EMT 140 Plate Driver Magnet

[kmozart]

Hi,

I just picked up two EMT 140 Plates, one mono and one stereo, in very bad shape with hope to rebuild them. I basically have two frames, one metal plate, two dampeners and two cases. amps and pickups/ drivers are unusable. Motors for timing are bad, maybe possible to rebuild. Electronics for the motors is in bad shape, maybe also possible rebuilt?!?!
Magnets are missing.

To begin, I hope to get one stereo working.

I'll clean them up nicely and put together the mechanics.

Where should I start looking for the electronics?
Anybody makes suitable amp, preamps, pickups, drivers,...

What are the options nowadays for a project like this?

I did the subject like this as it seems that magnet is impossible to be found.

 

[radardoug]

You can build your own electronics. You need a small (25 watt) speaker amplifier to drive the coil, and a couple of pickup amplifiers.
I recently refurbed a 140 by building amplifiers.
But I would suggest you build a small amplifier into the space where the pickups are, rather than using the long EMT cables. Use a TL071 or similar fet amplifier, use 2.2M as the bias resistor from + input to ground. Connect the transducer straight in there. Run the TL071 at about 30 dB gain.
With the motor, the suppression caps on the relay contacts will have gone leaky. Remove them. Put diodes on the relays rather than caps on the coil side.
For the coil driver, try and find a speaker repair shop. The gap in the EMT magnet is oversize to allow adjustment. If you find a good speaker repair shop they will have a magnetiser. You need to use a suitable speaker chassis, get it demagged, turn out the gap wider, and then remag it. All possible to do.

 

[kmozart]

Thanks radardoug!
Good advise!
I'll try to restore it with original parts, but if impossible to find, (or can not afford) I'll go DIY route.

Any particular speaker comes to mind? Any link to it?
Thanks,

 

[radardoug]

No particular speaker, that's why you need to find a speaker repair shop, they will have heaps to choose from and lots of technical knowledge. Another way to do it would be to machine up the appropriate shape in steel, and wrap a coil round it, and apply d.c. to it continuously, like the old electrodynamic speakers.