HP 8640B - Need Help!

A

Andrea

Guest
Gentlemen,

A few days ago I became a (almost 100%) happy owner of a HP 8640B with
Options 001, 002 and 003. Unfortunately, this fine piece of equipment
suffered a subtle freight damage and demonstrated ZERO RF output when
checked. After some hours of work, I traced the fault to a Hybrid HP
Amplifier in the AM modulator, of which I've a photo:

http://andrea.modelberg.it/images/08640-67003.jpg

By shorting input and output of this IC I've been able to see a signal
at the output, although with reduced power and some distortion,
courtesy of the impedance mismatch. Unfortunately, all my attempts in
trying to find a replacement have been unsuccessful so far. Can anyone
point me in the right direction? All other functions seem to work just
fine, and the generator itself is in good shape and really worth the
effort to bring it back to life.

SeeYa!

/\
/--\ndrea

http://www.modelberg.com
ICQ #15014472
remove NOSPAM to e-mail me
 
Andrea wrote:

Gentlemen,

A few days ago I became a (almost 100%) happy owner of a HP 8640B with
Options 001, 002 and 003. Unfortunately, this fine piece of equipment
suffered a subtle freight damage and demonstrated ZERO RF output when
checked. After some hours of work, I traced the fault to a Hybrid HP
Amplifier in the AM modulator, of which I've a photo:

http://andrea.modelberg.it/images/08640-67003.jpg

By shorting input and output of this IC I've been able to see a signal
at the output, although with reduced power and some distortion,
courtesy of the impedance mismatch. Unfortunately, all my attempts in
trying to find a replacement have been unsuccessful so far. Can anyone
point me in the right direction? All other functions seem to work just
fine, and the generator itself is in good shape and really worth the
effort to bring it back to life.

SeeYa!

/\
/--\ndrea

http://www.modelberg.com
ICQ #15014472
remove NOSPAM to e-mail me
Click to expand...
I assume you checked with HP,and that they want a fortune for it....
If you have a good idea as to exactly what each pin is for, as well as
the function, input and output specs, maybe you can make a small
breadboard replacement?
 
On Sun, 24 Aug 2003 07:39:05 GMT, Robert Baer
<robertbaer@earthlink.net> wrote:

I assume you checked with HP,and that they want a fortune for it....
Click to expand...
Not exactly. I went through some refurbished test equipment dealers
that I know of. Never thought of HP in the first istance because of
their "10-years support and then you are on your own" policy. But it
might be worth a try, in fact. Actually, I'm not making a big problem
out of spending a fortune of it, as it's an expense which is going
into the insurance claim anyway.

If you have a good idea as to exactly what each pin is for, as well as
the function, input and output specs, maybe you can make a small
breadboard replacement?
Click to expand...
Nope. Not for a ultra-linear amplifier from 450 KHz to 550 MHz. I
doubt I could ever reproduce the gain, linearity and noise figure
that HP was able to put in. Unless I want to part with the excellent
performances of this generator, which is something I don't even
consider.

SeeYa!

/\
/--\ndrea

http://www.modelberg.com
ICQ #15014472
remove NOSPAM to e-mail me
 
On Sun, 24 Aug 2003 10:59:04 +0100, Robert Morein wrote:

Noise figure shouldn't be a problem for a generator.
Click to expand...
The 8640B is one of the lowest noise signal generators ever made. I
rather suspect that's what Robert had in mind when he got it.

If you're going to use it for testing links, it matters.

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
 
On Sun, 24 Aug 2003 18:51:25 +0100, Andrea wrote:

Fred,

'nuff said! I could have said that word by word. Except for my name,
that is :
Click to expand...
Sorry 'bout that. I just looked back up the headers for the name, and the
OP had scrolled up out of sight.

Must get new glasses.

I promise it won't happen again, honest :)

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
 
Andrea wrote:
On Sun, 24 Aug 2003 07:39:05 GMT, Robert Baer
robertbaer@earthlink.net> wrote:

I assume you checked with HP,and that they want a fortune for it....

Not exactly. I went through some refurbished test equipment dealers
that I know of. Never thought of HP in the first istance because of
their "10-years support and then you are on your own" policy. But it
might be worth a try, in fact. Actually, I'm not making a big problem
out of spending a fortune of it, as it's an expense which is going
into the insurance claim anyway.

If you have a good idea as to exactly what each pin is for, as well as
the function, input and output specs, maybe you can make a small
breadboard replacement?

Nope. Not for a ultra-linear amplifier from 450 KHz to 550 MHz. I
doubt I could ever reproduce the gain, linearity and noise figure
that HP was able to put in. Unless I want to part with the excellent
performances of this generator, which is something I don't even
consider.

SeeYa!

/\
/--\ndrea

http://www.modelberg.com
ICQ #15014472
remove NOSPAM to e-mail me
Click to expand...
There are a *lot* of op-amps that have bandwidths that exceed 550Mhz,
so with feedback or gain strapping options - depending on design, one
would be able to have an amp 0-550MHz with (i think) reasonably
comparable noise figure.
Then one would have to add a bandpass filter - say a passive one in
the input.
 
"Andrea" <andrea@modelNOSPAMberg.com> wrote in message
news:3f488f9a.651511393@news.edisontel.com...
On Sun, 24 Aug 2003 05:59:04 -0400, "Robert Morein"
nowhere@nowhere.com> wrote:

Check out The Art of Electronics 2nd Edition.
They have some listings for op-amps that go to 1 gHz.
Noise figure shouldn't be a problem for a generator.

Robert,

Thank you very much for your input, however the problem is finding the
right spare part, not doing some guesswork about how to make a patch.
I don't have the equipment to test such an endeavor or, in other
words, i would have had NO NEED TO BUY the 8640B if I had such test
equipment!

Well, check out this ebay auction anyway
Click to expand...
http://www.minicircuits.com/cgi-bin/amplifier?model=MAR-3&pix=vv105.gif&bv=4
 
Try Fair Radio Sales at fairadio@wcoil.com
that's where I got mine.
Phil J

"Andrea" <andrea@modelNOSPAMberg.com> wrote in message
news:3f47bdd8.597812979@news.edisontel.com...
Gentlemen,

A few days ago I became a (almost 100%) happy owner of a HP 8640B with
Options 001, 002 and 003. Unfortunately, this fine piece of equipment
suffered a subtle freight damage and demonstrated ZERO RF output when
checked. After some hours of work, I traced the fault to a Hybrid HP
Amplifier in the AM modulator, of which I've a photo:

http://andrea.modelberg.it/images/08640-67003.jpg

By shorting input and output of this IC I've been able to see a signal
at the output, although with reduced power and some distortion,
courtesy of the impedance mismatch. Unfortunately, all my attempts in
trying to find a replacement have been unsuccessful so far. Can anyone
point me in the right direction? All other functions seem to work just
fine, and the generator itself is in good shape and really worth the
effort to bring it back to life.

SeeYa!

/\
/--\ndrea

http://www.modelberg.com
ICQ #15014472
remove NOSPAM to e-mail me
Click to expand...
 
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