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View Full Version : Yaqin MS23B Step Down Autotransformer for UK Mains?



pikebobstar
05-07-2015, 19:15
Hi All,

Thinking of using one of these for a stable 220V supply? http://uk.rs-online.com/web/p/autotransformers/2932656/

Will the amperage rating (1.6/0.8A) be sufficient.

I used one of these Autotransformers for a Little Dot Mk3 following an online recommendation and it worked a treat with no issues for a couple of years more or less constant use.

Your thoughts most welcome :)

awkwardbydesign
05-07-2015, 21:07
A smple and cheap method is to use a bucking transformer. This is what I and others have done. But a dropper resistor in the heater circuit may be all that is needed in the Yaqin. Anyway, here is some info on the bucking transformer. http://sound.westhost.com/articles/buck-xfmr.htm
I have made several of them, each in an oak box. Add a fuse if you like.

pikebobstar
12-07-2015, 13:47
Well, Just to advise I went again with the Block step down transformer so supplying the Yaqin with a regulated 220V power supply @ 0.8-1.6A and have noticed the unit is running cooler. Also, a slight whine I had from the transformer outer metal casing has gone. I cant be certain it's the difference in voltage/heat or to do with some hours now being put on it.

This little valve phono pre is just getting better and better as time goes on. Recommended.
Cheers

lurcher
12-07-2015, 14:04
Just to answer the original question, no the transformer in the first post is not suitable for producing 220v from 230v mains, its a 2:1 ratio so your amp is seeing 120v now. You would either need a custom would autoformer or use the bucking method shown.

awkwardbydesign
12-07-2015, 14:15
Just to answer the original question, no the transformer in the first post is not suitable for producing 220v from 230v mains, its a 2:1 ratio so your amp is seeing 120v now. You would either need a custom would autoformer or use the bucking method shown.
I just had another look at that transformer. It looks like a step-up! So 115v in and 115/220/230 or 240v out. So totally wrong. I missed that first time round. :doh:

lurcher
12-07-2015, 14:34
Actually, I just had a look as well, its misleading, the spec shows primary and secondary, but its described as a autoformer. I think it will just be a 0-115-220-230-240 autoformer. So I was wrong, it will be perfectly suitable to go from 240v to 220v

awkwardbydesign
12-07-2015, 17:55
..

pikebobstar
12-07-2015, 18:35
Hi and thanks for the comments/advice.

As I mentioned, I used this transformer to step down 240-220V on a Little Dot Mkiii headphone/preamp and it worked just fine for 2 years. Recently sold it and had no issue reported from the new buyer.

I have read the supplied data sheet cover to cover a few times and am certain it IS a step down autotransformer. I also believe the internal fuse in the Yaqin is 1A? according to its data sheet. So I guess it will match ok. Time will tell.

Thanks again