My latest purchase - OSMABET instant tape eraser

[ToTo Man]

I don't really need one of these, but when I see something cool that's in such excellent and original condition I find it hard to resist.

This Osmabet 'Instant Bulk Tape Eraser' from 1959 is a particularly nice example, even the cardboard box looks almost like new with no evidence of damp or torn seams.

This the oldest electrical item I've ever bought, it appears to pre-date the UK 3-pin plug, though an adapter has been included. I'm not sure if this adapter would have come with the unit originally or if it was bought at a later date by a previous owner.

I'm rather nervous about plugging it in to test. The casing on the unit looks to be all plastic so presumably the risk of electric shock is minimal, but perhaps I'd be safer offering the tape up to the eraser rather than the other way round, so that I don't need to hold the unit in my hand?!

 

[Vinny]

I have something broadly similar, minus box. That was sold entirely as a head demagnetiser. Is is just a coil around a soft iron probe, so produces a 50Hz oscillating magnetic field.

The adapter will be reasonably "new". I haven't looked up when square pin became the norm, but back then it would have been 3 round pin, I am pretty sure.

I remember that sort of plug being normal on, of all things, aquarium air pumps, which were very similar in operation really - a coil that produced an oscillating field that caused oscillation of a permanent magnet attached to what were in effect, bellows.

One hell of a price - £1.36

The company got around quite a bit - loads of hits f you Google the name.

Vintage Osmabet PPT/1 Power Pack Transformer | eBay

Hybrid Audio Amplifier (r-type.org) (uses an Osmabet ransformer).

Also, post #76 -

Calling Reel-2-Reel Tape experts - TEAC A3440 15ips speed problems | Page 4 | pink fish media

 

[Werner]

Mine is much bigger.

I got it for small money, shipped from London to Belgium, all 30+ kg of it. Crazy.

It makes a racket to raise the dead, dimming the lights in the neighbourhood. It erases tapes well. Except metal.

https://picclick.it/Weircliffe-BTE-200HDS-Compact-Media-Degausser-Uncalibrated-302275171915.html

 

[Beobloke]

I have one of the Sony BE-9H models that is basically a hugely powerful magnet in a box, complete with its micro cassette adaptor!

 

[ToTo Man]

Well I threw caution to the wind and convinced my dad to try it today on a standard low-noise Maxell UR cassette tape. It's a fairly quiet unit in operation, it only gets loud when it's in direct contact with a tape. I was fully expecting this, but my dad wasn't, you should've seen his face when the cassette tape suddenly stuck to it and began rattling, - I wish I'd filmed it!

We did a few passes each side of the cassette and then I played the tape back in my Technics RS-B11W. There's no trace of the previous recording on the tape, so the eraser appears to do its job. There is however a faint, repetitive 'swooshing' noise on playback, and the noise floor of the now 'virgin' tape doesn't seem to be any quieter than if I simply erase the tape in the deck itself by recording silence. Maybe the playback head of the RS-B11W is just too noisy to reveal the difference?

 

[Darmok]

^^ You should read the instructions on how to use a head demagnetiser. some should be near the heads at an angle then you have draw it away in the directions explained in the manual.

 

[Werner]

There is however a faint, repetitive 'swooshing' noise on playback

That is due to insufficient uniformity of the erasure field as applied to the tape. In other words: it erased, but left its own imprint. Fine if you want to destroy a recording, not if you want to return a tape to virgin state.

and the noise floor of the now 'virgin' tape doesn't seem to be any quieter than if I simply erase the tape in the deck itself by recording silence. Maybe the playback head of the RS-B11W is just too noisy to reveal the difference?

Possibly. There should be 2-3dB difference between virgin/bulk-erased and AC-head-erased. The swooshing, however, clearly sits above the Technics' noise floor.


BTW, when I have to handle suspect/old electronics I use a variac for AC supply, slowly turning it up. There are cheap decent ones available these days.

 

[ToTo Man]

That is due to insufficient uniformity of the erasure field as applied to the tape. In other words: it erased, but left its own imprint. Fine if you want to destroy a recording, not if you want to return a tape to virgin state.



Possibly. There should be 2-3dB difference between virgin/bulk-erased and AC-head-erased. The swooshing, however, clearly sits above the Technics' noise floor.


BTW, when I have to handle suspect/old electronics I use a variac for AC supply, slowly turning it up. There are cheap decent ones available these days.

I was wrong in my earlier post, I've done more listening tests and the bulk-erased tape does have a quieter noise floor. When I record over it with the Technics the background hiss becomes louder, I'm not sure how many dBs louder, I'd need to capture it via my ADC and analyse in Audacity. Also, when I record over it, the repetitive 'swooshing' noise is no longer audible, this could be because the deck's erase head has successfully removed it, or the increased noise floor could be masking it.

