[Test-Equipment] HP 8640B questions

[Pete Lancashire]

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
> > ______________________________________________________________
> > Test-Equipment mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/test-equipment
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Test-Equipment at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> ______________________________________________________________
> Test-Equipment mailing list
> Home: http://mailman.qth.net/mailman/listinfo/test-equipment
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Test-Equipment at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>