Antek Power Transformers

[Tage]

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

[defaced]

Yes, that is how you would do it.

I have had one in my prototyping rig for a couple of years now. Not bad iron for the price.

[oc disorder]

Hi Tage
Yes, by joining those two connections you are putting the two 325v windings in series to get 650v AC "centre tapped" and
"the join" is the centre tap.The polarity has to be observed so that the windings work together and not oppose.
Here you only need two diodes for full wave rectification

I drew the two alternative "wirings" for the mains input, the two windings in series for 230v and in parallel for 115v.

In the same way the two yellow and the two white wires could be joined for a 325v output at double the current
connecting them to a bridge rectifier and grounding the negative .

[Tage]

Thank you very much, I needed that re-assurance. They seem to be very affordable for toroidal transformers.

In the case of running the two secondary connections in parellel for more current output would the rectified voltage of the fulwave bridge be in the area of 325Vx1.2=390V

[defaced]

I think it will be higher than that (my 400v AC Antek gives me ~550v DC unloaded). If your transformer has similar characteristics to mine (big if), it'll be up around 450v DC unloaded.

[imaradiostar]

You'll get more efficient use of the transformer if you were to use the transformer with a full wave bridge rectifier and the windings in parallel but then you won't have an easy way to generate bias (except maybe a capacitive bias supply).

I've used antek pt's on a few builds with excellent results. They have all been low power (under 30 watts) but I'm hoping to use them for a high power build some day soon.

jamie

[R.G.]

You'll get more efficient use of the transformer if you were to use the transformer with a full wave bridge rectifier and the windings in parallel but then you won't have an easy way to generate bias (except maybe a capacitive bias supply).

Unlike E-I or C-C core transformers, toroids do offer a way to add another winding fairly safely and easily. Well, they do as long as they do not have the middle hole of the donut poured full of epoxy. You can thread wire through the hole, adding a winding. This is very tedious for hundreds of turns, but can be done. It's relatively safe as long as you can make sure to insulate the added winding from being cut or abraded or damaged by the mounting, which is usually a dished plate and center screw. It's a useful dodge for (1) low voltage (2) low current added secondaries. Magnet wire is fairly fragile and needs to be overwrapped with some kind of protective tape. Wire-wrap wire might work OK and be more robust.

The turns should be distributed completely around the toroid circumference.

Do not try this unless you can be certain you will not and can prevent damage to the wires and cause a shorted turn either in testing or in use. That makes for needlessly exciting results.

[exclamationmark]

Also, be sure NOT to connect the mounting bolt to two different surfaces (ie, both sides of chassis). It'll basically form one shorted loop, and quickly proceed to dump a couple hundred amps through your mounting bolt.

[R.G.]

Also, be sure NOT to connect the mounting bolt to two different surfaces (ie, both sides of chassis). It'll basically form one shorted loop, and quickly proceed to dump a couple hundred amps through your mounting bolt.

OH yeah. Accidentally connecting the mounting bolt into a closed loop with the chassis is one of the best ways to form a Light Emitting Chassis Bolt (LECB).

[Jag]

OH yeah. Accidentally connecting the mounting bolt into a closed loop with the chassis is one of the best ways to form a Light Emitting Chassis Bolt (LECB).

I just sprayed my Mac with coffee! LOL

[imaradiostar]

Unlike E-I or C-C core transformers, toroids do offer a way to add another winding fairly safely and easily. Well, they do as long as they do not have the middle hole of the donut poured full of epoxy. You can thread wire through the hole, adding a winding. This is very tedious for hundreds of turns, but can be done. It's relatively safe as long as you can make sure to insulate the added winding from being cut or abraded or damaged by the mounting, which is usually a dished plate and center screw. It's a useful dodge for (1) low voltage (2) low current added secondaries. Magnet wire is fairly fragile and needs to be overwrapped with some kind of protective tape. Wire-wrap wire might work OK and be more robust.

The turns should be distributed completely around the toroid circumference.

Do not try this unless you can be certain you will not and can prevent damage to the wires and cause a shorted turn either in testing or in use. That makes for needlessly exciting results.

I suggested adding windings once and no one seemed interested. It makes me happy that you suggested it.

jamie

[R.G.]

I suggested adding windings once and no one seemed interested. It makes me happy that you suggested it.

I missed that. You're right. Another winding is a good step if you can get it into the transformer.

The big problem with adding windings to a transformer is the impracticality of just physically getting them into the transformer in a way that's useful and durable. Toroids and the semi-toroid "flat pack" PCB mount transformers are about the only ones where there's room to get additional winding in without disturbing the critical primary-voltage safety insulation.

In my (literally!) decades-long quest to reverse engineer the old Thomas Vox amplifiers, I was able to measure the number of turns on the driver transformer by threading in many turns of fine wire in the spaces left at the end of the bobbins and get it to last long enough to measure the voltage ratios. This gave me the turns ratio and the turns since I knew how many turns I'd put in. But I broke a wire during the testing, not long after I'd gotten just enough information. (I think it was enough; we'll see. )

[Tage]

Thanks for the feedback. I'm planning to use it in a cathode biased 4 el34 type amp so I wasn't too concerned about a bias tap. On that note would adding that wining really be more feasible than capacitor coupling a bias supply?

[defaced]

Having been down the road of making that decision, I decided to see what was behind door number three. There I found the option of a second transformer just for bias. I had a PCB mounted 8v transformer in the drawer so I wired the secondary in parallel with the heaters. This gave about 90v AC on the primary which was manageable for bias. A 12v or 15v transformer would be a better chose since that would put you in the 60v to 50v AC range.

[Tage]

so you ran the 6.3 volts into the 8v transformers secondary and got 90 on the primary side. I never thought of trying that, I have a 16V transformer, so I'll keep that in mind in the future. but then again adding another transformer I could just get one to give me 60V at low current and I would be using up the same kind of space.