Fluke 91 Scopemeter - bricked?

[Leadfootin]

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?

[obd.tech]

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

[Leadfootin]

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.

[Leadfootin]

Anyone have a service manual? Section on changing internal battery should have the info I need.

Thanks,
Peter

[Alex Eisenhut]

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.

I'd look for that special reset button recessed somewhere.

[Leadfootin]

Unfortunately no magic button. I suspect the coin cell maintained cpu memory and I may need source code to get this unit back working.

[LA7SJA]

This is from the (l)users manual 9.3 "User Maintenance"

You can revitalize a battery pack with too low capacity as
follows:
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 recording
mode.
This disables the battery save feature when no key entry is
made for 5 minutes. Wait until the test tool is automatically
turned off. When it is turned off, the batteries are
completely discharged. Depending on the condition of the
batteries, the discharging can last up to 8 hours.
3. When the test tool is turned off, connect the Power
Adapter/Battery Charger PM8907 to the test tool and
to local line power.
4. Charge for more than 21 hours.
5. Repeat steps 1 through 4 once more

The 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 help

Johan-Fredrik

[Leadfootin]

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

[LA7SJA]

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 longshoots  and soon I have to boot my brain.

Johan-Fredrik

[Leadfootin]

Four new batteries, charger, battery pack from 97 and still no results.
Need another step to try.

[Shock]

Check current draw under different scenarios. Is the battery being charged, or fluctuate when you hit the power button etc.

[Leadfootin]

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

[Shock]

Shock,

Just checked, no power to switch, problem appears to be in power supply circuit.

Peter

Check 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.

[Shock]

Actually Dave did a video last year on this model.

[Shock]

http://assets.fluke.com/manuals/scopemt2umeng0000.pdf

Just 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.

[Leadfootin]

How does one perform a master reset?

[TopLoser]

How does one perform a master reset?

Press F5 and the ON/OFF button to power it up and reset it.

[Leadfootin]

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.