The Shop > Electronics & IC Programing

Fluke 78 multimeter

(1/3) > >>

naffsharpe (Nathan):
Can anybody tell me where (uk) can find someone to repair the above or point me to a circuit layout?
I need the Hertz function for a test but the meter seems dead. I've checked the obvious but no joy.

Nathan.

John Swift:
Hi Nathan

the user and maintenance manuals can be downloaded from Fluke
http://www.fluke.com/Fluke/uken/Support/Manuals/default.htm?ProductId=56130

do you see any thing displayed ? - see service manual page 3-8 for display test

my first test would be to try the low ohms / continuity range to see if it beeps with the input short circuited
if it beeps some of the circuit is working , no beep could indicate a problem with the power supply circuit 
 I've had  old LCD displays fail when stored in over winter in the shed !

   John

naffsharpe (Nathan):
John, many thanks for your reply. Component E1 as identified from the circuit diagram appears to be split/cracked. It looks like a capacitor outwardly but no capacitance is given on the diagram just 1500v/20% . I'll look for it online but any suggestions are always welcome !

Nathan.

naffsharpe (Nathan):
My apologies John,  in answer to your question, I have no display at all, no continuity buzzer in fact absolutely zilch! This was an expensive meter when I bought it some time in the 1990s and would love to have it working as it was - like now when I need it ! It was in daily use and then it stopped working without any warning/ apparent damage . Last general use was with the thermocouple to see how effective our heating was (last winter) inside versus outside after much draught proofing/insulating/resealing of fire box and it worked faultlessly.

Nathan.

John Swift:
Hi Nathan

looking at the circuit diagram E1 is a spark gap (SURGE PROTECTOR,1500 V,+-20%)
some I've seen looked like a  disc ceramic capacitor with a saw cut forming  the spark gap

as it looks like dead -
do you have continuity between the battery connections and each end of diode CR1 ?

then , check you have power to the IC U1
battery  +9V on pin 4 (via a diode CR2) and -9V on pin 40 (via transistor Q7 and switch S1)


   John

Navigation

[0] Message Index

[#] Next page