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HP 8640B - Need Help!

A

Andrea

Jan 1, 1970
0
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
 
R

Robert Baer

Jan 1, 1970
0
Andrea said:
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

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?
 
A

Andrea

Jan 1, 1970
0
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
 
F

Fred Abse

Jan 1, 1970
0
Noise figure shouldn't be a problem for a generator.

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.
 
F

Fred Abse

Jan 1, 1970
0
Fred,

'nuff said! I could have said that word by word. Except for my name,
that is :>

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 :)
 
R

Robert Baer

Jan 1, 1970
0
Andrea said:
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.


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

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.
 

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