Fluke 289 schematic or part identification help - Page 1
Forum section: electronics / repair

author: Sonicskater
author_rank: Newbie
timestamp: May 26, 2018, 06:55:06 pm
content: Does any one have a schematic for a Fluke 289 or willing to open theirs to let me know what a couple components are? I have a unit that the previous owner tried to open by prying the case and they took out C2 Q1 R1. The pads are still in place so I can solder on replacements. The meter works so not sure what part of the circuit this is for but they are located between the two middle meter lead sockets.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 26, 2018, 11:41:01 pm
content: there's no service manual available if i recall correctly, you have some thread here, maybe on some photos you can see a few parts, maybe they are for input protections since you say your meter seems to work ??

author: Sonicskater
author_rank: Newbie
timestamp: May 26, 2018, 11:58:30 pm
content: Thanks. I’ve zoomed in on any pictures I could find with no luck. It’s odd but the meter works fine, although I haven’t tried every feature but the common ones I would use all work.

author: retiredcaps
author_rank: Super Contributor
timestamp: May 27, 2018, 03:16:56 am
content: R1 looks like 104?, Q1 looks like 1AH?, don't know what C2 value is.See posthttps://www.eevblog.com/forum/reviews/fluke-287-dmm-teardown-and-photos/msg52680/#msg52680

author: ModemHead
author_rank: Frequent Contributor
timestamp: May 27, 2018, 03:03:07 pm
content: This meter uses optical detection for when plugs are inserted into the current jacks. The components in question are part the photo-transistor detector circuit for the mA jack directly on the other side of the board.Maybe the jack has some crud in it that causes the lead alarm to go off, and the previous owner removed the components to silence it. Just a guess, as I've done exactly this to a 27-II model with jacks that were damaged by solvent.The transistor "1AM" is a MMBT3904 general-purpose NPN transistor. The "104" resistor is 100K. I cannot get an in-circuit read on the cap, as I found a voltage differential on it due to the super-cap. Probably just a filter to prevent false triggering due to ambient IR?

author: Chris56000
author_rank: Frequent Contributor
timestamp: May 27, 2018, 04:28:12 pm
content: Hi!I use a 287 at work, but my manager'd be down on me like a ton of bricks if I took mine to bits without a good cause, but from examination of C2 in the piccy provided in the linked thread, I'd venture to suggest 100n 50V 0805 as a reasonable starting-point!Chris Williams

author: Sonicskater
author_rank: Newbie
timestamp: May 27, 2018, 06:18:55 pm
content: Thanks everyone for the help! Appreciate it.

author: retiredcaps
author_rank: Super Contributor
timestamp: May 28, 2018, 04:13:29 am
content: Quote from: Sonicskater on May 27, 2018, 06:18:55 pmLet us know if replacing these parts makes it work.

author: retiredcaps
author_rank: Super Contributor
timestamp: May 28, 2018, 04:14:25 am
content: Quote from: ModemHead on May 27, 2018, 03:03:07 pmI couldn't quite make out the last letter.

author: Sonicskater
author_rank: Newbie
timestamp: May 28, 2018, 04:56:46 pm
content: Quote from: retiredcaps on May 28, 2018, 04:13:29 amWill do, I had to order the parts but hope to have them by the end of the week.

author: Sonicskater
author_rank: Newbie
timestamp: June 10, 2018, 07:11:04 pm
content: Parts took longer to get here so I just now got it put back together. I found the capacitor in the case and it measures at 500nf. With the other parts now installed it works perfectly. Thanks again for all the help!