipment] HP 8640B questions
> > >
> > >
> > > Hi. I have a pretty nice 8640B. Don't use it much, but last year while
> > using
> > > it, I broke the FM slide switch. I thought it was an easy fix. NOT!
> > > After removing the 'counter module', and not being able to even see the
> > > broken switch, I reinstalled the counter.
> > > This was very difficult with my large hands! Must have been designed by
> > > Lucifer himself.
> > >
> > > Now, I have another problem. I have NO output from the front N connecter
> > on
> > > ANY setting of the attenuator. Nothing.
> > > The counter works and I have a big, fat signal out on the rear BNC RF out
> > > connector. It is of course not adjustable in amplitude.
> > > The output on the rear indicates the correct frequency (with an external
> > > counter) the same as the 8640B's counter.
> > > I do have some nice attenuators that are good to over 1 gHZ, but would
> > rather
> > > the generator function correctly.
> > > I don't care about the FM mode, probably never use it anyway.
> > >
> > > I was wondering if one of the miniature connectors on the bottom of the
> > > counter unit could have been damaged? 2 are the 'rigid' type and I tried
> > > many, many times to reinsert the counter assy, but had problems with the
> > > flexible coax connector preventing the unit from sitting flush.
> > Wondering if
> > > the signal path went through the counter to the attenuator. Yes, I have a
> > > manual, but it's in a spot I can't get to right now, darn!
> > >
> > > I have a very nice chap up in Mass. helping me on line, but thought I'd
> > ask
> > > here as well.
> > >
> > > Sorry to be so wordy, but...............
> > >
> > > ron
> > > N4UE
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