Fluke 112 Service Manual or Schematic - Page 1
Forum section: electronics / repair

author: Kennylxix
author_rank: Regular Contributor
timestamp: January 30, 2017, 08:41:52 pm
content: Hi. I'm looking for a service manual or schematic for a fluke 112 dmm. I have searched high and low but no luck. Any help is greatly appreciated!Ken

author: retiredcaps
author_rank: Super Contributor
timestamp: January 30, 2017, 11:36:06 pm
content: Quote from: Kennylxix on January 30, 2017, 08:41:52 pmYou won't find any service manual with schematics/bill of materials for any modern or recent Fluke.If you have a problem with your 112, please state it and maybe we can help you fix it?

author: Kennylxix
author_rank: Regular Contributor
timestamp: January 31, 2017, 07:43:47 am
content: OKI bought the 112 as non working off eBay. Previous owner stated he just went to turn it on one day and nothing.I tried with a fresh battery as well as with my DC power supply and it is completely unresponsive . I looked over both sides of the board and found no obvious skid marks. I'm fairly new to electronics repair but have a basic understanding. I tried to trace the power going from the battery but it goes to an inner layer. Any help would be awesome.The leads I got with the meter pretty much cover what I paid for it but I definitely want to try to fix it

author: retiredcaps
author_rank: Super Contributor
timestamp: January 31, 2017, 09:11:30 pm
content: Quote from: Kennylxix on January 31, 2017, 07:43:47 amWhen hooked up to the DC power supply, what is the current draw?Please post clear focused pictures of both sides of the pcb.

author: Kennylxix
author_rank: Regular Contributor
timestamp: January 31, 2017, 09:43:28 pm
content: I was in a hurry during the initial test so I'm not sure how much current was being drawn. Ill have time tomorrow to find out abs take pictures.

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 01, 2017, 12:37:12 am
content: So at 9v its drawing around 2-3ma in all ranges.My camera decided to not work so pictures will be up as soon as possible.

author: retiredcaps
author_rank: Super Contributor
timestamp: February 01, 2017, 02:33:15 am
content: Quote from: Kennylxix on January 31, 2017, 07:43:47 amIs there anything on the lcd? Does it show 0.0 when rotary dial is set to DCV? If you measure a 1.5V AA cell, what does it show on the lcd?

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 01, 2017, 03:27:07 am
content: No it shows absolutely no sign of life no matter what I do. No display no beep nothing.

author: retiredcaps
author_rank: Super Contributor
timestamp: February 01, 2017, 03:54:10 am
content: Well, I'm sure others can help because I'm off for 9 days and won't be regularly visiting this forum starting now.

author: retiredcaps
author_rank: Super Contributor
timestamp: February 09, 2017, 05:21:08 am
content: Quote from: Kennylxix on February 01, 2017, 12:37:12 amDrawing 2 to 3mA doesn't sound abnormal.QuoteClear focused pictures would help.

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 09, 2017, 06:36:14 am
content: Ok here is a pic of the front and back. It looks like everything can be seen. I also had a poke around with my scope and didn't see any signs of data or clock but I didbt check ever pin. There are several voltages around the board which all seem steady though without a schematic I have no idea if they are right or nothttps://goo.gl/photos/VZRdAXYzSAJ12Sj47https://goo.gl/photos/ASyK33Q3eEfusdHt5I hope these help

author: retiredcaps
author_rank: Super Contributor
timestamp: February 09, 2017, 10:26:48 pm
content: The main asic in the Fluke 112 is the same as early generations of the Fluke 177. Seehttps://www.eevblog.com/forum/repair/multimeter-repair-time-again!-fluke-177-reads-8-ohms/?allI can't see the oscillator in your picture? Is there any signs of life there?

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 10, 2017, 01:52:27 am
content: I thing the oscillator is the silver thing just to the pictures left of the 10a fuse. I honestly didn't want to poke around too much without some guidance.Feel free to offer any instruction. It's already broken so we aren't going to hurt it:) I'm just not sure how to proceed. (I'm pretty green to this but I'm a quick study)

author: ModemHead
author_rank: Frequent Contributor
timestamp: February 10, 2017, 03:19:36 am
content: I don't have any direct experience with this model but I can throw out a few general things.Current draw is in the normal range, so nothing enlightening there.If the processor is alive, you'll find some slow (50 - 150 Hz) square waves or stair-step signals on all of the LCD lines. Doesn't sound like it's alive in this case.Examine the board carefully with light and magnification. Never know what you may find. Bad solder joints and spots of copper erosion are possible faults. Don't forget to examine the switch rotor and contacts too.Try to find data sheets for all of the little off-the-shelf chips on the board. The function of these chips may not be obvious, but at least you can find the power/gnd pins. You will probably find one or more voltage regulators, providing a place to check power rails. Use the COM jack as reference for analog ground. The analog measurement section usually has a bi-polar supply. The processor will probably have a +3.3V supply.

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 10, 2017, 03:37:40 am
content: Ok great info. I'll start identifying components and testing tomorrow. The switch and switch ring seem prefect but I haven't looked at anything under magnification yet. I'll post up what I find tomorrow.It'd be cool to fix this but I'm doing the repair attempt more for the experience than anything else.

author: retiredcaps
author_rank: Super Contributor
timestamp: February 10, 2017, 07:29:26 am
content: Datasheet for microprocessor is athttp://pdf1.alldatasheet.com/datasheet-pdf/view/249826/RENESAS/HD6433844.html

author: retiredcaps
author_rank: Super Contributor
timestamp: February 10, 2017, 07:32:35 am
content: Quote from: Kennylxix on February 10, 2017, 03:37:40 amThat is why I fix broken stuff. More for the experience and learning because some things aren't worth economic repair or obsolete.BTW, on modemhead's blog sitehttp://mrmodemhead.com/blog/all-posts/you will find a whole set of case studies. Some of them will have a corroded pcb where the solder or pcb trace is missing causing the meter not to function.

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 10, 2017, 08:10:04 am
content: Quote from: retiredcaps on February 10, 2017, 07:29:26 amI checked this link and it goes to a little development board. Am I missing something?Those case studies look awesome. Ima go check the out now:)

author: Muttley Snickers
author_rank: Unknown
timestamp: February 10, 2017, 08:36:22 am
content: These below are about all I have in the way of information for the 112 series, the data sheet for the H8/3844 is readily available on the net but too big to post here.

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 10, 2017, 03:04:26 pm
content: Thanks! I downloaded the data novel on the micro and hopefully can get some pinouts from that.

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 10, 2017, 09:31:47 pm
content: Ok I think this just turned into a salvage operation. I poked all over the board and whereas I found a bunch of different and stable voltages I found no signs of digital anything going on which leads me to believe the main processor is dead.So I think I'm going to pull a few components off such as the resistor network and fuse holder and junk the board. I'll hold onto the screen and case and wait till I can find an ugly one that works on ebay for not much money.

author: retiredcaps
author_rank: Super Contributor
timestamp: February 10, 2017, 10:29:00 pm
content: Personally I would save the entire meter for possible future parts. The spark gap, fusible resistor, PTC are difficult, if not impossible, to get on digikey/mouser because of their specialized values.

author: Kennylxix
author_rank: Regular Contributor
timestamp: February 11, 2017, 01:47:05 am
content: Hmm good idea. I was planning on pulling them but the board is small enough that I might as well store everything on it.