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Anyone up for Transformer Rewind?

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Hi,

First I want to say, I'm not quite sure where to post this, it seems to me that the DIY section is where it should go, but I'm not sure, so forgive me if I am wrong...

OK, I have a very rare turntable that has a 100v transformer. I need it to be rewound for 120v. It would require re-winding the primary coil I think.

Is there anyone on this forum that can help me out with this?

If you think you are the guy, let me know and I'll provide pictures of the Transformer. It's very standard.

Thanks a lot,
-Matt
 
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So it has a 100V primary (Japan maybe?) and you want it to run on 120V input?

There might be other ways of doing that. A bucking transformer or a Variac for example. Much easier to accomplish and the TT stays original. Just a thought.
 
toxcrusadr said:
So it has a 100V primary (Japan maybe?) and you want it to run on 120V input?

There might be other ways of doing that. A bucking transformer or a Variac for example. Much easier to accomplish and the TT stays original. Just a thought.
Click to expand...

Yes, It is Japanese. I am in America. It belongs with a set of US stereo component seperates:

index.php


Everything is US except for the TT which was too hard to find over here. I do not want to use an external converter, as the components would no longer be all the same. It works on 120v but some features don't work, and I've checked this is due to the transformer outputting too much voltage/current for the system.

I know this may seem overkill, but it is very important to me to get this right.
 
I guess I don't see using a bucking transformer as not getting it right. It is a very good solution that gets the voltage 'right' and is economical.

If the secondary is wound as an outer layer of the transformer, maybe you can remove some turns to get a lower secondary voltage.
Good luck,
John
 
A tt is a very low demand electrical component. Maybe you can find a transformer that will take the 120 you have and spit out the same voltage(s) that the tt needs to operate. This would be a transformer swap inside the unit. Now if you insist on the using the same transformer and rewinding it. there are places that do that but I haven't seen folks here discussing doing it themselves. Not that it hasn't happened. Most just use a separate transformer for this kind of power. I understand you not wanting to go that route.
 
What are the transformer specs? It would most likely be much easier and cheaper to simply replace the transformer with a similar one having a 120V primary, as opposed to winding a new one. You won't be able to re-wind the existing, because it is most likely varnish impregnated, and you'll destroy it trying to get it apart.
 
I would not be plugging it into 120V. It will soon be toast! What's wrong with an external step down transformer?
 
I hadn't thought about the varnish and the fact that it will be difficult to unwind. That's a bit of a non-starter.

Good advice about finding an equivalent transformer with 120V input though. Are there any numbers printed on the transformer? Might lead to specs, which would make it very easy to replace. You could keep the old one on hand (labeled of course) for posterity.

Sometimes we get too rigid about keeping things original. When I started restoring antique radios, it bothered me that the newer caps were 400 and 600V where the originals were 150 or 200V. I wanted to maintain the same specs. Well, it was hard to do, and completely unnecessary. I don't worry about it now.
 
A 120/24V transformer in buck mode should solve it nicely. Measure the existing line voltage. Subtract 24V (or more) from that and I'd bet that the voltage is so close to 100V that it wouldn't matter.

I would also guess that a turntable might draw a maximum of 20W on a really bad day, so a very small transformer (40VA) wold get it done with safety factor.

Something like THIS could get it done.
 
I agree with those suggesting replacing the transformer inside the TT. It will be cheaper than rewinding the 100V transformer.

A TT usually has one single secondary, and a small transformer (what means a cheap transformer). I'd check the secondary voltage needed and try to find a 120V transformer that fits inside the chassis.
 
maxhifi said:
What are the transformer specs? It would most likely be much easier and cheaper to simply replace the transformer with a similar one having a 120V primary, as opposed to winding a new one. You won't be able to re-wind the existing, because it is most likely varnish impregnated, and you'll destroy it trying to get it apart.
Click to expand...

This is a good suggestion to the OPS quest.
 
Ok, I've seen many recommending replacing the transformer inside the TT. That was my first choice, but I couldn't find an equivalent transformer. It's originally 100v to 9.6V + 12V. Two Red wires for 12V, two orange wires for 9.6v, and a black wire (center tap?) So I need a 120V to 9.6V + 12V.

It's also very thin, meaning it's not tall but it's very wide. (like a traditional transformer), it's probably about 1"-1.5" high... I'll post a picture tomorrow, I have to take the unit apart again... It would be like if you stepped on a normal transformer and squashed it to half of it's height. :eek:

If anyone can find a transformer like what I've described, I will absolutely replace it. (once again, pictures coming soon)

Now a bucking transformer, I have to admit, I don't really know what that is. :confused: If it's an internal fix, I'm willing to give it a try.

It's actually 10W max BTW.

Thanks everyone for the replies, I hope to get this done soon! :)
 
Google 'how to wire a bucking transformer'. Basically you take one lead of the primary and connect it to one lead of the secondary, and the other two leads are In and Out for your AC line. ItThe induction from the secondary winding works either with or against the incoming power, so you get 120 + or -X where X is the voltage rating of the secondary. Just have to make sure it's a hefty enough transformer that it can take the power throughput. That's the VA rating. Antique radio guys (and tube stereo fans) use them to cut down today's high supply voltages to 110V to prolong the life of tubes etc.
 
Probably best to mount something like that in a small box that plugs into the wall, and has an outlet on it for the TT. If you decide to go that route.
 
If you post some photos and a schematic of the power supply, I could give some more specific help. At the moment I am thinking a small torroid is probably the way to go, plenty of companies out there will make one custom.

It may also be possible to slightly modify the power supply to use a different voltage transformer. Most likely the turntable uses plus and minus 12V for the motor, and 5V for logic.
 
Personally, I wouldn't go rewinding the transformer because it could be a nightmare project and seems unnecessary. If it needs 100v on the primary, then give it 100v on the primary- either with a variac or by using an external bucking transformer.

I'm a little confused when you say "I do not want to use an external converter, as the components would no longer be all the same. It works on 120v but some features don't work, and I've checked this is due to the transformer outputting too much voltage/current for the system."

You'd basically just be plugging the TT into a different outlet that's providing 100v AC. The rest of the US made components would be plugged directly into the wall (or a power strip) that would provide the usual 120v.
 
Why wouldn't one of those step down power supplies work? Lots of them for sale. Many have a switch to select 100,110,120v,.etc. output. Some switch the primary voltage. Just plug the box into the wall and select desired output voltage.
 
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