Need advice about Battery charger for motor home

Thread Starter

Rennieaj

Joined May 6, 2018
49
Hi All,
Im hoping you can help, first off, i do have some electronic experience so i can solder, use a meter etc.
I have been given a 230vAC in to 14.8VDC battery charger for a motorhome to try to repair for my uncle, its an itallian one so i couldnt find much online about it.
basically, im getting no output, i was wondering if anyone could point me in the area for the common faults for such devices, i.e components and how to check them.
please see attached photos.
many thanks
 

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Dodgydave

Joined Jun 22, 2012
10,050
Ok looks like a switchmode and a linear transformer combination, what AC voltage do you have out of the Grey Transformer (top right) and then out of the bridge rectifier ( 4 diodes next to it) DC .?

Any model number?

Also can you take pictures of the tracks.
 

Thread Starter

Rennieaj

Joined May 6, 2018
49
Ok looks like a switchmode and a linear transformer combination, what AC voltage do you have out of the Grey Transformer (top right) and then out of the bridge rectifier ( 4 diodes next to it) DC .?

Any model number?

Also can you take pictures of the tracks.
Hi Dave thanks for your reply,
Im measuring around 5V DC on the 2 outer pins of the grey transformer (the meter probe is pointing to the pins on the attached photo) ive also attached a photo of the outside of the unit. where do i measure the voltage from the rectifier on the diodes?
 

Attachments

Thread Starter

Rennieaj

Joined May 6, 2018
49
Ok looks like a switchmode and a linear transformer combination, what AC voltage do you have out of the Grey Transformer (top right) and then out of the bridge rectifier ( 4 diodes next to it) DC .?

Any model number?

Also can you take pictures of the tracks.
im getting between 11 and 12 v DC across the diodes
 

Dodgydave

Joined Jun 22, 2012
10,050
Ok if you're getting 19V on 1,2 then you should definitely be getting voltage across C and D , as it's the output from the bridge rectifier.
 

LesJones

Joined Jan 8, 2017
3,477
"D" is the etch that the anode end of the middle two of the four diodes connect to. You can touch your meter probes on either of the solder connections where the anode ends of the middle two diodes are soldered to the track. Similarly for point "C" you can touch your meter probe to either of the cathodes of the outer two diodes are soldered to the track. I would expect you to get a DC reading of about 27 volts. (D should be negative and C positive.)

Les.
 

LesJones

Joined Jan 8, 2017
3,477
The TO220 device on the heatsink will be a voltage regulator IC. (Probably an LM78xx series) The negative output of the bridge goes to the center pin of this regulator and the positive output to the right hand pin. (This is in the picture of the etch side of the main board in post #12.) Measure the voltage between the middle pin and the left hand pin. Also read the part number of the voltage regulator so we can check the is giving the rated voltage output.
One thing that you may not be aware of is that some battery chargers need to see a voltage from the battery it is connected to before attempting to charge the battery. This is to protect the charger from reverse polarity or a battery of the wrong voltage.
I don't think your electrical knowledge will be enough to go much further with tracing the fault as you did not even understand that the anodes of the two diodes was the same point electrically. (Post #15) You would need to be able to trace out all or part of the schematic for us to be able to suggest further tests. Also working on switched mode power supplies is not safe if you do not understand what you are doing.

Les.
 

LesJones

Joined Jan 8, 2017
3,477
It is a 12 volt regulator so 11.9 volts is OK. Have you tried connecting the output to a 24 volt battery that is not totally discharged. (I.E terminal voltage at least 20 volts.)

Les.
 
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