Electronics > Projects, Designs, and Technical Stuff
Modding a cheap 240v/60hz to 115v/400hz
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schmitt trigger:
Over 30 years ago, we required to operate an electrodynamic shaker, which was purchased at a flea market without its controller.
We used an old McIntosh MC275 vacuum tube amplifier, with its two channels fed with inverted polarity sinewave signals from a simple function generator as the power driver.

It worked correctly, but as it was operating at open loop control, we had to monitor it closely to prevent overdriving the shaker.

If it worked with an ultra-inefficient class B vacuum tube amp, I would also recommend as a quick solution, a class D audio amp with a step up transformer.

I hope no auidiophile is watching this thread...............
bdunham7:

--- Quote from: Yansi on June 09, 2020, 03:40:54 pm ---
--- Quote from: bdunham7 on June 09, 2020, 01:49:12 pm ---Converting them may be far simpler than rigging up a 400Hz supply.

--- End quote ---

I very strongly doubt that, unless they are some very very simple instruments. Especially, when the OP can't help himself with obtaining 115V 400Hz in the first place, modding any kind of avionics is I'd say outta question. I think there are many options to skin the cat here and most of them are appropriate and easy solutions (unlike some).  Just see back above.

--- End quote ---

The instruments don't need to be simple, just the power supply.  I'm guessing that they have a small transformer, a bridge rectifier, a filter cap and maybe a regulator.  Remove the transformer and rectifiers, run two wires out and supply it with 28 VDC.  Why would avionics be so special?
themadhippy:
Go old skool and build a rotary convertor,bog standard 240v motor driving a 115v 400hz genny,for 3 quid i'd be tempted to try using this motor as the genny
 https://mullard.org/products/motor-115v-400hz
Emo:
Are you sure you don't need three phase supply?
I did build a small 3 phase 400Hz power supply to feed an artificial horizon. Just a few watts with three channel audio amplifier like setup and RC phase shifts between the inputs. Not sure though if the three phase was also needed for the slave instruments like compass etc.

Eric
georges shed:

--- Quote from: themadhippy on June 09, 2020, 05:29:02 pm ---Go old skool and build a rotary convertor,bog standard 240v motor driving a 115v 400hz genny,for 3 quid i'd be tempted to try using this motor as the genny
 https://mullard.org/products/motor-115v-400hz

--- End quote ---

Good find! bought it...
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