The Cheapskate's Cart Eraser
A cart eraser is shown on some of the original studio plans but was either never bought, or by 1990 was long since nicked by some thieving gyppo station manager. Mr Fitch didn't see fit to put an erase head on the recording cart machine and re-winding new cart tape into Aristocarts every time you record a dud is wasteful, so some form of cheap bulk eraser is called for.
Hmmm,... <surveys available junk in the area and eyes light upon two very large old transformers in the technical cupboard, once part of a linear power supply for a PDP-11 mini computer... thinks>
>-Cue Blue Peter theme tune (Mike Oldfeld version)
* First heft your two very large conventional iron stamping-type core transformers out of the technical cupboard and into your room, make a large pot of two-teabag tea and put on a Saturday afternoon gladiator type film, or black and white war movie or similar.
* Remove any bolts clamping the iron core stampings together.
* Now the tricky bit - you may need an adult to help you. Use a hammer and a flat bladed screwdriver, kitchen knife, and anything available to break the varnish on one of the outside stampings and try to separate it as much as possible from the others around the outside of the core. This done, the stamping will probably still be firmly attached via the section which goes through the core. Use persuasion, levering, poking, hammering, Mole grips etc. to wheedle the core section loose and pull out this first stamping, which will by now be quite badly mangled and discard it.
* Repeat this much more carefully with the other stampings until you have them all separated and chip off the rectagular "I" iron pieces from the "W" pieces.
* Put all the "W" pieces on top of each other the same way round and push them back into the core so that you end up with a three pole electromagnet. Bolt them back together but don't go mad tighentening them, remembering that the reason for having the stampings and varnish in the first place is to avoid conduction amoung them causing big eddy currents.
* Repeat with transformer 2, put gaffa tape across the top to stop bits of magnetic crud getting in and mount both on a lump of chipboard. Wire in series across the mains, moving upwards in plug-top fuse ratings until you get to one which doesn't blow. It's important to use two in series, as the inductance of the transformers is massively reduced by opening up the magnetic path to the air. Using just one will allow a too large current to flow and result in rapid heating of the winding. Always leave the secondary windings open.
Et Voila! You are now ready to erase jingle carts, cassettes, reel-to-reel tapes, your mate's cashpoint card, floppy disks with final year assignments on, etc.
Instructions for use
Plug the device into the mains and switch on. There will be a slight hum which is perfectly normal and shows that the device is operational.
Place the cart between the pole pieces and move it around with a circular motion. Maintain this circular motion while slowly lifting the cart away from the poles and finally well away.
Switch off. Some warming of the device when in repeated operation is expected.
Check for full erasure before recording, if the recorder has no erase head.