Author Topic: Wavetek DM27XL No display  (Read 1994 times)

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Offline Steve1851Topic starter

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Wavetek DM27XL No display
« on: June 23, 2019, 12:50:07 am »
Hello everyone.
I have a Wavetek 27XL multimeter with no display. I was wondering if anyone out there is familiar with the UM7108F chip. On pins 5 & 6 there is a crystal that doesn’t seem to be oscillating. Does anyone know what the function of this particular clock circuit  is?
The clock on pins 41, 42, and 43 is working.
The clock input on pin 36 is not connected. Just as the print  shows.
This is the closest print I can find:   https://320volt.com/wp-content/uploads/2011/05/Unit-UT70A-UT70A-schema-UT70A-circuit-Digital-MultiPurpose-Meters.gif
Thanks for your help in advance.
Steve
 

Offline Steve1851Topic starter

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Re: Wavetek DM27XL No display
« Reply #1 on: June 23, 2019, 05:48:01 pm »
The correct model is Wavetek 27XT. Sorry for the wrong model.
From the Data sheet I can't tell if the LCD frequency's come from the clock input on pin 5 and 6 or the other clock input. Is anyone out there familiar with the UM7108F DMM IC?
 

Offline retiredcaps

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Re: Wavetek DM27XL No display
« Reply #2 on: June 24, 2019, 02:38:21 am »
This thread and the links within it might give some clues?

https://www.eevblog.com/forum/testgear/broken-wavetek-dm27xt/
 

Offline Steve1851Topic starter

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Re: Wavetek DM27XL No display
« Reply #3 on: June 28, 2019, 05:00:47 pm »
The prior thread provided no help. I couldn't find anything on the web to answer this question. However, to answer my own question, the crystal oscillator does provide the signals to "excite" the LCD. Without it working you will get random segments, some lit and some not.
 


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