>I have an AL80B in which I "re-jumpered" the power supply
>for 220V since we have 200V/50Hz in Sweden.
>
>The problem is a very annoying "humming" sound, much louder
>than fans and everything else in the room. I estimate the
>sound to be about 100Hz. The amplifier works fine otherwise,
>and voltages seem to be OK. The fan itself is "quiet".
>
>Since I have not been able to test it on 60Hz AC, I would
>like some opinion if you think that this could have something
>to do with 50 vs 60Hz operation. Or, maybe the AL80 is known
>to be a "loud" amplifier (it's my first).
>
- I would try tightening the screws that hold the transformer
laminations together. If that does not quiet it down, you may need to
purchase a transformer that is designed to work satisfactorily on 50Hz
mains.
- Here in the States, MFJ-Ameritron has a seemingly well-deserved
reputation for marginal designs.
cheers, Mats
Rich---
R. L. Measures, 805-386-3734, AG6K
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