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Of late, I've been having one of my two Fluke 8060A DMM's not turn on. Not yet willing to admit defeat, I kept cycling the green power switch on/off until it began showing signs of coming to life (fresh battery). Sometimes this would take up to a minute. Pressing on the upper end of the body, pressing down around the upper end of the LCD display, other places to see if it's some contact issue inside, then it wakes up, all ok. For a while. It would also sometimes lock up and not update the reading. Another oddity I first began noticing was when reading high DC voltages (plate voltage, plate supply voltages, it would sometimes beep at me, then lock up and go thru not wanting to read until I turned it on and off a few times to restore order.
So, today, I removed the battery, then the three #6 thread-forming screws that holds the top cover in place, then remove the screw thru the calibration shield, so I could then lift that off and slip the meter out of the bottom cover. With it out I brushed out the dust & debris that had gathered under the switch buttons on the PCB. Removed the GRN power switch actuator lever over the small SPDT power switch. Brushed in a little bit of Caig DeOxit into that. Looked closely at all of the solder joints, though all looked fine (using my surgical headlight & loupes). Then, removed the two screws holding the LCD assembly to the main board. Underneath that is Fluke's main 40 pin LSI IC. I carefully pried it up from both sides, just enough to get it ready to come out, then pushed it back in, just to wipe the contacts. I brushed on some Caig DeOxit over the PCB contact pads that mate with the fine contact strip of the LCD assembly to the main PCB, then re-seated that assembly, screwed it back into place. Cleaned the glass surface of the LCD display. All else looked ok, so I put it back together in reverse order, after first cleaning off the dirt accumulation on the rubber contact button strip (Hz, dB, Beep, REL functions), and put it back into place. Drove the three screws back into place, put the battery back in, closed its' lid.
Now it powered up immediately first time. I haven't gone thru a full systems check, with a resistance decade box, DC source, AC source, then Hi Voltage to see if that beeping and lockup problem is still there. I've so far just checked it with my Audio Analyzer's oscillator, ranging it from 10hz-100kHz, -50dBV thru +20dBV, and all is tracking fine there. 0 thru +/- 20VDC have been fine. Diode test ok. I'll get to the rest shortly.
Feeling a bit more brave (I don't always pull these instruments apart...only when needed), I pulled the cover off my other one. Almost immediately, I wish I hadn't. The lower cover screw removed, the molded recessed screw-shoulder relief fell apart into seven pieces, and the mating screw thread boss of the top cover has two lengthy cracks in it, running a good half-inch down it's length. Sigh...........
I tried briefly to re-assemble the shrapnel of the recessed cover screw-shoulder thing, using super glue. That went nowhere fast, and I gave up on that. The thead-forming screw is 3/4" #6 PH....an odd looking screw if you've never seen one. The two different height pitches, one high, one low as the spiral up the shank. I thought if I were to glue the mating boss cylinder walls back together, I could buy a 1" long screw, pass it thru a nylon shoulder washer that now pulls down on the outside of the case, rather than inside, since there's no more recessed body to work with.
There was just enough space at the top of the mating screw boss to slip some lacing cord around the top of it, and tightened it up firmly. After trying to thread different thread-cutting screws into it, just to see what I had that was long enough, I backed away from that thought, as it was stressing the cracks in that part of the molded assy. I then cut a piece of cable jacket, long and thick enough to slip over it, as it is placed between two of the three molded insulator cylinders of the meter's connectors, and clamped it down with a machinist clamp. Then, I drove a #6-32 tap down it's throat, cutting those threads all the way down to it's depth, backed the tap out a couple times to expell the cut plastic debris. That was enough to drive a long #6-32 machine screw in, and wasn't distorting the body cracks.
I then repeated the maintenance on this DMM's innards, as I had done on the other, then put it back together, this time using a 1" long #6-32 PHMS, with a nylon shoulder washer under the screw head on that lower screw hole, tightened it up as much as I dare, and tried it out. Working fine again. Ran some initial comparison readings between the two meters, and see each are within a few LSD's in their readings. Close enough for rock n' roll.
