"Michael Black" wrote in message
news:alpine.LNX.2.02.1401161520120.31862@darkstar. example.org...

On Thu, 16 Jan 2014, N_Cook wrote:

Otherwise trusty meter, whenever I try on a Weston Cell it is always the
same voltage registered. But now on the ohms scale will sometimes read 10
or 12 meg with no probes in place. Good battery.
Something to do with the screen shielding? Without any metal covering, ie
the top cover removed and no replacement for the now missing sticky backed
foil over the shielded tinplate box, the meter will not pass POST, all
segments lit on display permanent and no beep on changing rotary sw
setting, normal ?.
So start with cover in place , turn to ohms, and remove cover , it goes to
the floating 10s of megs. Twizzle sticking does not show suspect switch ,
preset or anything, and gradually drifts to over-scale, 30M.
Something going leaky with age?

My DMM acted like that at one point, and I took it apart, thinking the
switch was dirty. But no.

It turned out the fuse was bad. It still had continuity, but not zero
ohms. A new fuse fixed the problem.

Michael


There is also a resistor that fuses open (fusistor) when too much current
flows. It's usually light brown or blue in color near the input jacks.
It's either 1 Kohm or 1 Megohm. It has been over 18 years since I worked on
these so all the details arn't clear. If it's blown, it will give funny
reading too. For cleaning the PCB - use electronics grade Isopropyl alcohol
and a new clean tooth brush. Scrub the board top and bottom near the input
jacks, then rinse with more alcohol and let it dry properly.

Shaun