UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Closed Thread
 
Thread Tools
Old 3rd May 2019, 11:22 am   #1
John_BS
Octode
 
John_BS's Avatar
 
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,757
Default HP 1980's test equipment keyboard issues

I've been working on an HP3577A network analyser (bought at auction / dead display). I've now got the display back working, but the keyboard is very flaky. I wondered if anyone has experience of tackling the keyboard-switches: is it the usual contact cleaner solution or something more drastic?

John
John_BS is offline  
Old 3rd May 2019, 1:07 pm   #2
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
Default Re: HP 1980's test equipment keyboard issues

Do you have a picture of the keyboard switches used? I have various HP ones floating around somewhere from some HP kit I trashed for the enclosure as it was BER.
MrBungle is offline  
Old 3rd May 2019, 1:28 pm   #3
John_BS
Octode
 
John_BS's Avatar
 
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,757
Default Re: HP 1980's test equipment keyboard issues

I've just this minute removed the keyboard (what a job!).

I've a horrible suspicion that these use the top-side gold tracks as part of the switch contacts? The stainless strip which is visible seems to be the spring which "snaps" and returns the key to rest position.

John
Attached Files
File Type: pdf HP switches.pdf (408.9 KB, 61 views)
John_BS is offline  
Old 3rd May 2019, 1:31 pm   #4
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: HP 1980's test equipment keyboard issues

They are called Bill West switches

The stainless steel snap-spring provides the action an a gold plated leaf contacts gold plated pads on the board.

All assembled by heat staking

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 3rd May 2019, 2:01 pm   #5
John_BS
Octode
 
John_BS's Avatar
 
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,757
Default Re: HP 1980's test equipment keyboard issues

Many thanks David.

OK: so how to clean them? "Wash" the whole board with isopropyl?

John
John_BS is offline  
Old 3rd May 2019, 2:07 pm   #6
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
Default Re: HP 1980's test equipment keyboard issues

Interesting. Not the ones I have. The ones I had were fixed on with a metal bar over the top rather than melted in situ.
MrBungle is offline  
Old 3rd May 2019, 3:26 pm   #7
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: HP 1980's test equipment keyboard issues

Isopropyl is probably OK.

Trike used to make them brittle

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 3rd May 2019, 4:14 pm   #8
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
Default Re: HP 1980's test equipment keyboard issues

'Back in the day' (and maybe still) HP would not supply them as spare parts. They would replace individual switches if you sent the PCB to a service centre, but they felt that most repairers could not do a proper job of the heat staking with the tools they had available.
TonyDuell is offline  
Old 3rd May 2019, 5:11 pm   #9
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: HP 1980's test equipment keyboard issues

Oddly, I did quite a few on instruments I was working on, on my bench without any special tools other than a turned-down weller soldering iron bit. The trick was to just turn the iron on for long enough to get the right temperature. The right temperature being found by melting a bit of the old switch. Being in an HP plant, we had raw switch parts in stores.

I suspect the problem these days is the gold's worn through.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 3rd May 2019, 8:18 pm   #10
John_BS
Octode
 
John_BS's Avatar
 
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,757
Default Re: HP 1980's test equipment keyboard issues

I took the bull by the proverbial horns and flooded the switches/board with neat Isopropyl (over a large bowl), whilst giving each switch a good bit of exercise. Then blew out the excess alcohol with compressed air and gave it a second do. After drying and putting everything back together it seems to have done the trick: pretty much perfect responses from the keys.

Now to try to sort out why the log sweep has an abrupt 7dB amplitude step as it passes thro 100kHz (not present with a linear sweep: is there a change in RBW filter around 100kHz??)

This one could run & run!
John

PS I suspect this instrument spent a couple of decades in a lab together with smokers...
John_BS is offline  
Old 3rd May 2019, 9:12 pm   #11
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: HP 1980's test equipment keyboard issues

Probably RBW switching. You should see a step in the noise floor, but the scaling of normal signals should be right at all frequencies. The apparent level of noise-like is dependent on the bandwidth being simultaneously detected.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:56 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.