Keithley 7700 Multiplexer card - Page 1
Forum section: electronics / testgear

author: MarkKruetzmann
author_rank: Contributor
timestamp: November 28, 2019, 01:02:10 am
content: 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

author: kilobyte
author_rank: Regular Contributor
timestamp: November 28, 2019, 01:33:03 pm
content: 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.

author: MarkKruetzmann
author_rank: Contributor
timestamp: November 28, 2019, 05:12:55 pm
content: 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.

author: kilobyte
author_rank: Regular Contributor
timestamp: November 28, 2019, 07:58:52 pm
content: 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 28, 2019, 08:36:11 pm
content: 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.

author: thm_w
author_rank: Super Contributor
timestamp: November 28, 2019, 10:35:30 pm
content: Quote from: Kleinstein on November 28, 2019, 08:36:11 pmYes 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/#msg2401032https://www.eevblog.com/forum/testgear/new-keithley-dmm6500/msg2564241/#msg2564241

author: MarkKruetzmann
author_rank: Contributor
timestamp: November 29, 2019, 08:47:16 am
content: 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%3DAlso 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%3DThe 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.

author: Ice-Tea
author_rank: Super Contributor
timestamp: November 29, 2019, 10:27:52 am
content: Think you should go bigger.Much bigger.Yeah, that's mine

author: pmurray4
author_rank: Contributor
timestamp: June 03, 2022, 04:36:19 pm
content: Did anyone reverse engineer the 7700 card in the end? or does anyone know where I can find the schematics? I had a card that no longer detects in the DAQ6510 (I have 2 other cards that work fine). I attempted to read the EEPROM using an Arduino setup (Didn't have my chip programmer at hand) and realized that I wiped the EEPROM on the faulty card and one of the good cards. The weird thing is that good card that I wiped the EEPROM still works as normal. I'm assuming it has no checksum to validate the data.I'm working on reverse engineering it myself in the meantime as I need to know why it's not detecting

author: coromonadalix
author_rank: Super Contributor
timestamp: June 03, 2022, 09:32:35 pm
content: https://www.ebay.com/itm/115291704034?for sale ??

author: pmurray4
author_rank: Contributor
timestamp: June 06, 2022, 05:31:40 pm
content: $200 is better than $1000 but still pricey.The one EEPROM was corrupt, I copied the good EEPROM's contents to it and it still doesn't detect the card, so definitely not the EEPROM. But it definitely does store the serial number of the card in there.