Fluke 8440A Quick Repair

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LazyElectrons

3 жыл бұрын

Quick Repair of two 8840A fluke Bench meters.
More info/Update/Bugs at
lazyelectrons.wordpress.com/2...

Пікірлер: 30

@keithnoneya 3 жыл бұрын

Thanks for the fun. I have one of these in my home lab, and also use several of the versions at work. They are pretty good meters with two exceptions. I don't like the Hysteresis and drift issues on the DC reading, specifically the Auto setting. - The Hysteresis problem with these meters is when you remove the leads they tend to keep the value up on the screen leading the technician to believe the voltage is still there/active.This can be a problem if the following reading has an open in the circuit, say in a rotary switch scenario. "IF" the reading is not what is to be expected I overcome this problem by shorting the two leads together then take another reading . I have had this Hysteresis problem on ALL the 8840A & 8840A/AF at work and at home. - The other thing I don't like about them is the drift issue with no input in the lower DC setting or DC Auto setting. It drifts up or down and never reads zero or close to it with no input into the meter or with the leads just sitting on the bench top. Those the only things I don't like about the meters. They are are very accurate and reliable if you can get past those two quirks in it's operation. Thanks for sharing. Best Wishes & Blessings. Keith Noneya

@LazyElectrons 3 жыл бұрын

Thanks Keith, thanks for sharing the details. I totally agree, I hate the Hysteresis problem in these that I dont use my 8842 at all for any troubleshooting things. Twice the pain and confusion.

@ricardonunes6724 2 жыл бұрын

I didn't watch the video yet, but I guess what you call hysteresis is probably just due to the very high input impedance of the multimeter. Probably in the lower voltage ranges, the multimeter has input impedance in the GOhms range. Whatever voltage was applied before, it will take a long time to for the capacitors to get discharged. The drifting voltage when the leads are not connected anywhere is probably also coming from the input impedance. The input impedance is so high that any leakage currents or charge makes the voltage drift. You can avoid this by simply changing the settings to use a lower input impedance.

@keithnoneya 2 жыл бұрын

@@ricardonunes6724 That's probably true for the cause but if you need the lower scales it can be a real pain in the but if you get distracted and forget to short the leads. Sometimes when I'm in a hurry and my accuracy has a wider window, I'll drop a 10 Mega Ohm resistor across the terminals and that solves the drift issue. So with a wider tolerance coupled with the specification offset being so wide it doesn't effect the alignment or reading of the equipment I use it on. Thanks for sharing. Best Wishes & Blessings. Keith Noneya

@FraidyZone 3 жыл бұрын

It's as good as new now! Brilliant as always!👌🏽😸

@LazyElectrons 3 жыл бұрын

Thank you! 😄

@brianwong4175 3 жыл бұрын

Nice job on the repair. When I saw that 470uF cap so close to the heatsink I suspected that it was bad. I have had to replace caps that were close to heatsinks in several pieces of my equipment as well. Definitely a design defect.

@LazyElectrons 3 жыл бұрын

Thank you. I was not expecting something silly like this in a Fluke.

@BTom16 2 жыл бұрын

Nice video. Thank you.

@fichambawelby2632 9 ай бұрын

Thanks for the video. Take care with the 2nd unit cap (the one with more capacity). This is a sign the cap has a high parallel resistance. The meter you are using won't tell you so. Replace all three.

@LazyElectrons 9 ай бұрын

Thanks for the info!

@fichambawelby2632 9 ай бұрын

@@LazyElectrons my pleasure! Anyway, I wrote before I saw, because you changed the three, hahahaaa! Thanks for sharing your knowledge. The video about the repair of the HP generator (>1 hour) is simply great!

@LazyElectrons 9 ай бұрын

Thank you! @@fichambawelby2632

@netautorisationnetautorisa545 3 жыл бұрын

*GREAT ... (JUST SEEN 1 LITTLE THING) I WILL USE THE REST OF MY LIFE ....* *THANK YOU ... MISTER*

@alexandrezanol Жыл бұрын

your blog article was great reading, thanks. Just picked up a 8842A as-is and I'm hoping it's ok or fixable

@gregorymccoy6797 2 жыл бұрын

Well done, Sir

@phuang3 7 ай бұрын

510uf reading of a 470uf cap is usually the sign of bad capacitor. The caps from Japanese brand are mostly less than their specified value where as the caps from Europe or US are sometimes larger.

@mymessylab 3 жыл бұрын

Nice job 👍. I wish to find some of them for my lab too🤞.

@LazyElectrons 3 жыл бұрын

you never know, can happen!

@GeoffEspeland 2 жыл бұрын

Can you use the 09 AC option out of a 8840A in an 8842A? Thanks

@GeoffEspeland 3 жыл бұрын

I have a 8840A and in DC mode the display is blinking at a rate of about one second per cycle. All voltages seem good. I don't know what setting to use on the scope to measure the ripple but I can't see any ripple problems. It has options 5 and 9. AC (rms) measurements work fine but no DC or resistance functions. self test results - 1-4 and 10.14 test good. 5-9 and 15-21 show error. At one point while turning the unit off and on for test, it worked properly but I never got it to repeat. I went ahead and replaced all 5 caps in this area anyway but to no avail. A - Any suggestions are greatly appreciated. B - What GRD point did you use for your meter and scope measurements? C - Are you in the USA and if you are do you accept units for repair? Thanks Geoff

@LazyElectrons 3 жыл бұрын

A) Manual p 6-25 lists some procedures to identify bulk errors, you can try that B) Ground pad (any) on the PCB. C) yes, I am in CA. contact info in about page. For measuring ripple, use AC coupling for the scope and dial the volt/div down after connecting the probe.

@roisoleilxiv14 3 жыл бұрын

I have a 8842A, where the display sometimes wont turn on. I have checked the voltage reference points and they seem to be good. There are no burn marks on any of the pcbs. Do you have a tip, what I can do to resolve this issue?

@LazyElectrons 3 жыл бұрын

Hey Roi, check if the meter is booting when the display is dead to confirm it is just the display, not the entire meter. If it is just the display it could be the interconnecting cable or bad components/cold joints on the display section/driver chip/power supply lines for the VFD. All the best.

@helmetdump 6 ай бұрын

Resolder the power transformer pins. especially pins #'s 14, 15 & 16 for the display voltage. Use plumbing flux when soldering. I resolved this blank display problem on several of these this way.

@roisoleilxiv14 6 ай бұрын

@@helmetdump I'll check that out! Thank you very much! Are there any signs on the solder points, that there is a fault?

@roisoleilxiv14 6 ай бұрын

@@LazyElectrons Sorry for my late response, i have somehow not seen your reply. The meter is definetly on, as the display sometimes is dimmer and/or gets off and back on. Thak you very much for helping me!