Fluke 199/225c repair Blown Part ID

[charliedelta]

My Fluke Scopemeter blew up while on charge. It was fully working.

I have disassembled it and found some evidence of a failed component that had severe overheating in the area.
I have attached a picture if you have a failed Fluke 199/225 PCB lying around that could help me ID the part before I start cleaning and tracing that would make life easy!

It smells like the classic fried capacitor smell, that fowl exploded capacitor smell. It does not look like a power diode/TVS nor is it an inductor(no evidence of copper wire.

It would be shame to throw it away since the whole PCB should be working. Just forget about Fluke for service or parts or anything they  make throw away fuse test instruments.


Can anyone ID the part so can attempt to change it and maybe get lucky? I would be also interested in buying a failed PCB that I can salvage parts from.

Thanks

[asis]

Hi,

Check external Power Adapter and CHARGER on PCB Scopemeter.

[charliedelta]

Thanks, I have a lot of work to do. Incredible that a tantalum capacitor shorting causes so much damage while sinking so much current to burn the PCB to black carbon. The lack of circuit protection by the Fluke designers is  suprising.

I will replace the capacitor with a 100uf 16V tantalum and see how that goes.
The Schottky diode B1C appears to be leaky. I have to confirm the tracks in the area. It is severely burnt. There is some tracks that may be broken from burning/cleaning up even though I was careful.

Thanks for your help.  I will check the charger.  Its reading 21 volts with a spec of 17.8v dc.

[asis]

Hi,

As far as I remember, an IRFZ44N MOSFET is installed in the external adapter, which acts as a current limiter.
To get to it, you need to open the power adapter.

Pay attention to the polarity of the voltage on the power plug!

[Per Hansson]

I will check the charger.  Its reading 21 volts with a spec of 17.8v dc.

Seems normal: I checked mine with no load and it reads 21.1v.

[Johnny10]

What was the cause of the explosion?
Was unit being used while on charger?

[asis]

....I'll get better

[charliedelta]

Thanks. I will check for that and test it.  It should have let that much  be sourced in a fault. The damage is really bad.

Hi,

As far as I remember, an IRFZ44N MOSFET is installed in the external adapter, which acts as a current limiter.
To get to it, you need to open the power adapter.

Pay attention to the polarity of the voltage on the power plug!

[charliedelta]

Thanks I have saved  that diagram.

....I'll get better

[charliedelta]

Thats the thing, there was no explosion. I generally run down and recharge the batteries now and again. I did exactly this and  was ready to pack it away and I got a hint of the bad smell. Then I tried to power it on. I initially thought that it was a failed battery and bought a new one. This new battery would not turn on the unit and I decided to investigate. I was working in the lab while it was charging, no pops, smells etc  Then when I look  at the damage, I am surprised that I could  not smell or hear something.  So this is a weird one to me. It may well be that the Fluke is so well sealed with the clam shell like assembly that it contained the smoke  and sound  because the fault was under the PCB.

Anyway if its a write off I am  willing to donate it to someone  who may have better luck with it. I know the meter and scope were 100% before the meltdown. Repairing through Fluke  can never be even contemplated they just charge too much. Even something like a battery change from them cost half of secondhand unit!

What was the cause of the explosion?
Was unit being used while on charger?