How to find a replacement for massage chair transformer STL0219000 (110v to 24v)

[Buk]

If you measure the gauge of the wires on the primary, and its resistance, you can calculate the number of turns pretty accurately.

Assuming that the secondary has gone open or shirt circuit, you won't be able to apply the same there, but it doesn't look like it would be too hard to disasseble the cores. Given the (visual) guage of the wire relative to the coil, it wouldn't be too hard to estimate -- or even tease apart and count -- the number of truns in the secondary.

All that is then left is the tertiary tap. That would require unwinding -- counting as you go -- to find where the tap tees in. Having done that, you could purchase the right gauge wire and rewind it.

 

[Nigel Goodwin]

Well that sounds like it's going to meet all relevant safety standards - and no chance whatsoever of your chair bursting in to flames

 

[JimB]

From a quick calculation, it looks to be about 87VA.

Going on Nigels advice and comparing with this 75VA transformer:

RS PRO 75VA 2 Output Chassis Mounting Transformer, 50V ac | RS

uk.rs-online.com

and this 100VA transformer:

RS PRO 100VA 2 Output Chassis Mounting Transformer, 24V ac, IEC 61558-2-6 | RS

uk.rs-online.com

I would say that a 75VA transformer would do the job.

JimB

 

[Kkwcheng]

Thank you all for your gracious help. Nigel for suggesting the website and JimB for going the extra mile to provide more insights and recommendation. Thank you Bud as well but to be honest I can’t trust myself to perform what you outlined accurately haha. You are clearly more “experienced” than me on this. I’ll give the 75VA a go and post here when I have it installed. That’s assuming I can figure out how to wire up the transformer!

 

[Kkwcheng]

From a quick calculation, it looks to be about 87VA.

Going on Nigels advice and comparing with this 75VA transformer:

RS PRO 75VA 2 Output Chassis Mounting Transformer, 50V ac | RS

uk.rs-online.com

and this 100VA transformer:

RS PRO 100VA 2 Output Chassis Mounting Transformer, 24V ac, IEC 61558-2-6 | RS

uk.rs-online.com

I would say that a 75VA transformer would do the job.

JimB

Hi JimB,
I wanted to just double check. The link you had included for the 75VA is for a 230V transformer right? I would need to find one similar but for 110V right?

 

[Nigel Goodwin]

Hi JimB,
I wanted to just double check. The link you had included for the 75VA is for a 230V transformer right? I would need to find one similar but for 110V right?

Voltage makes no difference, 75VA is 75VA - many transformers have taps, or double primary windings, for connection to 230 or 110.

RS list a number of such types, such as this one:

RS PRO 50VA 2 Output Chassis Mounting Transformer, 24V ac | RS

uk.rs-online.com

However, they don't seem to list 75VA ones.

But obtaining a transformer from your own country is probably the best idea.

 

[JimB]

I would need to find one similar but for 110V right?

Yes.
I was just using that transformer for a physical size comparison.

As Nigel said.

JimB

 

[Buk]

Have you tried putting a meter across the primary and secondary coils yet?

 

[Nigel Goodwin]

Have you tried putting a meter across the primary and secondary coils yet?

???????? - doesn't seem a lot of point - and it's clearly marked 110V 24V

existing one is broken (charred and blackened)

 

[Buk]

it's clearly marked 110V 24V

Yes. I read that too.

existing one is broken (charred and blackened)

And that.

But before I plugged a new one in, I think I'd rather like to know why the old one failed.

And key to that might be whether it is the primary or secondary coils that failed.

10 seconds with a meter....

 

[Nigel Goodwin]

Yes. I read that too.


And that.

But before I plugged a new one in, I think I'd rather like to know why the old one failed.

And key to that might be whether it is the primary or secondary coils that failed.

10 seconds with a meter....

It's unlikely to help - a cooked transformer will fry until the primary dies, even if the secondary has the shorted turns, and measuring the resistance of the coils isn't going to be very informative.

More of an issue, and well worth testing, is what the transformer feeds - in case the rectifiers (or something else) has gone short - you would expect there to be a fuse, but there might not be, and they may depend on the transformers internal thermal fuse to blow in case of a secondary failure.

 

[Buk]

It's unlikely to help - a cooked transformer will fry until the primary dies, even if the secondary has the shorted turns, and measuring the resistance of the coils isn't going to be very informative.

Absolutely. Why waste 10 seconds.

 

[Nigel Goodwin]

Absolutely. Why waste 10 seconds.

For absolutely no purpose certainly.

 

[Buk]

Enjoy Nigel's garden kkwcheng; the path is quite winding.