Simpson 360-2 DVM problem

Manuals and schematics. Some troubleshooting info included:

Inputs are usually protected by fuses, and overrange readings might mean the fuse is bad. Meter failures also result from dirty/broken switches, worth checking. (always check the obvious things first).

The last time a meter failed on me, it was a speck of something conductive shorting the selector switch.

First thing to check is the power supply voltages. If those are all OK, then the next thing to suspect is the A-D converter, since it appears to be the most obvious common component. From the parts list, it's a custom LSI part. If it is a relabeled A-D chip, then it might be possible to locate a replacement. You'll have to research the pin functions and try to identify a standard part that matches. If it really is a custom Simpson part, then Simpson is probably the only source. Don't know how long the 360-2 has been out of production, but it's highly unlikely that the part is still available.

Cheers!

...and some details on the Simpson 360-2:

(4.5MB) The manual has a schematic and parts list.

My rule-de-thumb for such old hardware is "if it moves, it breaks". As suggested, check the power supply voltages. After that, clean the slide and rotary switch contacts. My guess(tm) is that the output of the input ampflifiers (IC101 and IC102 are pegged to one or other rail, thus causing the over-range indication.

I'd certainly check the simple stuff first; the fuses and low value resistors. Next comes power supply as someone else suggested. Anything too much more than that is probably unecessary and unproductive - you can replace your 360-2 with another from eBay. Prices vary but you can almost always get one with it's power adaptor for under 50.00.

Mark Z.

Mark Z.

Steve-

How much over range? Many old VTVMs had a resistor in its probe. If you used a probe with no resistor, readings would be a bit high.

You might research the Simpson 360-2 to see if it happened to require a similar probe.

Fred K4DII