Simpson Model 360-2 Digital Multimeter
This meter is a good example of why I now seldom buy any vintage electronics from a certain online auction site. Advertised as being "collector quality", outside it was in decent shape but inside it was a trashed wiring rat's nest. Some hack had miswired or disconnected the connections to the internal fuses, the external power connector and the batteries, and had completely destroyed the delicate analog meter movement. No wonder the seller made sure to say he had "forgotten" to take any pictures of the inside of the unit.
The meter itself is from the mid 1970's and is kind of a digitized version of the venerable Simpson 260. I like that it is auto polarity, and for resistance measurements has a low power 200 ohm range and also a 20 Megohm range. The small analog meter would have been usefull to check for capacitor leakage or peak up alignments, things a digital readout fails miserably at.
The meter itself is from the mid 1970's and is kind of a digitized version of the venerable Simpson 260. I like that it is auto polarity, and for resistance measurements has a low power 200 ohm range and also a 20 Megohm range. The small analog meter would have been usefull to check for capacitor leakage or peak up alignments, things a digital readout fails miserably at.
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The 360 uses 4 NiCd C-cells for power, plus a wall wart charger. It can also run off 4 Alkaline C-cells, but the wall wart must be disconnected so it doesn't attempt to charge them. I salvaged 4 C-cell NiCd batteries for the meter from the old Tektronix 326 oscilloscope battery pack I replaced.
The case is in pretty good shape other than some scratches on the trim of both knobs. |
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Internally the batteries clips were ruined from leaky batteries, and the wiring to the battery compartment was a total mess. New battery contacts were made from sheet brass to replace the contacts that couldn't be cleaned. I found a schematic online and sorted all the wiring to the batteries, charger connector and the two fuses for the low ohms and low current scales. Plus there were numerous wires broken off at the PCB from being flexed too much and several capacitors with broken leads or corrosion that needed replaced.
When first powered up the meter would zero but trying to measure anything caused it to go overrange. This was traced to an LM2901 quad comparator with three bad sections. It's in the upper left corner in the IC socket. I added the socket for convenience. |
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After finishing up with a good cleaning and a calibration it's all working except the small analog meter. That was totally destroyed internally and is unobtanium now days. I plan to replace it with an LED bargraph unless I can think up something better.
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Here's the parts I replaced which includes corroded capacitors, caps with broken leads, and the bad LM2901.
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In this photo the meter is connected to my signature tracer's meter output. It's measuring the breakdown voltage of a zener diode.
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Page Created 2/22/2020
Last Updated 2/29/2020
Last Updated 2/29/2020
