Re: [a/s] Maintenance questions-Univolt Convertor

[bjacobs <bjacobs@xxxxxxxxxxxxxxxxxxx>]

Don:

	The Univolt is one of the simplest power converters you can find.  It
is a ferro-magnetic resonance power unit.  If it hums, it can probably
be repaired easily as there are only 3 components in it.

	The three components are
	1. The transformer
		In your unit, since you say it is humming, let us assume that it is working.
	2.  The capacitor.
		I would assume that this is bad.  In my 76, I had to replace it
last year.  They just dry up.  It is the nature of the beast. 
	3.  Diodes
		These are mounted on a heat sink.  They can be checked with a ohmmeter.

	To check the diodes, do the following:

	1.  Unplug the Univolt
	2.  Take the cover off
	3.  Find the diodes (there should be 2 of them mounted on a heat sink (a heat 		sink is a piece of aluminum or other metal with fins on it to dissipate heat)
	4.  With your ohm meter set to read ohms, measure the resistance of a diode.  		Then turn the leads of the ohm meter around and measure the resistance 			again.  What I mean is put the red wire of the meter on terminal 1 and 			the black wire of the meter on terminal 2 and measure the resistance 			and then put the black wire of the meter on terminal 1 and the red wire 		of the meter on terminal 2 and measure it again.  One way, there should 		be great resistance and the other way, there should be low resistance.
		Do this to the other diode.  It should read about the same.
	5.  If the diodes check out as mentioned above, (they are not built proof, 		but next to it,) I would not expect them to be bad, only the capacitor 			is left. (We have assumed that a humming transformer is working 			transformer.)  You do not have the equipment to check it and the best way then 
        is to replace it.  It should cost about $25 - $35 and can be
	found in a place that does motor work.  (A motor rewind shop, an air conditioner
        shop, an appliance repair shop.)  Before you take it out, short the two terminals
        with a screw driver.  This will discharge any power that may be in it.
	6.  If you can not fine the right capacitor, (mine was 25uF at 600VAC)it would 		be ok to use 2 that add up to 24 or 25 uF.  The 600VAC rating is 			standard and you should not have any trouble with it.  Take the old 			capacitor with you and tell the salesperson you want "one of these."
	7.  Put everything back together and plug it in.  
	8.  I would suggest that while you have the unit apart, install a switch in the		110 volt line.  The Univolt does not have to run all the time.  It just 		waists electric.  When the trailer is plugged in all winter,  you need 			to charge the battery once or twice a month.  When you are traveling, 			leave it on.  Also, the output of the my Univolt is 11.5 volts not 12 			volt, because of this, over charging the battery is minimal.  A real 			good idea.