Author Topic: Canon CA-920 batery charger/DC power supply repair  (Read 2411 times)

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Offline salamander

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Canon CA-920 batery charger/DC power supply repair
« on: April 14, 2015, 02:04:10 pm »
Hi, today I plugged in a borrowed Canon CA-920 (from Canon XM2 camera) and there was nothing ... I checked the input wiring etc. but nothing wrong. (The adapter worked a few days ago)

So, I disassembled the unit, but I am unable to find anything wrong with it. There is a large text about replacing the fuses ... but for me (I am really not an electrical engineer) there aren't any (at least obvious).
I checked the lines, and there seems to be no power at all on the secondary side.
Please help me, what can be wrong? I am quite desperate, because I have to return the camera in a few weeks and the guy will be pissed off if the adapter will not be working :( (Yeah, and I need the camera for my project)
 

Offline Grapsus

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Re: Canon CA-920 batery charger/DC power supply repair
« Reply #1 on: April 14, 2015, 02:54:42 pm »
The fuse is the black cylinder near the mains input socket with "Bel T2A 250V" written on it. Check the fuse for continuity. Maybe you shouldn't be touching this PSU if you're not sure about it. That big 400V capacitor could hurt you badly if not discharged properly.
 

Offline salamander

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Re: Canon CA-920 batery charger/DC power supply repair
« Reply #2 on: April 14, 2015, 03:11:44 pm »
Main fuse seems to be OK, there is voltage on he primary side, I measured ~300V DC behind that rectifier, but there is literally nothing on the secondary.
 

Offline Grapsus

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Re: Canon CA-920 batery charger/DC power supply repair
« Reply #3 on: April 14, 2015, 03:32:05 pm »
The rectified 300V DC should then be switched into the primary at around 40 kHz by a chunky MOSFET. It must be the three-legged component attached to the heatsink near the big capacitor. If this mosfet is not running it's either because it's dead or it receives a wrong feedback. Again, be careful with the mains capacitor.

Edit: picture with the location of the mosfet that switches the primary.
« Last Edit: April 14, 2015, 03:36:37 pm by Grapsus »
 

Offline salamander

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Re: Canon CA-920 batery charger/DC power supply repair
« Reply #4 on: April 14, 2015, 04:09:24 pm »
Well, I will leave this to someone who knows what he's doing, I don't really feel safe probing this thing.

Thanks for the advice anyway
 

Online SeanB

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Re: Canon CA-920 batery charger/DC power supply repair
« Reply #5 on: April 14, 2015, 06:57:17 pm »
R4, R5 or R13 are open circuit. They are under the large brown capacitor on the mains side. Most likely the value is 470k 0.25W. They are the start up resistors for the power supply.
 


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