EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: stereo71 on March 11, 2014, 04:20:15 pm
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Hi,
Been working on a pair of 8062a meters, older ones with 1982 date codes. They have the usual leaking caps, corrosion on the MAC socket, etc. I replaced the socket and caps on meter #1, cleaned everything with IPA, it's working okay but need a calibration.
Now, on meter#2, which has the cleanest LCD and should be the best candidate for restoration, some previous work has been done, including a new Z5 resistor block (with 1997 date code) and maybe Q1. At least there has been previous solder work. Problem: VR3 zener has been removed, nothing in it's place. I don't really want to finish work without replacing it, although I won't be using the external 12v power jack when done...and I can't find a 1N963b device to put in there. I can get a 1N5242b, would that work? And, is it even necessary, as it seems it's main function is to regulate the voltage from the jack in case the input is over 12v? Maybe I'm wrong here...what do you think?
Thanks!
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Hi,
Problem: VR3 zener has been removed, nothing in it's place. I don't really want to finish work without replacing it, although I won't be using the external 12v power jack when done...and I can't find a 1N963b device to put in there. I can get a 1N5242b, would that work?
Thanks!
If you are in the US, you can get the 1N963b from an e-bay seller. This is what I did when I had the same problem.
Based on my limited electronics experience, I'd advise not to leave it out entirely, just in case someone ever plugs something into the power jack. I believe you can use the 1N5242b. However, I'd wait for our meter repair experts to advise you before doing so, in case I'm incorrect.
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Pretty much the same device electrically speaking. Should work as a drop in replacement as overvoltage protection.
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Thanks guys...I'll hunt down the correct part, that would be best. I'm getting a bit impatient wanting to test it with new caps, and don't know if it worked with that zener absent before. I'm thinking it did, as long as the 12v jack wasn't used. Before I started the cap replacement/cleaning, it would boot and self-test okay, but I didn't want to run it with those leaking caps in place. Probably should pull the MAC and check the socket, could be nasty like the other one was. Replacing that was tedious work! Many thanks to Mr. ModemHead for posting the 8060a info in his MAC adventure! That's what started me on this particular quest. Onward!
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. . . and don't know if it worked with that zener absent before. I'm thinking it did, as long as the 12v jack wasn't used.
I know for a fact that they will work fine without it. Also, the switch in the external power jack interrupts the battery when the power jack is used, and the contacts can get damaged so that battery power won't work.
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Okay, thanks...I'll get on the bay and find that zener, just to be correct. Hoping out of the two 8062a units I'll get one good one working! If they don't both survive, I'll have spare parts in the bin. Some of the switch buttons are broken on one unit, LCD is a bit shadowy on the first one, but is has good contrast and all segments work. Nice testers if I can get them up and stable.
Anyone know a good source to calibrate one of these?
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Some of the switch buttons are broken on one unit,
Modemhead is on the road for a while, but he has fixed up some buttons with photo documentation. I'm sure once he has more time, he will make a blog entry.
Anyone know a good source to calibrate one of these?
I buy used/abused meters and while fixing my own 8060A, I washed it twice in IPA, scrubbed the pcb and components vigorously, took no ESD precautions, lifted one solder pad and used cheap used no name caps.
With all that mind, it was still "spot on" with other meters I have at home so I would be surprised if either one of your 8062A required calibration.
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I'll finish and then compare. I was careful not to disturb the adjustment pots, but I always assume that during the "restoration" process and parts replacement, tolerances are changed, and that has some impact on overall performance of the unit. Maybe this comes from experience with too many audio amplifier overhauls!
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The only problem I had was with ACV. It was well out of specification. I later discovered that one of the caps that leaked spewed its electrolyte onto the ACV calibration pot. I had to turn the pot all the way back and forth about 3 times to get it working. Since I rarely measure ACV, I did the best I could "calibrating" it.
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Many thanks to Mr. ModemHead for posting the 8060a info in his MAC adventure!
BTW, the lead designer of the 8060A, Dave Taylor, posted some great information regarding the 8060A at
https://www.eevblog.com/forum/testgear/old-fluke-multimeters/ (https://www.eevblog.com/forum/testgear/old-fluke-multimeters/)
He was also on the amphour.
The 8062A is basically a slightly cost reduced version of the 8060A.