No.107 - Fluke 8846A 6.5 digit Multimeter Repair - Part 1

[@BTom16]

I love these repair videos and yours are the best of the bunch. Due respect, however, for the volcano craters that TheSignalPath rebuilds into working circuit boards. That guy is next level on rolling new copper traces onto a charred stump.

[@gordonwedman3179]

I get a headache just thinking about trying to fix that with no schematic. You are a brave and talented man. Thanks for the video. Good luck with part two.

[@denzilrobert9055]

Can't wait for part 2 Ian. Keep up the good work fella.

[@radio-ged4626]

Enjoyed this video as it is much closer to the way I have to work. No circuit diagrams and another broken set for comparison that is a slightly different revision. It's good to see someone else working at my level as I am on my own in my job. The other guy in my workshop is learning from me. So I have no one else to improve myself with. It's a lot easier to improve your skills when your work partner is at the same or better level than yourself. That said, when someone is learning from you, they sometimes ask questions that make you think and try a different way around a problem. So I suppose it's all good. 😂

[@IanScottJohnston]

Actually that's a good point I haven't thought a lot about before but have certainly experienced. A bit like having a boss that is totally clueless and makes stupid requests and questions all the time. Aaarrrgghhh!

[@radio-ged4626]

@@IanScottJohnston 🤣🤣🤣

[@remcovantriest4357]

Love your videos. You get into it step by step. I copied your approach, I learned a lot looking at your videos. After seeing your repair on the BB3 I ordered one myself . Working great so far 👍🏻👍🏻 Next step is to get one of your voltage sources one day, look like a nice bit of kit.

[@IanScottJohnston]

Thanks for the comments. Yep, the step by step is intentional......bringing folks along for the experience.

[@Andrewausfa]

Good stuff Ian. Hard things to work on with no circuit information.

[@remdale801]

Great video, thank you! Waiting for part 2 because my 8846A is showing overload in each mode too

[@Scorpio722]

Looking forward to part 2. Great videos.

[@IanScottJohnston]

Me too!......alas could be a while as it's particularly hard without a schematic on this DMM.

[@Scorpio722]

@@IanScottJohnston yes, I can imagine. I've had similar issues with other devices when schematics are not available. Valiant effort.

[@fredflintstone1]

Nice video Ian, considering the date I was expecting you to find a dead haggis under the PCB as the fault 🙂

[@IanScottJohnston]

They are all in hibernation this time of year unfortunately.

[@tfinmoraes]

Hi Ian, you got a new subscriber here. Thank you for your efforts sharing all this. Quick follow up on the part 2, is it coming? I hope so! Best regards!

[@IanScottJohnston]

I haven't got back to look at the 8846A's yet, proving to be really hard to repair without schematics. They are still here though......

[@tfinmoraes]

@@IanScottJohnston Yes, I hear you. I have one myself to be repaired, and Fluke really did a job at preventing schematics from going public. I have considered reverse engineering it just for the sake of it, but didn't really took a time for that. Thing with Fluke's DMMs is that quite often the custom ASICs go bad, and that is really a bad deal - you can't really find it unless you have a donor. BTW, excellent work with the Keithley 7001! Mine's been showing a different error, maybe I'll make a video out of it too.

[@Zh4n6Wu]

Hi Ian, it's a real shame that Fluke doesn't provide the schematics. But as always it's exciting to look over your back when troubleshooting.

[@IanScottJohnston]

Yeah, I kinda knew what Fluke were going to say in reply before I emailed them........oh well!

[@simontay4851]

Bastards. This is why we need right to repair laws.

[@PeterCut62]

Awesome video as usual.

[@nikmilosevic1696]

I enjoyed this, but did you ever get back to the 8846A's, I cant find part2.

[@IanScottJohnston]

I’d love to get back to them also…….all I can say is this year LOL!

[@lohikarhu734]

Ian...you seem to be able to find and get parts for these meters, et al.... I have a meter that had its 10M input resistor zapped, and I can't seem to source a precision 10M smd resistor (that kind of big, 300 V package), precise enough for my 500,000 count multimeter (advertised as 50,000, but 500 k internally). Where would you go for such a thing? I thought about getting something like 9.x M and adding trim resistors to it, as I have a 6.5 digit meter, and a 1 M and 100 k .005% resistors to use as a test subjects.... Nice that I found your channel; watching repair of different devices gives some nice hints on sorting 'em out ... I have a 3314 A that needs a going through. Cheers! 🇨🇦🐻in 🇩🇪

[@IanScottJohnston]

I just shop at the usual places, RS, Farnell, Digikey, Mouser etc. Note that a large value precision resistor with a much less precision resistor in series with it as long as the 2nd resistor is many magnitudes smaller in value is a viable way forward.

