[Test-Equipment] HP 8640B Broken AM Modulation Switch

[Glenn Little]

There are three ways to repair this that I know of.
The most reliable is to replace the mother board.
The next most reliable is to repair the broken 
switch lever, if the rest of the switch is ok.
The last method is to replace the switch.
This may require removing the mother board,it has 
been a long time since I repaired one.
The switch contacts are etched and gold plated on the mother board.
The switch actuator (the piece that is broken) 
has metal pieces that are in the plastic that do the actual switching.
The switch actuator is held to the mother board 
(IIRC) by a metal frame that is riveted to the mother board.
This is easy for assembly, with the proper tools 
and jigs, but, difficult to correctly repair.

Hope this helps and is not too confusing.

If this is the only 8640 that you have you will 
have a difficult, but not impossible repair ahead.
If you can find another 8640 to get the mother 
board out of, the repair is relatively straight forward.

73
Glenn
WB4UIV




At 12:36 PM 11/19/2014, you wrote:
>I've done it before. It took quite some time to 
>locate a donor switch, finally got one from a 
>hangar queen 8640 that a friend of mine had, 
>they are not easy to come by because they are 
>often broken and are in big demand. Locating one 
>is half the battle, installing it is a miserable 
>job. I would not want to have to do it again. 
>Mark WA1QHQ      On Wednesday, November 19, 2014 
>11:56 AM, Pete Lancashire 
><pete at petelancashire.com> wrote:    Does the 
>switch it self still work ? If so I've in the 
>past fabricated and then epoxied a new piece. 
>Did it for one of the HP pulse generators that 
>used the same design switch. Maybe ask on the 
>Yahoo Agilent/HP group. -pete On Wed, Nov 19, 
>2014 at 8:18 AM, Barry <n4buq at knology.net> 
>wrote: > Anyone have any suggestions on how to 
>fix a broken AM modulation switch on an HP 
>8640B?  I'm looking at one that has that 
>problem on eBay and was wondering how hard it is 
>to find a replacement part.  I know these are 
>fragile points and many have been broken over 
>the years.  I'm also figuring there are few if 
>any NOS replacement parts so not sure if I want 
>to take a chance on this or not so was was 
>wondering what others have done for this.  Time 
>for a 3D printer? > > Thanks, > Barry - 
>N4BUQ > > 
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