Fluke 115 Wont Turn On - Page 1
Forum section: electronics / repair

author: shmadul
author_rank: Newbie
timestamp: March 27, 2018, 01:17:21 pm
content: I have A Fluke 115 Multimeter which I picked up a few years back at a garage sale for $5, Recently the 9v battery in it died, and rather than going out and buying one, I decided to just rig up a lipo battery from a battery bank to the terminals.....(I know.... I know, I wasn't using my head)Now it wont turn on at all, even with a good 9v battery,I assume there is just a fuse somewhere that I blew, Im just not sure where, and without my beloved continuity mode I need some help

author: PedroDaGr8
author_rank: Super Contributor
timestamp: March 27, 2018, 02:36:58 pm
content: Quote from: shmadul on March 27, 2018, 01:17:21 pmI do not believe there is a fuse between the battery and the control IC. Likely you damaged one of the voltage regulators. If you are lucky only that and not the control IC. If you damaged the control IC then the meter is toast.Sent from my LG-LS998 using Tapatalk

author: shmadul
author_rank: Newbie
timestamp: March 27, 2018, 03:26:59 pm
content: The odd part was that It turned on with the lipo battery connected, but displayed the low battery screen, but after I restarted it, It wouldn't come back on

author: PedroDaGr8
author_rank: Super Contributor
timestamp: March 27, 2018, 03:38:23 pm
content: While that is a bit strange, there are a variety of things that could have still killed it.First thing I would do is install a fresh 9V battery and check the voltage between the terminals. If it is 9V then nothing is shorted but something is still damaged, if it is much lower than 9V then something is shorted to ground (and repairing that will likely fix it). If it is being pulled to ground, let it run a minute and then find the really hot component and replace it. Otherwise, start following the voltage to the Vreg and see if it is doing its job. If not, then its possible a LOT was damaged but try repairing it. From there just keep following the voltages until you reach the IC. If everything looks good going into the IC, sorry the meter is toast.

author: shmadul
author_rank: Newbie
timestamp: March 27, 2018, 03:42:06 pm
content: Well At least I have the Multi meter on my Scope, Ill give it a shot, Thanks

author: PedroDaGr8
author_rank: Super Contributor
timestamp: March 27, 2018, 03:44:46 pm
content: Quote from: shmadul on March 27, 2018, 03:42:06 pmLooking at the circuit board a bit more, the FIRST thing I would check is CR1, which is the reverse voltage protection diode between the two battery pins. If this is damaged, you will have a direct short between the pins and NOTHING will work.Also, I can't seem to find the part number for U3 but I have a feeling that is the main Vreg. If you can provide the part number for U3 then I can let you know which is the output pin.Lastly, there are a metric boatload of tantalum caps in these meters. These things love to go bad, it would not surprise me to see one of them damaged. So yeah, a lot of areas for possible failure.

author: shmadul
author_rank: Newbie
timestamp: March 27, 2018, 07:02:17 pm
content: Thank You, I will check as soon as I get home

author: shmadul
author_rank: Newbie
timestamp: March 27, 2018, 11:18:02 pm
content: I get home, I test all said points, everything seems to be doing its job, out of frustration, I throw it back together and slap the back on (Same battery I las† tested i† with) and i† fired right up !! I've learned my lesson, just buy the dang batteries