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Author Topic: HP 8640B  (Read 2699 times)
N1FYQ
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Posts: 5




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« on: September 22, 2005, 04:51:25 PM »

I have an HP8640B with Options 001 and 003 that I picked-up some time ago.  Although it powers-up it's not functioning.  It'd like to get it repaired but the serious test equipment service companies want tons of money to even just look at it.  Does anyone know someone who can repair these?

Thanks and 73

Gerry
N1FYQ
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WB2WIK
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Posts: 20636




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« Reply #1 on: September 23, 2005, 09:48:55 AM »

Other than "not working," what are the symptoms?

Does it "not work" on all bands?

What's the meter read if you crank the output level all the way up?  Nothing, or something?

What's the modulation meter read if you turn on AM or FM modulation and crank up the modulation level?  Nothing, or something?

Even if it reads no output, can you hear its output in a receiver, on any frequency?

The 8640B is very "modular" in design, so it can be de-bugged stage by stage.  It's mostly a UHF power oscillator followed by a bunch of frequency dividers to create the other bands, and phase-locked using a very simple PLL circuit that adjusts the voltage on a varactor which is part of the main cavity oscillator.  It ain't rocket science.  I'd first measure all the power supply output voltages to see if they're correct.  If they are, I'd then disconnect the cavity oscillator from the divider banks and see if it has any output.  If it has voltage applied and no RF output, there's the problem!

Stuff like that.

It pays to have the manual with all the schematics.

WB2WIK/6

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N1FYQ
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« Reply #2 on: September 23, 2005, 11:43:36 AM »

Hi.  And thanks for the reply.

I don't see output on any band at any output level nor can I detect any with a receiver.  When I turn on AM modulation I get a deflection of the meter that is adjustable with the AM mod controls.  It auto ranges as it should.  Nothing from FM modulation.  

I located a .pdf of the service manual and downloaded it. You've encouraged me to dive-in and try debugging it.  I suspect in the least a PS problem.  I notice the fan doesn't power-on.

Thanks for your help.  Any other suggestions greatly appreciated.

- Gerry
  N1FYQ
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N1FYQ
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Posts: 5




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« Reply #3 on: September 25, 2005, 03:11:58 PM »

Well...  it looks as though the problem is in one of the power supply boards --- no 5.2v.  Other voltages are right on.  The parent board (A17 --- the one A18 plugs into) reads a very low resistance between the TP and Gnd.  Now I just need to figure out where the problem actually resides.  Thanks for your help.

- Gerry
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VE3NUD
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« Reply #4 on: December 09, 2005, 06:26:38 AM »

where does one locate a 8640B manual for downlading as Gerry mentions?
73 Paul
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N1FYQ
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« Reply #5 on: December 09, 2005, 06:52:48 AM »

If you email me directly (gerry at a-m-i-group.com)and have an email account that can accept a large attachment (~10Mb) I'll be happy to send them to you.

73

Gerry
N1FYQ
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W9GB
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« Reply #6 on: September 27, 2006, 07:56:57 PM »

Aligent / HP does post the service manual (large Adobe Acrobat file)

http://www.home.agilent.com/agilent/redirector.jspx?action=ref&cname=AGILENT_EDITORIAL&ckey=734457&lc=eng&cc=US
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KC5-SR
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« Reply #7 on: October 24, 2007, 11:16:02 AM »

Thank you very much for posting the HP site for the manual. I downloaded it and I am in my way to troubleshoot an ill generator.
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NK4K-1
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« Reply #8 on: April 04, 2008, 04:07:28 AM »

UNFORTUNATELY, Agilent (new HP) does not supply free manuals at its web site that contain schematics.  A very good (FREE!) copy of a manual with schematics for the 8640b is found at the Boat Anchor Manual site: http://bama.edebris.com/manuals/
If you have access to wi-fi or other fast (4Mb++) connections, please use them to download, as the manual is more than 22 megabytes.
73
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