[@jeditoto3441]

Great Video - I have a question about the power supply - what would be the typical temperature range for the regular heat sink? mine is at around 60 degree C - is this too high?

[@t1d100]

Excellent.

[@TheDefpom]

Not one but two !

[@IanScottJohnston]

I did hint at this......the workshop photo I posted on Twitter has both of them on the workbench....:-)

[@TheDefpom]

@@IanScottJohnston I didn’t notice the 2nd one.

[@andymouse]

Awesome stuff....cheers.

[@fredflintstone1]

Cheese!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[@andymouse]

@@fredflintstone1 Squeak !!!!!!!!!!!!!!

[@otherbasis8505]

The chain of transistors is a protection on ohms range (described in AOE3x page 353). Check if current being pushed through when in ohms.

[@farazahmed9247]

Can you upload part 2? it's been 2 weeks! please :p

[@IanScottJohnston]

LOL!, it's a tough repair this one.

[@jairamvishwakarma82]

Sir i have a resistance measurement issue in fluke 8845A model please help

[@otherbasis8505]

Weird power rails on first: most likely those are bootstrapped op-amps. I.e. their virtual ground is the input terminal.

[@pa1wbu]

Is it me, or did you have an unpopulated fuse holder? There appears to be one with a HRC (I assume) fuse. But the other one lacks a fuse it seems?

[@IanScottJohnston]

Thats the 400mA fuse for the mA range. I was swapping it between the two meters.

[@MrGabrovche]

The 60V is not there because it's only turned on when a digital signal is fed back to the unit from the VFD! So you will only have it with the VFD attached! I've done OLED upgrade for my unit and had to reverse engineer the whole VFD section...

[@amrahmed6471]

Part 2 please

[@hungtongle2691]

Sir!! I need part 2

[@amrahmed6471]

Sir you have part 2 please i need part 2

[@amrahmed6471]

Part 2 please 😢😢

[@TheEmbeddedHobbyist]

I hate over voltage faults, as you have no idea of what other chips on the board have been over stressed to the point of going feet up in a day or week or next month. I'd give it a good long burn in just in case. in the old days if that happened to a board in test or came back for repair it would be scrapped. but nice to see it avoiding the WEEE bin.

[@IanScottJohnston]

In the old days where I worked we had to repair just about everything.......gawd knows what it cost in parts over the years!

[@TheEmbeddedHobbyist]

@@IanScottJohnston We had to maintain tight controls on products, so you had to decide what the repair would do to the reliability. Or if it how it might impact the MTBF. so it was cheaper to scrap a board than to try and repair it for some faults.

[@SpeccyMan]

Nice multimeters but way out of the price range for a mere electronics hobbyist like me. Still, I can always dream of owning one. Fortunately the gear I do have is enough for my needs.

[@simontay4851]

The first multimeter. Where do you even start. Without the schematic, its going to be very frustrating and difficult. So many different SOT-23s. Thats why i like repairing old stuff. You can usually find the schematic, and you can easily read the part numbers.

[@IanScottJohnston]

Just gotta keep plugging at it......there's always a "ahhhhh, gotcha!" moment.

[@vaniz2012]

Part 2 please

[@IanScottJohnston]

I would love to publish a Part 2......but this repair is proving quite hard without schematics. It's on the back burner for now.

[@amirb715]

Did you give up on this meter?

[@IanScottJohnston]

No, still waiting to get back to it.

[@allthegearnoidea6752]

Oh pull off the cellophane I cannot take anymore

[@IanScottJohnston]

I can't, it's not my DMM.......aaarrrgghhh!

[@mikeiver]

To bad you are across the pond. I could loan you my perfectly working unit to test against. Shipping to and from would be rather expensive though.

[@IanScottJohnston]

I did have an offer of a local unit, but I'm not sure it would help much. I think a bit of reverse engineering will be necessary.

[@amrahmed6471]

Part 2 please 😢😢😢