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-   -   Success! Univolt Repaired. (https://www.airforums.com/forums/f37/success-univolt-repaired-15096.html)

68LANDYACHT 01-05-2005 02:38 PM

Success! Univolt Repaired.
 
After researching this site for awhile, I decided to try and repair my dead Univolt. I acquired three 450 v. capacitors from a local A/C supply business and replaced the 650 v. originals. The told me at the A/C business that you cannot reduce the size of the capacitors, only increase the size. But, for 12 bucks and change I was going to try anyway. Well, the once dead Univolt immediately hummed to life after soldering in the new capacitors. It cranks out 12.8 volts which I think will be sufficient.

sander17 01-05-2005 02:54 PM

Capacitors
They were refering to the capacitance in microfarads. As long as you installed the correct value, the only concerns are the ruggedness of the housing (metal can) and the voltage rating. The maximum voltage seen by the capacitors is the peak-to-peak value of the 115 VAC, which is a lot less than the 450 V that yours are rated for. $8 for a couple of capacitors sure beats $200 for a new power supply.

raebaker06 01-06-2005 09:19 AM

Univolt repair
 
Quote:

Originally Posted by 68LANDYACHT
After researching this site for awhile, I decided to try and repair my dead Univolt. I acquired three 450 v. capacitors from a local A/C supply business and replaced the 650 v. originals. The told me at the A/C business that you cannot reduce the size of the capacitors, only increase the size. But, for 12 bucks and change I was going to try anyway. Well, the once dead Univolt immediately hummed to life after soldering in the new capacitors. It cranks out 12.8 volts which I think will be sufficient.


The transformer produces 6 VAC and that is supplied to the rectifier diodes. But there is in the circuit the cpacitors which turns it into a voltage doubler circuit....hence 12 V pulsin dc. the battery acts as a filter cpacitor stoing voltage to produce smooth DC Volts. This is a comm0on failure and your selection of 450 V cpacitors was sufficient to work.

I have done this on several units brought to my shop.

Rae Electronic Service Lab


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