I've got an Antek AS-2T350 transformer that I'm concerned has been damaged. It's HV winding was initially hooked up incorrectly to the rectifier. Do to my inexperience and Anteks lack of using different colored leads, I managed to short one secondary rather than configure as a CT. The fuse blew immediately when first powered. I went through a three more fuses before I narrowed it down. When all was disconnected the voltages on all secondaries looked good. Then I attempted to series connect the secondaries for CT and I only get low voltage. I've disconnected the CT again and now every secondary winding output is very low. The 350V are about 3-4Vac. The 6.3V windings are about 1VAC.
So, is there a simple test I can do to confirm I've killed this thing? Or are these measurements all the confirmation I need?
I was expecting that only the shorted secondary would have been damaged, but it seems all four secondary windings are.
Thanks for any input.
So, is there a simple test I can do to confirm I've killed this thing? Or are these measurements all the confirmation I need?
I was expecting that only the shorted secondary would have been damaged, but it seems all four secondary windings are.
Thanks for any input.
Hi,
Disconnect everything and test the continuity of each winding, and also make sure there is no continuity where there should not be any (between different windings). You can also measure the DC resistance of the two primaries and the two main secondaries (to make sure they are close to the values shown on the data sheet).
If it passes all these tests, it would seem to be good, but that would leave the low voltages you measured as a puzzle. The short on the secondary could have damaged the primary winding (as the short is reflected onto the primary by transformer action).
If it fails any of these tests - it is a dead one.
Good luck.
Malcolm
Disconnect everything and test the continuity of each winding, and also make sure there is no continuity where there should not be any (between different windings). You can also measure the DC resistance of the two primaries and the two main secondaries (to make sure they are close to the values shown on the data sheet).
If it passes all these tests, it would seem to be good, but that would leave the low voltages you measured as a puzzle. The short on the secondary could have damaged the primary winding (as the short is reflected onto the primary by transformer action).
If it fails any of these tests - it is a dead one.
Good luck.
Malcolm
Bad power switch, fuse holder or other wiring? Provided the fuse was correctly sized it is not very likely that the transformer is damaged, although not impossible. (These transformers are pretty rugged in my experience)
Thanks for the tips guys. The fuse was sized for the circuit but all my testing was done with no tubes ever installed. So I'm fairly certain the damage would be from me shorting one of the secondary windings.
Malcolm: The continuity is what I'd expect for the HV windings, however one has a resistance of 72R asper the datasheet, but the other is 69R.
The filament windings have continuity as expected.
I can not detect any continuity where there should be none.
I connected a new AC inlet/fuse to a single primary winding and taped off the other primary. The voltage on the secondary was still very low, about 4Vac. Next I switched connections to the other primary and taped off the unused primary. This time a 0.5A fuse blew immediately. I think this is confirmation of a short.
Malcolm: The continuity is what I'd expect for the HV windings, however one has a resistance of 72R asper the datasheet, but the other is 69R.
The filament windings have continuity as expected.
I can not detect any continuity where there should be none.
I connected a new AC inlet/fuse to a single primary winding and taped off the other primary. The voltage on the secondary was still very low, about 4Vac. Next I switched connections to the other primary and taped off the unused primary. This time a 0.5A fuse blew immediately. I think this is confirmation of a short.
Hi,
From the symptoms, it sounds to me like the initial short on the secondary output has caused excessive current on the primary. The overheating of the primary may have created a short between turns of one of the primary windings. When you energize this faulted primary it draws high current and blows the fuse.
But when you energize via the other primary, the faulted primary is acting a shorted winding, dragging the secondary voltages down.
To check this you could measure the DC resistance of each of the two primaries, but at a nominal 4.3 ohms it would require a fairly accurate multi-meter. If I am right one of the primaries would read close to 4.3 ohms and the other would read low.
Does sound like its dead though, unfortunately.
