Keithley 197A dmm - Page 1
Forum section: electronics / general

author: triac
author_rank: Contributor
timestamp: August 25, 2014, 01:52:37 am
content: WTB LCD display module for Keithley 197A DMM.Anybody who has a non working or broken down unit, would appreciate this.Triac.

author: ModemHead
author_rank: Frequent Contributor
timestamp: August 25, 2014, 02:42:44 am
content: I just acquired one of those. It was working except for some contrast problems with the LCD. Cleaning the elastomeric connectors and increasing the clamping pressure with a bit of tape restored the display. It's a very nice unit. What happened to your display?

author: triac
author_rank: Contributor
timestamp: August 25, 2014, 12:31:39 pm
content: The bottom row of LCD bars do not work, not a contact problem i have cleaned all of them.It looks as though the multiplexed drive is defunct on that line, this is a sealed chip so not repairable.Everything else is OK so I thought some one might have parts from a 197 that had been given up as non repairable.Triac.

author: idpromnut
author_rank: Unknown
timestamp: August 25, 2014, 03:03:47 pm
content: Hmm, I have a project on the back burner to re-engineer the display used in my 175A (model below yours); I wonder if both use the same display board?

author: triac
author_rank: Contributor
timestamp: August 26, 2014, 05:20:51 am
content: The 175A is a 4.5 digit display the 197A is a 5.5 digit display, not compatible.

author: idpromnut
author_rank: Unknown
timestamp: August 28, 2014, 05:42:25 pm
content: Quote from: triac on August 26, 2014, 05:20:51 amPretty sure it's just the LCD that is different. Also, my project involved ditching the LCD for an OLED-based display.

author: triac
author_rank: Contributor
timestamp: August 29, 2014, 03:44:17 pm
content: That is interesting,looking at the 175 & 197 display dwgs they do have the same 7225 chips. Inputs to the 7225 are the same but am not sure the output tracks to the lcd would match, Ihave not had a 175 to take apart and compare.They must have built the 175 with a view to upgrading to a 195.The chip on my board is covered with a blob of black epoxy so it is not replacable. Allthough a 7225 mounted in a daughter board and hack into the traces with some hard wiring would work so long as trace identification could be done.is the chip in the 175 covered with epoxy also, you will have to identify them for your coversion. If you have identified them I would like to get a sketch from you as to there orentation.How far along with the Led conversion are you? It sounds like a good idea , are you feeding the output of the7225 to cmos led driver chips?Triac

author: idpromnut
author_rank: Unknown
timestamp: October 24, 2014, 11:46:05 pm
content: Sorry for the tardy reply; my project involves actually replacing the entire display PCB (including the display IC) and decoding the command set for the 7225 using a micro (which would also drive the OLED display). I hadn't got very far because I was stuck with only smaller OLED displays to work with, but have since got my hands on a larger (width-wise) display and will probably jump back into it if there's some interest. But this would be a complete PCB replacement for the display board in the 175 (and perhaps the 197).