Antek Power Transformers

[R.G.]

... so I wired the secondary in parallel with the heaters. This gave about 90v AC on the primary which was manageable for bias

Plus three points for clever response to the situation!
Congrats!

[Steve Conner]

Love the "Light Emitting Chassis Bolt" thing!

I've often added windings to toroid transformers. All of RG's comments ring true. I once used some old magnet wire with flaky insulation, nicked it during winding causing some shorted turns, and when I powered my new transformer up, the magic smoke went everywhere!

Since that experience, I use ordinary hookup wire, or even the thin Kynar insulated wire-wrap wire for low currents.

I wouldn't hesitate to use the inner conductors from "Romex" type house wiring to make a high current heater winding on a large toroid, either. At least that's what I'm probably going to do with that big medical grade isolation transformer I salvaged, when I use it as a PT...

Using a small transformer backwards for bias is a great idea. I remember seeing it in an old edition of the RSGB ham radio handbook.

[defaced]

So since we're talking about adding secondaries to the core, at what point does the core say "I can't take it anymore" and you can't add any more? 10% more VA, 20%... 30%? Or is it not that simple?

[Zozobra]

I have had a real dick ache ordering a PT from Antek. First there was a problem with the shipping fee which was my fault, then the damn thing got lost in the mail, then they were out of stock, then the stock didn't come in! Some 10 weeks or so later they're shipping me an alternative transformer which is probably a little better suited to what I want to do with it anyway. They do suck at communications, especially by email so phone them if you have any troubles. They do offer a lot of transformer for the cash so if this one does turn up I would use them again in the future as really, a lot of went wrong here was bad luck. Just thought I'd share.

[imaradiostar]

I'm lucky- they're nearby so I can get stuff from them pretty quickly and inexpensively. I'd imagine shipping across the pond is expensive.

Next time I order one of their toroids I'm going to wind my own bias windings.

Does anyone have an antek toroid laying around? I wonder how many windings it would take to make a decent amount of voltage?

jamie

[Zozobra]

$44 flat rate USPS and you can fit a few in a box too. Still much cheaper than anything I've seen over this way unfortunately.

[defaced]

Does anyone have an antek toroid laying around? I wonder how many windings it would take to make a decent amount of voltage?

Since they wind the heaters on the outside and we can count how many turns is equivalent to 6.3 volts, I'm guessing we could ballpark a number of turns required for X voltage knowing the number of turns of the heater winding. I'll count the number of turns on the two transformers I have (both 400VA) and report back.

[Steve Conner]

So since we're talking about adding secondaries to the core, at what point does the core say "I can't take it anymore" and you can't add any more? 10% more VA, 20%... 30%? Or is it not that simple?

RG might have a better explanation. But the way I see it, the core of a transformer doesn't care how much current is flowing in the windings. People say that you can saturate it by drawing too much current, but that's wrong. If you want to overload the core of a transformer, you have to apply too much voltage, like 160V into a 120V primary. Then the core will buzz a lot and get hot.

So when adding windings what you have to respect is the VA rating of the primary winding, so as not to overheat it. Say you had a 500VA transformer and you want to add a 6.3V heater winding to supply 10A. That's 63VA, so you should really only draw 437VA from the other secondary. Or you have to ask yourself if you'd be happy taking 563VA from a 500VA unit. If you even can calculate how many VA your rectifier is pulling per watt of DC delivered. I must admit that I don't even try, I measure it with a Kill-A-Watt plug-in power meter.

[defaced]

Thanks Steve. That makes sense.

I took a gander at one of my transformers and the heater secondary is 16 turns. So it looks like you'd need somewhere in the neighborhood of 160 turns to get 60ish volts.

[R.G.]

RG might have a better explanation. But the way I see it, the core of a transformer doesn't care how much current is flowing in the windings. People say that you can saturate it by drawing too much current, but that's wrong. If you want to overload the core of a transformer, you have to apply too much voltage, like 160V into a 120V primary. Then the core will buzz a lot and get hot.

I don't know that I could explain it better. The core doesn't care about secondary current, for sure, and it only really cares about primary current to the extent that there's DC in it or not. You can't saturate a core from the secondary, only from the primary by applying too much voltage and/or too low a frequency. I think people mistake overheating for saturation.

So when adding windings what you have to respect is the VA rating of the primary winding, so as not to overheat it.

Yep. Right on.

[Zozobra]

I hope my PT comes soon as I'm chomping at the bit to get building some stuff! There will no doubt be a thread started on the topic of does this bias supply look right to you? soon haha!

[Wombaticus]

I did a quick search for any threads on the transformers and didn't find much. I was wondering if anyone has used them and if you have could you help me understand the wiring methods for them. I'm just having some trouble understanding their images. As far as I can tell to make it a center tapped transformer in this case I would ground the first white secondary and the second yellow secondary? is this a correct method?

http://www.antekinc.com/pdf/AN-3T325.pdf

Tage,

I've used exactly that transformer in a recent two-phase rectifier 4x6L6 build, with great success. I get something like 420V under quiescent load with typical bias. I'm only using one of the two 6.3V taps (preamp heaters are DC supplied from another transformer), but it barely gets warm. Can't beat the price.

Cheers,

Paul

[loudthud]

Ran across this on ebay looking for some big heat sinks:

Enclosures, Power Supply items in Antek inc store on eBay!

Also has rack mount chassis.

[Tage]

Finaly ordered one of these up it's a 400VA 430 volt PT that I'm looking to get around 560V, loaded, from running the HV windings in parallel. I'm pretty stoked.

[Tage]

Hey so I finally got my Antek power transformer, model AS-4T430. turns out that it has 70 volt taps on both High voltage windings. So now I plan to run both High voltage windings in parallel and use a bridge rectifier. My question is do I connect both 70V taps together for my bias supply? or just use one?
I know the bias supply hardly draws any current so using just one should be an issue right?

Also is there and issue with elevating the heaters using the bias supply tap? just after the first filter for the bias supply? is 70V rectified gonna be too high of an elevation?