Author Topic: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)  (Read 1393 times)

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Offline douardda

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Hi,

I am trying to repair a venerable HP 8662A Signal Generator. No need to make the presentations of the generator I guess.

During my repair, I noticed that two key springs were missing. Unfortunately, these key buttons are very hard to find now. Or at indecent price.

Fortunately, I found one of the missing springs in the enclosure, but only one. So I had to find a solution for the missing one. And while I was waiting for a quotation from a local spring manufacturer, I had the idea to try to use some packaging plastic and cut a poor-man's spring in that. I tries several widths, and found one that seems to work just fine. The feeling is a bit softer than the other keys, but overall, it works very nicely. Not sure it will last a long time, but hey.




Just in case, might help.

If someone is interested in the repair of the generator itself (for which I had several issues with the PSU and the LF section), I am writing a series of blog posts on https://whatever.sdfa3.org/hp8662a-synthetized-signal-generator-part-1.html

David
 
 
 

Offline lowimpedance

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #1 on: April 23, 2018, 01:24:05 am »
Neat fix  :-+. And if it doesn't last long, (although I'll bet it will,) cut another !.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline xrunner

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #2 on: April 23, 2018, 02:02:44 am »
That's a very interesting idea. I've had issues with those before, and went in and flipped over every one of the steel springs to get them to react better after so many years. It's ideas like this that make this forum a very special resource.  :-+
I am a Test Equipment Addict (TEA) - by virtue of this forum signature, I have now faced my addiction
 

Offline KE5FX

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #3 on: April 23, 2018, 02:24:57 am »
(from blog) Carrying the unit from my cellar to my appartement was some kind of a job: it's a robust 30kg device I had to climb the 7 levels: no lift in the old parisian building I live in...

That's nothing short of Herculean.  :o   8662As are heavy.

From your photos, it looks like someone has already replaced at least one of the capacitors on the power supply transformer PCB (A7?), but don't forget to check the ESR of all of them, especially the capacitive voltage divider.
 

Offline VK5RC

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #4 on: April 23, 2018, 05:45:40 am »
I got some clock spring off flea bay for some of my HP iron "clacky HP switches", I found the 2 thou of inch or 0.05mm clock spring steel works well. Trimming it is the hard part.
see also http://www.rbarrios.com/projects/hpswitch/      re this problem as well

7 stories with an HP 8662A, you must be fit!

For some other classic repair ideas there is a sticky topic - includes some ideas from KE5FX, Xrunner and others  https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/msg592523/#msg592523
I have added yours to it  after a 'heads up' by xrunner- Thanks
« Last Edit: April 23, 2018, 05:55:47 am by VK5RC »
Whoah! Watch where that landed we might need it later.
 

Offline basinstreetdesign

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #5 on: April 23, 2018, 05:54:25 am »
Good one!   :-+
STAND BACK!  I'm going to try SCIENCE!
 

Offline eb4eqa

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #6 on: April 23, 2018, 07:06:32 am »
Yep, I was going to recommend also my own mini-article http://www.rbarrios.com/projects/hpswitch/, thanks Robert.

 It is an easy fix, you will get it back in working order quickly.

Regards,
Roberto EB4EQA
 
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Offline douardda

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #7 on: April 23, 2018, 04:56:50 pm »
(from blog) Carrying the unit from my cellar to my appartement was some kind of a job: it's a robust 30kg device I had to climb the 7 levels: no lift in the old parisian building I live in...

That's nothing short of Herculean.  :o   8662As are heavy.

Yep that was a pain in the neck. Once upstairs, took me 15mn to recover :-)

From your photos, it looks like someone has already replaced at least one of the capacitors on the power supply transformer PCB (A7?), but don't forget to check the ESR of all of them, especially the capacitive voltage divider.

Yes, the unit has been repaired several times I think. There are several evidences of repairs, and there is also an Agilent sticker somewhere on a board.

David
 

Offline douardda

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Re: Quick Fix: my 2c. fix for HP button key (in this case: HP8662A)
« Reply #8 on: April 23, 2018, 04:59:36 pm »
I got some clock spring off flea bay for some of my HP iron "clacky HP switches", I found the 2 thou of inch or 0.05mm clock spring steel works well. Trimming it is the hard part.
see also http://www.rbarrios.com/projects/hpswitch/      re this problem as well

Yep, I was going to recommend also my own mini-article http://www.rbarrios.com/projects/hpswitch/, thanks Robert.


Yes I've seen this website and video, thanks.

For some other classic repair ideas there is a sticky topic - includes some ideas from KE5FX, Xrunner and others  https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/msg592523/#msg592523
I have added yours to it  after a 'heads up' by xrunner- Thanks

Thanks, I missed this topic (so much going on the eevblog forum, it's hard to track).

David
« Last Edit: April 23, 2018, 05:01:28 pm by douardda »
 
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