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Old 15th Sep 2020, 10:33 pm   #1
Jon_G4MDC
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Default HP Switch Rotor Contacts

Looking for the spring 4 finger contacts that were used on switch rotors of HP8558/9 Spectrum Analysers.

Quite possibly much other HP gear from the Mid 1970s' through the 1980's but I know them from these models.

If anyone has some contacts (or even complete switch rotors contacts attached or detached / included with) I would be very pleased to discuss please.
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Old 16th Sep 2020, 7:09 am   #2
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Default Re: HP Switch Rotor Contacts

Am pretty sure this subject has come up before here and over on the EEVblog forum. If I remember correctly the consensus was "rarer than unicorn toenail clippings"

Andy.
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Old 16th Sep 2020, 7:47 am   #3
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Default Re: HP Switch Rotor Contacts

I think so too but let's see.
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Old 16th Sep 2020, 1:13 pm   #4
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Default Re: HP Switch Rotor Contacts

Hmm, i used to be a sony camera engineer and this type of wiper was used a lot in the zoom/focus tracking systems of some of their lenses, i might be able to call in a favour and get one for appraisal if nothing turns up and it may still have to be adapted to fit but, it's a possibility.
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Old 16th Sep 2020, 1:14 pm   #5
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Default Re: HP Switch Rotor Contacts

Hi Jon,

Any chance that such fingers could be "fashioned" from RF shields?
I would certainly look into that!
https://duckduckgo.com/?t=canonical&...ages&ia=images

Regards, Peter
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Old 16th Sep 2020, 2:21 pm   #6
Jon_G4MDC
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Default Re: HP Switch Rotor Contacts

I am prepared for finding that make your own is the only way.
I have a few ideas on that front but whatever happens it needs to be a perfect job.

It would be worse to make some poor contacts that only ruin the printed traces instead.
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Old 16th Sep 2020, 2:37 pm   #7
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Default Re: HP Switch Rotor Contacts

Were they made in house, if not there must be a legacy manufacturer somewhere.
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Old 16th Sep 2020, 5:57 pm   #8
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Default Re: HP Switch Rotor Contacts

I passed on my last HP rotors of this type last year. But I'll have a look elsewhere where there may be a scrap chassis.
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Old 16th Sep 2020, 6:21 pm   #9
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Default Re: HP Switch Rotor Contacts

Most divisions had their own toolrooms making press tools for sheet metal parts. RFI contact finger stock was bought in because it was an off the shelf commercial product.

If I needed to make some contact strips like that, I'd worry about finding a source of the right sheet material, a beryllium copper with something like silver plating. Then I wouldn't try to make the part itself, but to make a little press tool to cut them.

As plan B there are firms doing photochemical etching/machining who can make intricate shapes in all sorts of sheet materials and contact strips are nothing new to them. Some tooling to shape it from the flat will be needed.

In days gone by, I could have whistled up the drawings for each component part, phoned the people who did them etc etc. Grrr!

David
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Old 16th Sep 2020, 7:28 pm   #10
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Default Re: HP Switch Rotor Contacts

Ah yes - very many thanks to all - exactly so!

I have been loooking at the finger stock of the usual suspects. No match so far...

I'm ready for doing photo-etch or laser blasting. The 2D CAD for it is done as a simple flat item.
I have also recently acquired a small scale milling capability - I just don't fancy doing it at the present skill level.

If they were done by an etch/blast house, how many to commission? They would come back as a flat sheet with breakout tabs.
Would anyone else want any? To finish myself, by hand, or to give the supplier a 3D CAD model and say finish them all?

It seems to me they are some stainless steel but of course a plated Beryllium Copper was also in mind.

Pity you lost that info store David! Now you make me wonder did I look at RFI finger stock in enough detail?

Really hoping this does not break any forum rules. We need these.

So many questions, so much running about Mr Bond...

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Old 17th Sep 2020, 12:19 am   #11
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Default Re: HP Switch Rotor Contacts

Those contacts were almost certainly custom parts.

The other nasty little switch throughout a lot of HP gear is the Bill West switch, a little red plastic clicker that works on gold plated pads on a board. I suppose a tact switch soldered on and some artful high-res 3D printing might handle these.

The archive was HP's, I worked there. Most of it gone now in the Santa Rosa fires a few years ago.

David
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Old 17th Sep 2020, 9:54 am   #12
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Default Re: HP Switch Rotor Contacts

Jon, do you remember the Pye P5000 series batteries? They had a row of gold plated sprung tabs. A lot bigger, but whether you had one and might be a source of material to see if it could be trimmed?
There is also a mini "centronics" type connector with gold plated individual tabs.
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Old 17th Sep 2020, 11:29 am   #13
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Default Re: HP Switch Rotor Contacts

Quote:
Originally Posted by Jon_G4MDC View Post
.. how many to commission?
Would anyone else want any?
Yes please! Put me down for two sets. If the price is ok for you it will be ok for me
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Old 17th Sep 2020, 1:34 pm   #14
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Arrow Re: HP Switch Rotor Contacts

There are several entries on the Internet that deal with this problem - and other common faults. A typical fix for missing wipers is to use contactors from relays.

Al.
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Old 17th Sep 2020, 1:41 pm   #15
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Default Re: HP Switch Rotor Contacts

Haven’t looked into dimensions but I’ve recently scrapped a damaged HDMI connector and they have lots of springy gold plated contacts.
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Old 17th Sep 2020, 5:21 pm   #16
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Default Re: HP Switch Rotor Contacts

The stock is 5 thou (0.127mm) thick whatever it is.

The width of each set of 4 fingers is 0.25" the overall length is ~0.5" maybe plus a bit to allow for the curved ends to the fingers.
Each finger is 50thou wide. This was made in a land of imperial measurements!

I think making them will be the only way to go unless someone has a scrapped unit. My whole reason for being bothered is exactly that I don't want to scrap a unit.

It's a shame the HP archive is lost since it could answer the question about what is the raw material. I expected BeCu or something like it but I have come around to thinking it's stainless. It is shiny silver/grey and by filing you don't hit base metal of a different colour.
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Old 17th Sep 2020, 5:26 pm   #17
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Default Re: HP Switch Rotor Contacts

Great if it's stainless, you can buy that in all sorts of thicknesses as 'shim stock'

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Old 17th Sep 2020, 5:36 pm   #18
Jon_G4MDC
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Default Re: HP Switch Rotor Contacts

Trouble is it's a broad church. There are so many SS grades to choose from.
All I know is it's not magnetic so it's not a ferritic stainless steel.

Wondering how to choose. Maybe ask the suppliers who can etch or laser blast what they recommend or what they stock. I think that will have to be next move.
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Old 17th Sep 2020, 6:27 pm   #19
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Default Re: HP Switch Rotor Contacts

Often used in cheap DMMs, get one and examine?
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Old 17th Sep 2020, 8:15 pm   #20
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Default Re: HP Switch Rotor Contacts

Quote:
Originally Posted by Radio Wrangler View Post
Those contacts were almost certainly custom parts.

The other nasty little switch throughout a lot of HP gear is the Bill West switch, a little red plastic clicker that works on gold plated pads on a board. I suppose a tact switch soldered on and some artful high-res 3D printing might handle these.

The archive was HP's, I worked there. Most of it gone now in the Santa Rosa fires a few years ago.

David
Side issue - if anyone wants any of the Bill West switches, top half, I've got a load of spare ones which were pulled from something that they weren't melted to the board in!
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