Looking for Keithley 177 DMM Schematic. - Page 1
Forum section: electronics / testgear

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: February 10, 2014, 10:57:46 pm
content: Hi group,I am looking for a nice, readable, schematic for the Keithley 177 DMM.I have found the one on the Keithley website that is complete, but barely readable.I found another one which was very readable, but only half the schematic.I have one of these for repair.Many thanks !!Jay_Diddy_B

author: wiss
author_rank: Frequent Contributor
timestamp: February 10, 2014, 11:06:06 pm
content: Register at keithley.com and download it from there?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: February 11, 2014, 12:11:25 am
content: Wiss,Thank you for the reply. I have registered with Keithley and downloaded the manual. This is where I got the one with unreadable schematics. The file size is 2740kB (according to Windows).Here is a sample of the schematic:Thanks,Jay_Diddy_B

author: wiss
author_rank: Frequent Contributor
timestamp: February 11, 2014, 01:02:18 am
content: Sorry, a bit quick to reply...You only need the scematics? I can see if there are any at work...

author: wiss
author_rank: Frequent Contributor
timestamp: February 11, 2014, 08:58:18 am
content: I did find a 177 so there is a reasonably high probability that the manual is somewhere in the building, the person responsible for it is not here until Thursday, I`ll ask then.

author: wiss
author_rank: Frequent Contributor
timestamp: February 13, 2014, 09:07:56 am
content: No luckIt might be somewhere but it will take a large amount of time to locate it...

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: February 13, 2014, 01:11:39 pm
content: Wiss,Thank you very much for your efforts.I will try and fix the meter with the schematic in the manual that I have.Jay_Diddy_B

author: MBY
author_rank: Regular Contributor
timestamp: February 17, 2014, 02:32:45 pm
content: I had exactly the same problem trying to fix my Keithley 177 and building a RS232 interface for it. I ended up with trying to recreate the schematics and after many hours I got what I suspect is a accurate redraw.Hope it helps! I cannot guarantee that every connection I've drawn is correct, but I succeeded both in fixing my DMM and to create a RS232-interface using a AVR.I hope its not the power supply that is the problem in your case. I redraw almost all BUT the power supply, since it worked ok for me.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: February 17, 2014, 04:01:58 pm
content: MBY,Thank you for providing the re-touched schematic. I found a manual here:http://exodus.poly.edu/~kurt/manuals/manuals/Keithley/KEI%20177%20Instruction.pdfThis manual is little cleaner than the manual from the Keithley website. Unfortunately it contains only half of the schematic. It does include the power supply section. I have attached the pdf with the power supply section.I have three of these meters that I got in a package deal with a 175, 197 and three 177. None of the working.All of them, except one of the 177 are repaired.The two 177 had dirty switches, I cleaned the switches and then cleaned the board. The remaining 177 has a bad ICL71C03, the main chip.Thank you again!!Regards,Jay_Diddy_B

author: lowimpedance
author_rank: Super Contributor
timestamp: February 18, 2014, 02:52:38 am
content: Just to note that the RACAL DANA 4003 DMM is a rebadged Keithley 177.On ebay there is a seller 'teoulet' (Tucker electronics) selling manuals and they have currently a listing for the 4003 manual, which in the photo is the main schematic and P/S schematic.They are actually quite readable so you can "re touch" your crummy copy if any part of it is not readable!!.Look for 'DANA manual 4003 '!. and see what I mean.I have a 4003but alas I do not have the handbook, and also have to get by with the awful copy as well.EDIT Aug 2018I did find a 177 manual and have uploaded a decent copy of the schematic and part layout in this thread ;https://www.eevblog.com/forum/repair/keithley-177-power-supply/

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: February 18, 2014, 03:20:36 am
content: Hi,Here is the schematic picture from the teoutlet listing.Regards,Jay_Diddy_B