Keithley 135 4½-digit DMM. The LCD is completely ruined. Replacement with a generic LCD may be possible. Stay tuned…
Update: After obtaining a 4½-digit generic LCD, it appears that to get it to fit, the LCD and the range selector knob would have to occupy the same space. Back to the drawing board…
I must have missed this one, did you ever come close to fitting another display later on?
It looks like a good old unit, bet it was expensive in its day.
No the generic 4-1/2 LCD looked like it would take too much of a hack job to fit. These models seem to be quite rare, so getting an exact replacement is unlikely. I’ve seen some “Tegam” and “Omega” units that look like Keithley re-brands, but they were just 3-1/2 digit.
Using a scope I figured out that the rest of it is probably working.
What a dam shame, perhaps you could post dimensions and pinouts for the type of display required, someone may find a compatable 🙂
I did look through R.S, but they seemed pointless.
You could probably hack surface mount LEDs into 7 segments and still have room to for some surface mount chips to glue it to the main board.
Sounds like a serious rainy-day project!
Have you had any luck with this project?
I’ve recently got an identical Keithley 135 with the same LCD issue. It’s a shame to waste an entire functional DMM because of some crappy LCD that didn’t withstand time 🙁
I also have a Keithley 135 DMM that has a bad LCD display. Pity there is no replacement. A long time ago I ordered one from Keithley which was then supported by Fluke and they sent me a LCD for a Fluke 8020A DMM. It does not fit.
Please post if you ever find a solution.
One more to the queue… I have just found today a fleamarket Keithley 130 with a completely darkened LCD :-(. It has been just 2.50€ but it is a pity it is not useful due to the LCD.
Please, any news will be welcomed.
I purchased a new Keithley 135 (not the 135a) back in 1987 I believe. Have used this meter continuously as needed since then with no problems. Still have original brown Keithley case and leads. Surprisingly, the LCD is still as sharp and crisp as the day I bought the meter. Lucky I guess.
Have you tried peeling the polarizer film off the display glass and replacing it? It’s worth a try.. It is available online in sheet form.
I have a 135A on my bench now with some problems. When I short the leads on volts it goes close to zero but not exactly zero. If I take the leads off it wanders around 1.5v. If I change up the ranges it gives me .6v and less on the high ranges. It does measure but with some error.
Could this be a leakage problem or contamination maybe? It changes with the selected range so maybe in the switch assembly or the divider network?
I am cleaning the boards in the ultrasonic bath today. Any input would be greatly apreciated.
Thank you and have a great week!
Perhaps you can use a Omega 881F Digital Multimeter as donor