Using a Hammond 278CX 800VCT 535mA. Starts to vibrate at about 75% of full primary voltage. Looking for other designs but not finding. NEED Something potted or maybe toroidal. HELP.
Antek makes good and inexpensive toroid transformers. I bet they have something with similar specs.
Did you have the transformer under load during this test? If so, how much load and was it a capacitor or choke input filter?
The 300 series from Hammond is much better but more expensive, of course. I gave up on the 200 series, too many issues. Singing windings, failed windings (out of the box!), etc. The Anteks are fine, a pain to mount but they do the job. You'll need to create a bridge rectifier, either SS or half SS, half tube rectifier.
https://www.antekinc.com/as-4t400-400va-400v-transformer/
https://www.antekinc.com/as-4t400-400va-400v-transformer/
I use two of them in a line-level Aikido preamp and they are silent. The only danger with toroids is if you have any significant DC offset in your AC power lines. Then they will hum. There are ways to fix this. Most of them time this is not a problem.
I think sometimes there is more of a current surge at switch-on (blew the fuse on a old PSU I had that had been modified from an EI transformer), but an inrush current limiter on the primary side solves that.
BTW just an update got a box end wrench on the through bolts nuts and really cinched them down. Not silent but alot quieter than before. Probably didn't need to order that toroid from Antek but will use with something.
I could be misremembering, but IIRC you need to be careful not to tighten the lams TOO much so that you don't compress them. But maybe that's not an issue... Glad it's quieter, anyway.
Well not sure bc tightening them down at all will compress the lams. Now if there is a spec then I would understand that. but what would be the detriment of having them too "tight". have less relative movement between the lams seems like it would be better. Now if you compromised the insulation between the lams then understand that. But if they are moving relative than that might compromise the insulation between lams more so. Open to learning something though.
I just seem to recall that you want to be careful not to bend the lams or compromise the insulation, as you say. That's all.
To me it looks like tightening the four compression bolts should have no affect on operation of the lams, other than to suppress magnetorestrictive vibrations. The laminations are meant to be aggressively compressed against each other to restrict micro airgaps, and those laminations overlap on successive layers to restrict such gaps further. The bellends are meant to uniformly pressure the laminations together to restrict such gaps, so in general the tighter the better.
Some aspects to consider could be:
Some aspects to consider could be:
- the bell-ends are a little cheap on their thickness, which may allow for more bending between the bolts.
- the fibre-washers or compression bolts may have relaxed since tightening in the factory, and so need re-torquing.
- the outermost lams on both sides may have some 'looser' portions allowing them to vibrate a titch more than if those lams were more securely supported (wedged) in place.
- the internal winding former may not be adequately supported (wedged) to the core, allowing the former to vibrate against the core.
- vibrations from core may be coupled to the chassis, which then accentuates the noise. Some use an isolation washer between chassis and mounting holes on bell-ends, but that can compromise electrical connection of transformer core/bell-ends to chassis for safety. Sometimes using washers or nuts to raise the transformer a bit away from the chassis can suppress electromagnetic coupling to the chassis, which may be a mechanism for vibration.
Last edited:
Just an update. After tightening there is still a very slight noise that I can hear. The lightest touch on the end bells stops it though. And I noticed that the bolts were not very tight form the factory. Maybe loosened up during shipping.
Antex might be cheap,but their regulation is low.that means less copper in the windings. You get what you pay for. 6.3vac @ 3 amps.its actually 6.08 vac. Worse on hv. That buzz is vibrating loose windings. Machine wound without correct tension. Want no buzz,buy japan or monolith magnetics.
The OP has a Hammond, and has recently reported no buzz for a particular fault-finding condition, so Antek(x) or any other recommendation now appears to be a non-issue.
I've never had a noise problem with Anteks. And though they are spec'd for 115VAC primaries, the output voltages have always been spot on. OTOH, I've had a good deal of trouble with the Hammond 200 series.