Anyone have a calibration routine for a Craftsman 982408 / 82408 multimeter (or similar)? I can't seem to discover the MFG. It has 3 calibration points, so far as I can tell. A blue-colored VR1 near the LCD, then a VR2 and 3 elsewhere on the board. I've had this thing since the early 1990s, or maybe even late 80s (as best I can recall). Normally, I would not bother with calibration on a thing of this type, but it thinks I have 147v on the mains!! Its battery reads 9v; appears good. Thanks!
Calibration Routine for Craftsman Multimeter
- Thread starter mbruffey
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Rabid Badger
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- Apr 2, 2018
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Nice work!
rancherbill
Well-known member
Caps die. Glad you found it.
Looks good. Properly calibrating the meter is likely going to cost more in service fees or equipment than the meter is worth. I have seen people selling a test board that has a precision voltage source and precision resistors plus the tested values of those items. I think some of the multimeter review guys on Youtube were using them. Testing against a known good meter is OK. However, if changing the caps seems to have put the meter back in spec, so much the better. It's possible those parts aren't part of the precision measurement chain in the meter. Given they were electrolytics, it's quite likely.
bwringer
Well-known member
Nicely done! It took me a minute to work out what you did there.
My office is located in one of the oldest parts of the city, and the power at our outlets tends to be very dirty and highly variable. We keep all our computer equipment on better UPS units mainly to filter the outages, noise, blinks, sags, brownouts, and surges, and keep the voltage steady. We get about four years out of most UPS units.
Anyway, the first time I "sanity checked" a meter with an outlet before using it for something else, I thought I was going crazy. I've seen anywhere from 109VAC to 129VAC at our outlets. It's slowly gotten a little better as the power company has updated and replaced ancient infrastructure. On the plus side, we have fiber internet to our building, so that's been mighty nice...
My office is located in one of the oldest parts of the city, and the power at our outlets tends to be very dirty and highly variable. We keep all our computer equipment on better UPS units mainly to filter the outages, noise, blinks, sags, brownouts, and surges, and keep the voltage steady. We get about four years out of most UPS units.
Anyway, the first time I "sanity checked" a meter with an outlet before using it for something else, I thought I was going crazy. I've seen anywhere from 109VAC to 129VAC at our outlets. It's slowly gotten a little better as the power company has updated and replaced ancient infrastructure. On the plus side, we have fiber internet to our building, so that's been mighty nice...
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dnschmidt
Well-known member
Capacitors are the most common failure points. Probably the least robust of all electronic components including semiconductors. Always wise to check the caps. Luckily they often signal, as yours did, that they're bad by leaking. Sure makes troubleshooting easier.
like2wheel
Well-known member
Any advice to a total novice on how to diagnose and test a cap?
Can it be done while still on the board?
Can it be done while still on the board?
@like2wheel: I used this for the electrolytics: https://www.ebay.com/itm/221171691277. I think I took 'em out. If circuit is open, can test in circuit. Discharge caps first.