On Saturday, March 10, 2018 at 9:30:43 PM UTC-5, Phil Allison wrote:
wrote:
--------------------------
I'm particularly interested in how badly they ring.
What causes an audio
transformer to ring?
60Hz transformers hum,
** A lot of force comes from the 60Hz supply acting on anything
magnetic with a bunch of wire wound around it. This is single,
low frequency, forced vibration, not resonance.
You know, in AC solenoids a shorting ring is beneficial to keep
60 Hz buzzing to a minimum, as the shorting ring provides a CEMF!!!!
** However, solenoids and relays have moving parts - transformers do not, so are normally bolted up tight and run silent.
Had a Chinese made guitar amp here that would suddenly made a loud hum if laid over on its back, standing upright it was OK.
The four bolts holding the power transformer laminations together were barely finger tight. Soon fixed.
Good deal!
With scraplesss laminations, some xfmr cores aren't interleaved (laminations), but a butt (E & I) stack (Shell type), then the joint is welded.
Working with CVRs (Constant Voltage Regulators) where input can vary +/- 15% but output can only vary +/- 2% (generally used for large tube filaments), were a pain to adjust. Some got out the door out of spec, they were totally varnished. Typically, you remove lamination's from center leg to adjust output voltage, but no way to do it when totally varnished. I suggested to "drill" out the center leg on a drill press while testing!
Jack
.... Phil