[Test-Equipment] HP 8640B Final Amplifier Replacement??

[jbarnes]

Hi,
I was looking at this situation a few days ago. I have an HP8640A with a blown output hybrid.

I found another page on this subject. Have a look at:

http://montevideocomputers.com/ham/projects.html

About halfway down the page is a section on the HP8640B amplifier.

The writer, Tim WB0RXX, suggests that there is also a detector circuit in the hybrid. He also reports problems when using the MMICs from Sirenza. He says that MMICs get destroyed when the step attenuator is adjusted, due to high SWR. 

Tim presents an amplifier based on a single transistor.

It might be a good idea to use a low voltage supply as suggested by VE7CA, at:

http://www.shelbrook.com/~ve7ca/Tst864.htm

It seems that the avionics version of the 8640B doesn't need/use the detector. I have to confirm this.

I haven't done any experiments yet. I am just presenting information that I found during searching.


Regards,

John Barnes





---------- Original Message ----------------------------------
From: "Steve Harrisonusa" <k0xp at dandy.net>
Date:  Mon, 26 Feb 2007 15:09:00 -0500 (EST)

>> Hello!
>>
>> There is some hope :-)
>>
>> http://www.shelbrook.com/~ve7ca/Tst864.htm
>
>Has anybody actually used a MAV-11 as a replacement final amplifier??
>
>I'll hafta drag out my spectrum analyzer tonight, fire it up and see
>whether it still works, then do some measurements on the one 8640 I have
>with a good final, then try a MAV-11. I also have several Moto hybrid amps
>but nothing specified to cover the whole range of 0.4 - 550 MHz. The ones
>now available are speced only 5 - 200 MHz, with no info as to their
>rolloff at the ends of their range.
>
>A single MAV-11 driving a pair in parallel might work fine, I'll hafta see.
>
>Thanks,
>SteveH
>
 




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