Fluke 91 Scopemeter - bricked? - Page 1
Forum section: electronics / repair

author: Leadfootin
author_rank: Contributor
timestamp: November 03, 2014, 06:54:38 pm
content: Battery died in my Fluke 91 scope meter. Unit would not boot when replaced and had to replace dead internal coin cell as well. Any ideas on how to revive this useful gadget?

author: obd.tech
author_rank: Regular Contributor
timestamp: November 04, 2014, 05:15:39 pm
content: I've had similar issues with battery operated kit.Have you tried different cycling patterns the coin and battery connections?.....sometimes works to reboot a 'knickers in a twist' confusion, things get into?Is the power getting to the pcb connections?Have you tried finding instructions or a reset on this kit?Hope this helps

author: Leadfootin
author_rank: Contributor
timestamp: November 04, 2014, 07:22:16 pm
content: Have tried all the usual tricks to get it going. Either a certain sequence is required for reboot or the cpu has completely lost it's memory. Still have not found instructions in this regard after quite extensive searching.

author: Leadfootin
author_rank: Contributor
timestamp: November 05, 2014, 08:10:33 pm
content: Anyone have a service manual? Section on changing internal battery should have the info I need.Thanks,Peter

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 05, 2014, 10:41:49 pm
content: Quote from: Leadfootin on November 04, 2014, 07:22:16 pmI'd look for that special reset button recessed somewhere.

author: Leadfootin
author_rank: Contributor
timestamp: November 06, 2014, 03:37:07 pm
content: Unfortunately no magic button. I suspect the coin cell maintained cpu memory and I may need source code to get this unit back working.

author: LA7SJA
author_rank: Regular Contributor
timestamp: November 06, 2014, 08:47:20 pm
content: This is from the (l)users manual 9.3 "User Maintenance"You can revitalize a battery pack with too low capacity asfollows:1. Reset the ScopeMeter test tool ( + ), and (ON-OFF)ensure that the test tool is battery operated.2. Press [MIN-MAX] to activate the Meter Min Max recordingmode.This disables the battery save feature when no key entry ismade for 5 minutes. Wait until the test tool is automaticallyturned off. When it is turned off, the batteries arecompletely discharged. Depending on the condition of thebatteries, the discharging can last up to 8 hours.3. When the test tool is turned off, connect the PowerAdapter/Battery Charger PM8907 to the test tool andto local line power.4. Charge for more than 21 hours.5. Repeat steps 1 through 4 once moreThe battery is not responsible for the program (it's in flash memory) memory only setup and time date RTC. I only have the 93, 95, 97 service manual but this is so differnt from the Fluke 91,92,96,99,105B ScopeMeter Serie II that I have so I think it's not to any helpJohan-Fredrik

author: Leadfootin
author_rank: Contributor
timestamp: November 06, 2014, 09:20:18 pm
content: Johan,Thanks but I have already tried that route. Unfortunately the unit simply won't turn on whether by battery or power adapter. I found the users manual on line but no service manual which may give me what I need. At least the service manual will let me determine if it really is bricked. The unit happens to be in excellent condition otherwise and I also have a 97 automotive version which comes in handy.Peter

author: LA7SJA
author_rank: Regular Contributor
timestamp: November 06, 2014, 10:56:48 pm
content: I know this sound stupid but I have experienced that it is very hard du get the charging plug in with the rubber protection on, so I just have to ask: What is the voltage on the battery pack and have you tried the unit with 4 D-Cells alkalines? Now I am officialy out off longshootsand soon I have to boot my brain.Johan-Fredrik

author: Leadfootin
author_rank: Contributor
timestamp: November 07, 2014, 12:59:28 am
content: Four new batteries, charger, battery pack from 97 and still no results.Need another step to try.

author: Shock
author_rank: Super Contributor
timestamp: November 07, 2014, 10:12:17 am
content: Check current draw under different scenarios. Is the battery being charged, or fluctuate when you hit the power button etc.

author: Leadfootin
author_rank: Contributor
timestamp: November 08, 2014, 03:21:54 pm
content: Shock,There is power to switch and LCD drive circuit. From notes by test points (white squares around unconnected contacts) on board there appears to be a reset procedure of some sort. Don't know which contact to connect to which other one!Peter

author: Shock
author_rank: Super Contributor
timestamp: November 08, 2014, 04:11:47 pm
content: Quote from: Leadfootin on November 08, 2014, 03:21:54 pmCheck how much current is drawn on the battery just sitting there and check the voltage to see if it's been fully charged. Then voltage and current on power adapter (on the DC side), both when the battery is connected and disconnected. You can also see if the voltage steps up on the battery when the power adapter is connected.Double check the coin cell battery you replaced is good. I'm not sure of the operation of this model so you may want to have at least the battery or power adapter connected when you do that, if you're not going to short anything out that is. When you replaced it before what order did you do things in?If you can't get a schematic then you will have to provide clear photos of the PCB (both sides if required) so we can see the circuit layout to assist. If the power button is of the standby variety you need to next measure where power is getting to.

author: Shock
author_rank: Super Contributor
timestamp: November 08, 2014, 04:17:55 pm
content: Actually Dave did a video last year on this model.

author: Shock
author_rank: Super Contributor
timestamp: November 08, 2014, 04:29:50 pm
content: http://assets.fluke.com/manuals/scopemt2umeng0000.pdfJust read your updated message, ok so it does have power.Read up on the manual I'm assuming you have lost the config replacing your batteries.Perform a master reset if there isn't anything better in the manuals. I've not read it fully so check this all out yourself.

author: Leadfootin
author_rank: Contributor
timestamp: November 08, 2014, 05:38:20 pm
content: How does one perform a master reset?

author: TopLoser
author_rank: Unknown
timestamp: November 08, 2014, 05:45:30 pm
content: Quote from: Leadfootin on November 08, 2014, 05:38:20 pmPress F5 and the ON/OFF button to power it up and reset it.

author: Leadfootin
author_rank: Contributor
timestamp: November 08, 2014, 06:24:50 pm
content: No luck. Boards are same as tear down video. Checked power switch function and problem seems to be that on/off circuit not latching and or sending signal to main switching power supply circuits.Looks like I will definitely need the service manual.