はじめに
This repair guide is for fixing the "Error 6" (corrupted memory) message in a fluke Hydra datalogger. These units were built with Dallas Semiconductor or ST Microsystems MK48T08B real time clock/sram/crystal/battery chip. The error is caused by the "10 year" Li-ion battery inside the chip going bad - after 10 years - and the MK48T08B is no longer manufactured. These DIP-28 package chips are actually just a realtime clock and SRAM lower chip with a crystal and battery bonded to the top of the lower chip with wires encapsulated in the epoxy bonding. There's actually a gap between the chip and piggyback bonded assembly you can slip a piece of paper between, the packages and electrical connections are only attached to each other at the opposite ends where there are two leads for the crystal and two leads for the battery, both of which are enclosed by and potted into the rectangular module above. It's a simple repair, but caution is required while cutting the epoxy and preserving the potted crystal and 4 wire leads. Tools required:
-Phillips screwdriver to remove 2 screws in back and 3 screws (2625A) or 4 screws (2620A) on bottom of unit (varies by unit)
-Dremel tool with ~1" thin cutting wheel
-Tile nippers (or perhaps diagonal cutters + vice grips and a delicate touch)
必要な工具と部品
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Front view of unit, error 6 on powerup "configuration corrupted" caused by a dead battery potted into a realtime clock 28 pin DIP part that is no longer available. But there's always a way. To open the unit, remove the two screws in back and 3 or 4 screws on bottom (depends on unit) and slide off the cover.
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The corrupted configuration means that on each powerup cycle, the channel setups, time and date, and other settings all have to be re-entered with each power cycle event.
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This is the main circuit assembly on the bottom of the unit, showing the RTC/SRAM/xtal/battery chip with the dead internal battery causing the error.
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Here, I've just cut a hole out of a newspaper and applied tape around the perimeter to catch plastic and metal bits, rather than unsoldering the 28 pin DIP from the board. The Dremel cutting wheel is running at lowest speed for minimum telegraphed vibration to the board and display.
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Very carefully use the dremel cutter (low speed) to cut slots about 1/8" from each chip module end to free the top module from the bottom, be careful not to cut into the SRAM/RTC chip below, or to cut the 4 wires (2 each end) from the lower chip - we need those!
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At this point, you'll have the top module removed, and there will be two short wires sticking up at each end that we'll need to use. Excess epoxy stuck to the short wires can be crushed and removed with the nippers or pliers.
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Now we need to extract the crystal from the potted unit we sawed off. Tile nippers and small nibbles work great for this, be sure not to crush the cylindrical crystal (potted on left side in pic), no worries about the battery (right side) which was already toast, which is what brought us here.
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Solder the extracted crystal on the right side two pins (this runs the real time clock in the chip below), and solder two pigtails onto the left side for battery holder (next step). (Top left=-3V, Bot left=+3V on coin cell holder). Crystal on right is not polarized.
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You can verify battery polarity by checking that the "Gnd -3V" pin on the photo is a few ohms to a GND test pin on the circuit board.
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Solder short (~1.5") pigtail wires onto the SMT 16mm coin cell socket (digikey BU1632-JJ-GCT-ND or equiv), then solder those leads onto the sticky-up chip leads you freed in the previous step, use superglue gel to glue down the socket and crystal
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Note polarity on socket: double check that socket "-" terminal you wired to the sticking up IC pin is also electrically connected to GND of circuit board.
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install battery (CR1620 for example). Verify it all works by setting the date/time, which is done by pressing "SHFT" then "INTVL" and using the up/down arrow buttons and left/right and ENTER for YYYY MMDD and HHMM. Turn instrument off for a bit then power on and check it remembered those settings and ERROR 6 no longer appears.
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Re-install any cables and circuit boards you removed, after testing and verification, slide the outer shell back (with 3 or 4 flat head screws depending on model) on and the rear bezel (2 screws)
Re-install any cables and circuit boards you removed, after testing and verification, slide the outer shell back (with 3 or 4 flat head screws depending on model) on and the rear bezel (2 screws)
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