Fluke 8840A/AF Repair - Page 1
Forum section: electronics / repair

author: br4n_d0n
author_rank: Contributor
timestamp: May 11, 2023, 09:29:00 pm
content: I'm in the process of trying to diagnose my meter and cannot determine if the VFD died or if the unit is even properly powering on anymore.My current issue though, is that I'm unable to get those stupid f***ing plastic rivets out of the optional RMS board for the life of me. I've tried pushing up on the center from the bottom (usually how these things work), pinching the prongs together, trying to pry it up from the top side, and even tried to remove the rivet holder from the side of the case, but that resulted in me breaking one of the tabs off (top right in picture).At this point I don't care if I destroy these plastic rivets so long as I don't ruin anything on the board and I can get it out so I can take a look at the VFD.Any suggestions?

author: bdunham7
author_rank: Super Contributor
timestamp: May 11, 2023, 09:46:26 pm
content: I use a bent-nose pliers, a large flat-blade screwdriver and a lot of care and patience. You want to push up on the pin while putting exactly the same counterforce on the lower body. Sometimes you still might break one. There's no magic trick that I'm aware of. Don't break anything else in the process. Your local auto parts store may have replacements that will work well enough.As far as troubleshooting, do you hear a 'click' about 3 seconds after you turn it on? If so, and no display, you probably do have a bad VFD.

author: br4n_d0n
author_rank: Contributor
timestamp: May 11, 2023, 11:11:18 pm
content: Quote from: bdunham7 on May 11, 2023, 09:46:26 pmI'll probably replace them with something less prone to getting stuckQuote from: bdunham7 on May 11, 2023, 09:46:26 pmThis sounds about right, but I'll have to confirm tomorrow.

author: lowimpedance
author_rank: Super Contributor
timestamp: May 12, 2023, 12:21:26 am
content: If you do still have a broken VFD, and have ruled out dry joints or lack of filament power/ cracked glass etc. Then see this thread, if not already ! ...;https://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/

author: TheDefpom
author_rank: Frequent Contributor
timestamp: May 12, 2023, 12:57:24 am
content: Just break the rivets off and replace them, you can buy new ones on Aliexpress for instance, I picked up a bunch of them when working on the Datron multimeters as they use the same rivets and they also tend to get stuck or break off.

author: br4n_d0n
author_rank: Contributor
timestamp: May 12, 2023, 02:32:02 am
content: Quote from: TheDefpom on May 12, 2023, 12:57:24 amI've tried breaking them off with the tools I had, but they refused to come out. That's why I'm asking for suggestions. The only other thing I could look at is see if I could borrow some tin snips and try to snip the underside portion, but this sounds like a disaster waiting to happen.

author: bdunham7
author_rank: Super Contributor
timestamp: May 12, 2023, 02:48:15 am
content: If you get desperate you can warm them up with hot air (if you have a hot air gun with a small nozzle--don't go baking your meter with a paint stripper!) or carefully drill them out. FWIW, I've worked on dozens of these and always managed to pry them out without breaking much other than the rivets themselves. I have actually slightly injured myself once in the process, though.

author: br4n_d0n
author_rank: Contributor
timestamp: May 12, 2023, 02:58:17 am
content: Side question: What's the difference between the 2.3 firmware and newer versions?

author: bdunham7
author_rank: Super Contributor
timestamp: May 12, 2023, 03:12:23 am
content: Quote from: br4n_d0n on May 12, 2023, 02:58:17 amI don't know of any operational differences between ROM versions and AFAIK the versions just deal with different hardware, mainly (and perhaps only) the different versions of Z8 processors used over the years. What is the history on your unit? Did you get it broken or did it work for you and then quit? There's a V2.5 for the 8840A/AF, haven't seen V2.3.https://www.hollywoodcontrols.com/phpFluke/HC8840AF_roms.php

author: br4n_d0n
author_rank: Contributor
timestamp: May 12, 2023, 04:38:09 am
content: Quote from: bdunham7 on May 12, 2023, 03:12:23 amI purchased this meter in a slightly beat up shape with the hopes of getting it working because normal equipment is too expensive for me :'( heck this was quite pricey as it was. Because of this, I'm unable to determine the age of the device unless there is a way by referencing the serial number or something else. As for the firmware version, this AF model has a chip with a sticker on it that reads v2.3.

author: alm
author_rank: Super Contributor
timestamp: May 12, 2023, 08:25:57 am
content: Quote from: br4n_d0n on May 12, 2023, 04:38:09 amMany ICs and some transistors will have a four digit date code printed on them. The format is YYWW, so 9325 refers to week 25 of 1993. Look around the board for date codes. The newest date code you can find is likely close to the manufacturing date of that board unless it was repaired or upgraded (firmware).For the rivets what worked for me was hold the base and pull on the top. As soon as all are popped out, you can remove the board. You don't have to remove the rivets from the RMS board.

author: br4n_d0n
author_rank: Contributor
timestamp: May 12, 2023, 08:42:00 am
content: Quote from: alm on May 12, 2023, 08:25:57 amHuh?

author: J-R
author_rank: Super Contributor
timestamp: May 12, 2023, 08:51:13 am
content: I echo alm's suggestion. I have three of these that I've repaired, and the "trick" is to ensure the outer portion (base) is being firmly pressed down while you wiggle and pull up on the inner pin. You don't remove the pin completely, just pop it up enough to loosen the base. You also don't remove the base from the board, you simply pull the board up with the bases and pins all still attached.

author: J-R
author_rank: Super Contributor
timestamp: May 12, 2023, 08:54:42 am
content: Forgot to mention, one of the top culprits for the display not working correctly would be the transformer connection to the PCB. Hit all the transformer pins with a soldering iron and that may fix your issue.

author: J-R
author_rank: Super Contributor
timestamp: May 31, 2023, 10:20:54 pm
content: So did you ever get this repaired?

author: br4n_d0n
author_rank: Contributor
timestamp: June 01, 2023, 01:04:47 am
content: I haven't had the time, I've been busy with other thing, but I plan on getting to it at some point. I will have to make some plastic parts on my 3D printer because Fluke finally got back to me and have no parts or alternatives they can suggest, which I figured with such an old device.

author: Kjo
author_rank: Regular Contributor
timestamp: June 20, 2023, 11:40:27 pm
content: I have new rivet & plunger sets available on both my website and on eBay.If you break the rivets, it is important to replace the main PCB ones if not the adapter boards.Even new rivets are delicate and require a specific insertion sequence if you are not to break them!I also have display modules pre-wired and complete display assemblies available using AHOL blue LEDs.The new display assembly uses ENIG gold for reliable operation with the old Fluke carbon pushbuttons.Start here for eBay:https://www.ebay.com/str/hollywoodcontrols/Suplus-Equipment/_i.html?store_cat=985206012Or here for my web store:https://www.hollywoodcontrols.com/phpFluke/HC700013P.phpkjo