Hello,
One of my two recently purchased Sefram 7835 field meters has a problem related to the power management circuit. This circuit deals with running the device on the battery or PSU, as well as, charging of the battery.
The symptoms are:
- Sometimes the device behaves normal
- Sometimes it just switches off: sometimes I can switch it one again, sometimes it won't switch on again!
- When it does not switch on again, it helps to leave it charging (=heating up, the battery has charge and runs fine on the other device). After a while it will switch on by itself or at least tries to switch on (screen goes on/off and pressing the ON button will eventually turn the device on)
- When left alone, even without PSU connected, it sometimes goes on/off by itself
I have looked at the board and found that the capacitor next to a MOSFET has leaked. I don't think it is any glue. Take a look at the attached picture.
This same section has been changed (manually, I guess, in a previous repair) on the other device - so I think it is a problematic region of the PCB. It was by comparing both PCB's that I noticed that the other device has had the MOSFET replaced with another type, an extra wire added and one of the cap's replaced. Probably some traces had been corroded.
On this device, things don't look so bad.
I did clean the board a bit and the device started to behave normally, but today it is erratic again.
I think I need to replace the SANYO 68uF 20V 105ÂșC cap, but I fear that the MOSFET is not doing so well, either.
Now the question: what exact type is this MOSFET? I can read: 418 20P ON 03HL
418 --> Type?
ON --> Manufacturer?
20P --> ?
03HL --> Production date?
Can anyone tell me a replacement for this IC?
Also, from the pictures, would you agree that the orange stuff is leaked electrolyte from the CAP - very visible next to the Q100 print?
Is this electrolyte conductive? Could it be causing the erratic behaviour?
Can I replace this CAP (seems to be aluminium foil from what I read) with a generic no-brand 64uF/25V cap?
Thanks!
Regards,
Vitor