Malcolm
From the symptoms, it sounds to me like the initial short on the secondary output has caused excessive current on the primary. The overheating of the primary may have created a short between turns of one of the primary windings. When you energize this faulted primary it draws high current and blows the fuse.
But when you energize via the other primary, the faulted primary is acting a shorted winding, dragging the secondary voltages down.
To check this you could measure the DC resistance of each of the two primaries, but at a nominal 4.3 ohms it would require a fairly accurate multi-meter. If I am right one of the primaries would read close to 4.3 ohms and the other would read low.
Does sound like its dead though, unfortunately.
Malcolm
As kevinkr noted, these are really very rugged units, so it seems to me unlikely that if properly fused, you damaged the transformer. Since they use the same color wires for both hv and lv secondaries, and primaries, is it possible you have a phasing issue (using one wire from each of two different secondaries and only measuring leakage)? Blowing a 1/2 amp fuse, especially if it is a fast blow fuse, doesn't seem outlandish given that during the first half cycle of ac input, the primary will show a very low impedance. Try a 1 amp slow blow, or even better, place a 60-100 watt light bulb in series with the primary. Remember, these are designed to have both primaries in parallel for 120vac use. FWIW, I have used nine of these, in various sizes, and all have proven very reliable, cool running units.
One other point, if you have the antek metal case, you must be careful to attach it to the chassis via the center bolt only - if you use the center bolt and attach the can to the chassis at other points, you will have a one turn shorted winding, which will certainly blow a properly sized fuse.
As Jim says, the 0.5 amp fuse seems like a low value here. When you power up a transformer there is a high inrush current, which varies a lot from one switch-on event to the next. (It depends on the point in time of the mains waveform when the switch closes, in combination with any residual magnetization of the core from the last time it was used.) Slow blow fuses are therefore used (the inrush current settles down to a steady state after about 10 to 30 mains cycles). I agree that a 1 amp slow-blow fuse would be better.
Hope there is life in there after all !
Malcolm
Hope there is life in there after all !
Malcolm
Thanks again Malcolm. I don't doubt these are rugged transformers generally. However I ignorantly connected it up wrong the first few times and continually shorted out that one secondary. The Primany resistance looks good/equal between the two primaries. But powering the one primary blows the fuse.
Thanks for your thoughts Jim. This is not a phase issue at this point as all secondaries are separated. Regarding the cover, I haven't installed one yet but intend to do so when I get a replacement transformer. How do I prevent the cover from shorting to the chassis? It seems that trusting the painted surface alone is not wise. Would I need to insulate the cover's edge somehow?
I'll be ordering a new transformer shortly.
Thanks for your thoughts Jim. This is not a phase issue at this point as all secondaries are separated. Regarding the cover, I haven't installed one yet but intend to do so when I get a replacement transformer. How do I prevent the cover from shorting to the chassis? It seems that trusting the painted surface alone is not wise. Would I need to insulate the cover's edge somehow?
I'll be ordering a new transformer shortly.
Hi,
I'm fairly perplexed! I can't see where a solid fault could be, based on the various tests. Perhaps there is an intermittent fault, which gets activated by the high voltage when you apply the 115 volt mains, but is not activated by the low voltage involved the DC resistance test.
If you do any more tests let us know.
Best regards,
Malcolm
I'm fairly perplexed! I can't see where a solid fault could be, based on the various tests. Perhaps there is an intermittent fault, which gets activated by the high voltage when you apply the 115 volt mains, but is not activated by the low voltage involved the DC resistance test.
If you do any more tests let us know.
Best regards,
Malcolm
i was given a 300va antek, the primary windings were open,
when i unwinded the secondary to reveal the primary
windings i discovered that the primary wires were cut.
i suspected that during production, somehow the traffo
was dropped and landed on an edge...
when i unwinded the secondary to reveal the primary
windings i discovered that the primary wires were cut.
i suspected that during production, somehow the traffo
was dropped and landed on an edge...
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