Replacement Isolation Transformer?

Thread Starter

Sosijdog

Joined Nov 11, 2009
10
Hi guys, i need some help to identify a suitable replacement for an isolation transformer. It is used on a garage door opening controller and it has blown a hole through the base of the transformer. This has happened twice and the company know it is a transformer fault. Unfortunately, a search of the number yeilds no results for a replacement and It appears to be obsolete? Possibly because of the age of the unit or because they fail so often? The only option is to purchase a new control board for a few hundred £’s.
So i guess the question is - does anyone know where i can purchase an equivalent or even a toroidal transformer in place of a PCB mounted unit? I feel uneasy about putting in a different transformer than standard but should this be ok if the ratings are correct?
I have posted a picture of the defective Block Transformer...
Any info would be much appreciated.
 

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SamR

Joined Mar 19, 2019
2,791
It's a step-down transformer. 230VAC to 12VAC rated 15VA which isn't very much. Any similar and rated 15VA or better will do.
 

MisterBill2

Joined Jan 23, 2018
7,309
Indeed it is a step-down transformer.although it also provides isolation. If you can find room to mount an open frame transformer I recommend that as a replacement. It may be called a 24 volt center tapped transformer with a 230 volt primary. An open farme one of equal rating will not be much larger, and it may stay a bit cooler without all that insulation to hold in the heat.
 

Thread Starter

Sosijdog

Joined Nov 11, 2009
10
Excellent info guys. Thanks for the replies. During my search they seemed to refer to these as “isolation transformers” hence why I referred to them as such.

SamR - you said 15VA “or better”... does that mean the VA rating is not crucial (as long as it is higher)? I would assume physical dimensions would be a determining factor in that instance. But that is good to know that a similar rated transformer will be ok. I think there is enough room for an open frame so i will look into that.

much appreciated.
 
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SamR

Joined Mar 19, 2019
2,791
VA rating is not crucial (as long as it is higher)?
Correct, although higher VA would be physically larger. There are several forms available. Single 2 wire or dual 4 wire primaries. Single 2 wire secondary, 3 wire center-tapped secondary, dual 4 wire secondary. Form does not matter as long as the primary and secondary voltages are correct and the VA rating is 15VA or higher. Considering that the original transformer failed, it might be advisable to increase the VA rating. Transformers that are in constant use typically do not fail. Open frames are typically used inside an enclosure and fully shielded transformers are used as standalones outside of enclosures.
 

MisterBill2

Joined Jan 23, 2018
7,309
Isolation transformers are usually 1:1 ratio, so you would be getting the mains voltage, 220, instead of the 24 volts center tapped. Damage would certainly result. Thus verifying the ratings is important indeed.You need to use your meter to verify the voltage prior to making that secondary winding connection.
 
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