EEVblog Electronics Community Forum
Electronics => Metrology => Topic started by: View[+]Finder on November 25, 2024, 01:52:30 pm
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A Datron 1062 came my way by eBay . . .. {The start of every adventure} In my case this one was part of a purchase of Pomona parts from a seller in the Seattle area, and for a good price. Sadly, the battery was flat and therefore the CAL magic was lost. After replacing the battery and the "usual suspects" elec caps, I began the process of coaxing the meter back to working condition as it had a very good display and was free from any visible damage or "prior work". About two weeks of RTFM and de-oxit, the meter would read volts and amps albeit at the wrong values. So it was time for calibration.
Following the script exactly {EXACTLY, means look for decimal point in Ib and voltage setting in Lin}
Finally got CAL light ON and self-test to PASS BUT on SAVE 10VDC, the meter failed in what can best be described as a "light-show". No sparks or smoke, just every button on the front flashing randomly.
Just FYI, I herd the sound of a relay just as the CAL light came on. Now the relays were buzzing with the lights.
NO more reading voltage or anything. Just flicker on the display.
Any clue what happened? Is this the dreaded opto-coupler issue?
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I’ve done several videos repairing these units, my experience is that:
- All electrolytic caps have to be replaced.
- The plastic bolts holding the +/-15V regulators to the heat sinks degrade and break, so the regulators over heat and cause the 15V rails to turn off and on when they get too hot.
- The two round bridge rectifiers often fail and need to be replaced.
- ICs need to be reseated in the sockets to freshen up the connections.
- Tantalum caps like to randomly blow and short out the 15v rails (always replace with 35v, not 25v)
- The wires on the 5V regulator can be badly corroded by the flux that was used at manufacture, check it isn’t just about to fall off.
Check voltage rails, more than once, the last unit I did had tantalum caps blowing and keep on shorting the +/- 15V rails out.
You can narrow down faults by unplugging boards, it will run without the resistance, current, GPIB, AC boards plugged in, don’t forget the ribbon cables snd side rail connectors.
There are tantalum caps on the front panel between buttons, never seen those fail but there could always be a first time.
Some units have the front/rear input switching unit mounted in the back which has relays on it, that has tantalums too which I have seen fail.