I still have to see what these do with plate voltage levels, as that was a recent development that made me nervous....my other DMM's here can't read beyond 300VDC (the Philips PM2535) and beyond 250VDC (HP 3467A 4-Ch logging DMM). I do have an old Simpson 460 Series 5 which is battery powered and has the small analog meter in the lower left corner. I gotta repair the charging circuit for the D-size NiCd batteries on it, when I get a chance.
So, today, I removed the battery, then the three #6 thread-forming screws that holds the top cover in place, then remove the screw thru the calibration shield, so I could then lift that off and slip the meter out of the bottom cover. With it out I brushed out the dust & debris that had gathered under the switch buttons on the PCB. Removed the GRN power switch actuator lever over the small SPDT power switch. Brushed in a little bit of Caig DeOxit into that. Looked closely at all of the solder joints, though all looked fine (using my surgical headlight & loupes). Then, removed the two screws holding the LCD assembly to the main board. Underneath that is Fluke's main 40 pin LSI IC. I carefully pried it up from both sides, just enough to get it ready to come out, then pushed it back in, just to wipe the contacts. I brushed on some Caig DeOxit over the PCB contact pads that mate with the fine contact strip of the LCD assembly to the main PCB, then re-seated that assembly, screwed it back into place. Cleaned the glass surface of the LCD display. All else looked ok, so I put it back together in reverse order, after first cleaning off the dirt accumulation on the rubber contact button strip (Hz, dB, Beep, REL functions), and put it back into place. Drove the three screws back into place, put the battery back in, closed its' lid.
Now it powered up immediately first time. I haven't gone thru a full systems check, with a resistance decade box, DC source, AC source, then Hi Voltage to see if that beeping and lockup problem is still there. I've so far just checked it with my Audio Analyzer's oscillator, ranging it from 10hz-100kHz, -50dBV thru +20dBV, and all is tracking fine there. 0 thru +/- 20VDC have been fine. Diode test ok. I'll get to the rest shortly.
Feeling a bit more brave (I don't always pull these instruments apart...only when needed), I pulled the cover off my other one. Almost immediately, I wish I hadn't. The lower cover screw removed, the molded recessed screw-shoulder relief fell apart into seven pieces, and the mating screw thread boss of the top cover has two lengthy cracks in it, running a good half-inch down it's length. Sigh...........
I tried briefly to re-assemble the shrapnel of the recessed cover screw-shoulder thing, using super glue. That went nowhere fast, and I gave up on that. The thead-forming screw is 3/4" #6 PH....an odd looking screw if you've never seen one. The two different height pitches, one high, one low as the spiral up the shank. I thought if I were to glue the mating boss cylinder walls back together, I could buy a 1" long screw, pass it thru a nylon shoulder washer that now pulls down on the outside of the case, rather than inside, since there's no more recessed body to work with.
There was just enough space at the top of the mating screw boss to slip some lacing cord around the top of it, and tightened it up firmly. After trying to thread different thread-cutting screws into it, just to see what I had that was long enough, I backed away from that thought, as it was stressing the cracks in that part of the molded assy. I then cut a piece of cable jacket, long and thick enough to slip over it, as it is placed between two of the three molded insulator cylinders of the meter's connectors, and clamped it down with a machinist clamp. Then, I drove a #6-32 tap down it's throat, cutting those threads all the way down to it's depth, backed the tap out a couple times to expell the cut plastic debris. That was enough to drive a long #6-32 machine screw in, and wasn't distorting the body cracks.
I then repeated the maintenance on this DMM's innards, as I had done on the other, then put it back together, this time using a 1" long #6-32 PHMS, with a nylon shoulder washer under the screw head on that lower screw hole, tightened it up as much as I dare, and tried it out. Working fine again. Ran some initial comparison readings between the two meters, and see each are within a few LSD's in their readings. Close enough for rock n' roll.
I still have to see what these do with plate voltage levels, as that was a recent development that made me nervous....my other DMM's here can't read beyond 300VDC (the Philips PM2535) and beyond 250VDC (HP 3467A 4-Ch logging DMM). I do have an old Simpson 460 Series 5 which is battery powered and has the small analog meter in the lower left corner. I gotta repair the charging circuit for the D-size NiCd batteries on it, when I get a chance.
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