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| Old Fluke Multimeters |
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| ogdento:
Very true Smmi! Turns out that blob of blue/green on the chip is actually paint - Modemhead's got a ceramic chip in one of his 8060 repair entries with a similar blob. And I think the power input jack is actually OK, the plastic is a little rough but I think flash did it a grievous injustice ;) I really like the 87s too... I forget that they're 30 years old! Great meters, easy to work on, and I love that the service manual is so inclusive. |
| Dave Wise:
As I said in post #650 of February 13, 2019, I have an 8100B that read slightly high. I was able to bring it spot-on with a slight tweak to R175 ZERO. I'm still curious about the other ADC adjustments (R308 TRIP POINT, R149 REMAINDER), but it's pretty useful as is. I don't see a separate thread for differential voltmeters, so I'll say here that I just got a tube-type 825A/AG back on its feet. This model is a premium version of the 801B with a 1mV null detector vs 10mV. The /AG means the reference is a Zener instead of a standard cell. Unusual cap failures: a leaky electrolytic that depressed a regulator, another leaky electro coupling cap causing null detector offset, and an electro that was pretending to be a battery. I rarely see a leaky low-voltage electrolytic that causes a malfunction, usually they just dry out. Unusual cap, that failed: Why did Fluke use a paper/oil bumblebee? In a sensitive spot in the regulator? While the rest of the film caps are mylar? Also a rectifier with photodiode action causing more-than-full-scale offset on the recorder output. When I accidentally applied high voltage on a low range, one of the polystyrene input filter caps gave its life to protect the neon that was supposed to protect it. But after one hour in total darkness, the neon fired at 92V so it just must have been the cap's time to go. Not having a 0.1uF polystyrene, I used polypropylene. The plastic number wheels were warped causing them to rub one another making the action rough. This probably afflicts the 801B and other models that use them. I fabricated good-looking replacements using the original metal hub, a cut-down CD blank, legend overlay designed in LibreOffice Draw, and self-stick plastic laminating sheet. They look great, and the knobs slip from one detent to the next with that smooth ringing clank like they're supposed to. I'll post the recipe if anyone wants. The switch contacts were dirty, but they quieted after a shot of polyphenyl ether. I was beginning to compare it to my gold standard 895A when the latter failed. Not my favorite scenario. But it turned out to be simple, just an open electrolytic in the 1100V Reference Supply, parts are on order. Four Nichicon UCA-6 (short and wide) 22/450. It's been a good week. Dave Wise |
| JdaleH:
As some of you may have read, I have three 8060A multimeters. All seem to work, but have bad displays. I have opened the worst one up to gain some experience with it. All the displays have blurred numbers and black areas, so I don't know if I can resurrect them. Hopefully, one or more working displays might show up from members here. Just in case, I am looking at the prospect of converting one or more displays to discreet 7-segment displays with individual LEDs for the various other function indicators on the display. I got a schematic from manualslib that shows the pinout between the microprocessor and the display (see attachment). I can follow most of the pinouts except for the ones that go to other functions where two functions are apparently toggled by a single pin....look at BT and minus (-) for example. I can't figure out how to accomplish that. I hope someone can help me with this. I am pretty good at doing pcb layouts if I understand the circuit, but I'm no EE. Hopefully, Dr. Taylor can shed some light on this. Regards, Dale KS4NS |
| george.b:
--- Quote from: JdaleH on January 02, 2020, 03:28:05 am ---Just in case, I am looking at the prospect of converting one or more displays to discreet 7-segment displays with individual LEDs for the various other function indicators on the display. I got a schematic from manualslib that shows the pinout between the microprocessor and the display (see attachment). I can follow most of the pinouts except for the ones that go to other functions where two functions are apparently toggled by a single pin....look at BT and minus (-) for example. I can't figure out how to accomplish that. I hope someone can help me with this. I am pretty good at doing pcb layouts if I understand the circuit, but I'm no EE. Hopefully, Dr. Taylor can shed some light on this. Regards, Dale KS4NS --- End quote --- If it helps, that has been done before. See http://mrmodemhead.com/blog/a-very-unique-fluke-8060a/ ModemHead is in this forum and has participated in this very topic regarding this very theme. He might be able to help you. |
| JdaleH:
It looks like Dimitri had the same issue. He only brought out the minus (-), KHz, and diode functions to the display. If that's all that can be done, I can do that. Dale |
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