Products > Test Equipment
Modding a Keithley 197
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akabek:
I just realized I had the wrong model number mentioned.  I have the 197a.

I was looking at those EL panels.  Were you able to cut yours to size?  I thought I read somewhere the panel in your link could not be cut.

Is your Keithley a 175a?  I wonder if the driver may be the issue.  To be honest I am not sure how bright the backlight should be in a 197a.
don.r:
Never got to the stage of cutting since I discovered it was the driver. Mine was a 175A. Measure the voltage going into the panel. It should be somewhere between 70 and 90V (AC?). Mine was 25V. I used a driver similar to this but not sure what the input voltage was (12V or 5V): https://www.aliexpress.com/item/1005001977407178.html
akabek:

--- Quote from: don.r on February 03, 2021, 05:10:26 pm ---Never got to the stage of cutting since I discovered it was the driver. Mine was a 175A. Measure the voltage going into the panel. It should be somewhere between 70 and 90V (AC?). Mine was 25V. I used a driver similar to this but not sure what the input voltage was (12V or 5V): https://www.aliexpress.com/item/1005001977407178.html

--- End quote ---

Excellent, I will do some checking tonight.
akabek:
I checked the AC voltage going into the backlight panel and it is 44.8v.  Just curious how you know the AC voltage should be between 70 and 90v?  Were you able to locate the schematics for the 197a? 
don.r:

--- Quote from: akabek on February 04, 2021, 12:21:33 am ---I checked the AC voltage going into the backlight panel and it is 44.8v.  Just curious how you know the AC voltage should be between 70 and 90v?  Were you able to locate the schematics for the 197a?

--- End quote ---
Can't remember where I saw the voltage but I think it was the standard of EL panels. They light at 50V and get brighter as voltage increases. Mine was the 175A and has schematics in the user manual. I think the feed voltage to the driver circuit could have been 5V but you can measure that. Its the black box on the back of the front panel.
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