Author Topic: Keithley 7700 Multiplexer card  (Read 663 times)

0 Members and 1 Guest are viewing this topic.

Offline MarkKruetzmann

  • Contributor
  • Posts: 18
  • Country: de
Keithley 7700 Multiplexer card
« on: November 28, 2019, 01:02:10 am »
Hi!

I am tempted to buy a Keithley 2750, but I would like to equip it with some scanner cards as well if I do. As they are quite expensive while being mostly relais and connectors, I wondered whether it would be possible to recreate the versatile 7700 by DIY means.
I did search for photos of the internals or even a schematic, but nothing came up despite a ROM dump and the relais type and manufacturer.

Is there someone with a 7700 or similar and would like to share some pictures of it, especially the used chips?

Also, it would be interesting to know which connector they use for interacting with the meter.


This question is - for now - more out of curiosity, but might be useful for future me or others. Interesting it will be anyway.


Mark
 

Offline kilobyte

  • Regular Contributor
  • *
  • Posts: 66
  • Country: de
    • My Website
Re: Keithley 7700 Multiplexer card
« Reply #1 on: November 28, 2019, 01:33:03 pm »
The 7700 uses a bunch of standard 4094 shift registers to control the relais, so noting special.
So there is no microcontroller on it but a small eeprom to store the card ID and the relay cycle counters.
there is a full Partlist in the 2700 Servicemanual, but sadly no schematic.

I have two 7700 Cards so I can take some highres photos.
 

Offline MarkKruetzmann

  • Contributor
  • Posts: 18
  • Country: de
Re: Keithley 7700 Multiplexer card
« Reply #2 on: November 28, 2019, 05:12:55 pm »
That'd be great!

Some high res photos of both sides with the chips and their markings would be very useful. And maybe detailed shots of the connector and sizes of everything.
 

Offline kilobyte

  • Regular Contributor
  • *
  • Posts: 66
  • Country: de
    • My Website
Re: Keithley 7700 Multiplexer card
« Reply #3 on: November 28, 2019, 07:58:52 pm »
Here are some pictures of the 7700 card.

Because the card doesn't use any microcontroller or some other special parts it should be possible to design a DIY Mux Card.
I only had the PCB rules at hand so maybe I can measure some dimension at the weekend.

 
The following users thanked this post: thm_w

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 8280
  • Country: de
Re: Keithley 7700 Multiplexer card
« Reply #4 on: November 28, 2019, 08:36:11 pm »
Somewhere in the thread about the DMM6500 there is some extra info and AFIAR even hints on a DIY solution. I am however not sure if the cards are the same.
 

Offline thm_w

  • Super Contributor
  • ***
  • Posts: 2421
  • Country: ca
Re: Keithley 7700 Multiplexer card
« Reply #5 on: November 28, 2019, 10:35:30 pm »
Somewhere in the thread about the DMM6500 there is some extra info and AFIAR even hints on a DIY solution. I am however not sure if the cards are the same.

Yes but that is 2000-SCAN, I asked user cozdas to create a thread with more info on the DIY build but have not heard a response back.

https://www.eevblog.com/forum/testgear/new-keithley-dmm6500/msg2401032/#msg2401032
https://www.eevblog.com/forum/testgear/new-keithley-dmm6500/msg2564241/#msg2564241
 

Offline MarkKruetzmann

  • Contributor
  • Posts: 18
  • Country: de
Re: Keithley 7700 Multiplexer card
« Reply #6 on: November 29, 2019, 08:47:16 am »
Dang, it's a four layer jobby! Well, with an installed ROM and the shift registers in place, it would still be possible to recreate all the switching and, hence, the schematic.

The connector apparently is a Pancon 130-332-523 (obviously), which is no longer available (sadly). It is, however, designed after DIN 41612 and there are manufacturers producing similar substitutes (thankfully). One might need to rip out the inner connector row, however, as I did not find yet a 32-pole connector with 3 rows, where the inner row is not used. I found this though:
https://www.mouser.de/ProductDetail/HARTING/09282486804791?qs=sGAEpiMZZMud62t8luTOJjrQXusuevCyur2NPCEHnCLKUNNf9%2FwINw%3D%3D
Also from a respectable german manufacturer (thank you, Keithley, for thinking of us Krauts), should fit mechanically, it might just have a lower insulation spec then when assembled on the PCB due to the lack of clearance.
So, with this part one might be able to recreate something with worse specs.

The project will clock in at around 100$ though as especially the relais are quite expensive.
https://www.mouser.de/ProductDetail/KEMET/EE2-3SNUH-L?qs=BenOyfdfArr1F1eFnWGDbw%3D%3D
The case would be printed in most cases (ha!) I assume.

I'm just wondering: The functionality of the shift registers could be implemented by a microcontroller. This way it can be reconfigured without spinning a new board.
 

Offline Ice-Tea

  • Super Contributor
  • ***
  • Posts: 2155
  • Country: be
    • Freelance Hardware Engineer
Re: Keithley 7700 Multiplexer card
« Reply #7 on: November 29, 2019, 10:27:52 am »
Think you should go bigger.

Much bigger.

[attachimg=1]

Yeah, that's mine  ;D
 
The following users thanked this post: radhaz


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf