DIY bulk eraser

[microx]

I like analog tape and all the nice old machines etc. I had no bulk eraser so I decided to make one. I took the mains tranny from a scrap 750 watt microwave oven and cut off the high voltage winding straight through the laminations leaving just the primary, in my case 230v.
This leaves an erasing face, but you cant just connect the coil to the main supply as the coil does not behave in the same way as before. I used a Variac and found that 30v gave a current of 4.5amps and the coil did not overheat. Fixed it to a board and included a pin to mount the tape reel on and two revolutions totally erased a spool of tape.
If you do this using a 120v tranny the I guess you will need more like 15v at 9amps.
Steve

 

[tardishead]

thats bloody cool mate! can you take a pic for me.
thats true DIY for you. I wish I had a bulk eraser aswell. sounds a bit scary though

 

[amorris]

nice! could use one myself. how did you cut through the tranny? a picture of the tranny would be most enlightening. 2 revolutions seems like a pretty strong magnetic field. are you talking about 2 inch tape? or 1/4inch? did the tape heat up alot?
rock on!

 

[turtle]

thats awesome, must go by thrift store to buy a microwave...........

 

[BYacey]

I made one from a 600W transformer core. I disassebled the laminations and re-asembled them with just the "E" parts of the laminations all oriented the same way. Previously the "E" and "I" parts alternated back and forth. (If you take one apart this will make more sense.) I also removed the secondary windings, and put a big oil filled capacitor in series to limit the current to a reasonable amount. Current was around 10A @120V , but I don't remember the capacitor value. The laminations have to be bolted back together tightly; If you don't the first time you power this up it'll scare the hell out of you with the buzzing and rattling noise. See my Avatar for more details.

 

[microx]

Yeah, I could not use the laminations trick as the tranny was welded so I clamped it in a bandsaw and cut right through it.
I also got from the scrap microwave the little gismo that rotates the plate to cook the food evenly. It turns at about 5rpm, so now the tape reel is driven round automatically. It only need a whiff of AC current to make it work so I wired across the coil. Driven from the variac it starts to turn as soon as the coil is energised. The whole thing works great.
Steve