If a deck's erase head is able to remove the swooshing noise, then presumably it's not a problem? I'd be using the bulk eraser to erase tapes that were originally recorded on my Technics so that I can use them as blanks for my Akai. Do you think it's better to use the bulk eraser even though it leaves its own imprint, or is it better to rely on the Akai's erase head to erase the Technics' recordings? Does the latter require the Technics and Akai heads to be in perfect alignment with each other?

 

[Martyn Miles]

The Talking Newspaper I worked for had a Weircliffe build eraser.
Nine cassettes at one go, if I remember correctly.
We sometimes used ex. Police cassettes ( Neal ) and the ex. policeman who read for us called it
‘The Watergate Machine.’

He explained why the Police used cassettes as they were very difficult to tamper with.
The NEAL recorders only had record and stop buttons.
They were also security sealed and had to be inspected regularly.
Presumably the Police use some sort of secure digital system now.

 

[Werner]

Under most conditions the heads are sufficiently aligned not to need a bulk eraser.

A BE is useful when you are in a hurry. It may also be useful for 'hard domains'. These are magnetic particles that get stuck after recording. No matter how often you re-record the tape, the original recording keeps surfacing.

 

[Barrymagrec]

The adapter will be reasonably "new". I haven't looked up when square pin became the norm, but back then it would have been 3 round pin, I am pretty sure.

I remember that sort of plug being normal on, of all things, aquarium air pumps, which were very similar in operation really - a coil that produced an oscillating field that caused oscillation of a permanent magnet attached to what were in effect, bellows.

One hell of a price - £1.36

I remember seeing advertisments for these in the 1960s.

BS1363 for square pin 13amp plugs / sockets came out in 1947 so predates the unit by a long time, of course many of the older installations using BS546 round pin plugs / sockets stayed in use into the seventies and beyond.

The Eraser would have been supplied without a plug as most appliances were in those days, there being a possibility of 7 different types (plus the bayonet lampholder)......

 

[Vinny]

of course many of the older installations using BS546 round pin plugs / sockets stayed in use into the seventies and beyond.

The house opposite sold a few months back. That was built well into the 50's, and the new owner has been doing lots of minor updating, general redecorating etc.. He had never seen round pin plug tops, so was amazed to find them around the house. The house had not been especially neglected, but successive owners had not changed at least some of the original sockets. My local has (or had when we were last there oh so many months back), plenty of round pin sockets - it is a brewery-owned house so electrical instalations are not the responsibility of the publican - Ben moaned like hell about having to change plugs around on things as he was unaware that (fused) round pin plugs are still sold.

 

[Barrymagrec]

Our house was built around 1935 and when we moved in in 1986 most of the original wiring had been replaced but there were still a couple of operational 2 pin 5 amp round pin sockets connected with the original lead sheathed cable - I disconnected them pretty smartish.

My parents first house, built in 1954 had 13 amp sockets from the off, brown, one per room.

 

[Vinny]

Our house was built around 1935 and when we moved in in 1986 most of the original wiring had been replaced but there were still a couple of operational 2 pin 5 amp round pin sockets connected with the original lead sheathed cable

LOL, yes, I remember all that. 1980's though - that was incredibly late for lead to still be in use.
My parents' place was built around 1900 and had been rewired with rubber when they bought it in the late 1940's. They had the place rewired with PVC and square pin in the late 60's/early 70's. I also remember the gas mantle light fittings that were never used to my knowledge. I also remember the long lengths of lead coming out of walls over the years when decorating was done. Those lengths of lead provided me with my home-made "shot" for my first fishing trips.

 

[Tony L]

If a deck's erase head is able to remove the swooshing noise, then presumably it's not a problem?

You’ll maybe find the decks ability to erase depends on the type of tape. I’ve noticed my mid-70s Akai 4000DB reel to reel struggles erasing some tapes that I assume are a later generation than it is. R2R tape isn’t labelled as clearly as to what it is, e.g. ferric, fe-cr, cr etc, and my 4000DB only has ‘low noise’ and ‘wide bandwidth’ as options, which to be honest mean nothing to me!

 

[cctaylor]

My wife's family home was wired by the landlord (the Crown Estates) in the 60s with one single socket per room. My MIL was so anxious about this new fangled electricity and so worried about overloading that no adapters were allowed. So to use the iron the telly was unplugged.

 

[ToTo Man]

You’ll maybe find the decks ability to erase depends on the type of tape. I’ve noticed my mid-70s Akai 4000DB reel to reel struggles erasing some tapes that I assume are a later generation than it is. R2R tape isn’t labelled as clearly as to what it is, e.g. ferric, fe-cr, cr etc, and my 4000DB only has ‘low noise’ and ‘wide bandwidth’ as options, which to be honest mean nothing to me!

I was thinking more about cassettes TBH, as since my Revox B77 was overhauled by Alan I haven't put old tape stock of unknown provenance anywhere near it. The amount of time it takes to thread a reel to find it records with drop outs and sheds oxide coating all over the tape path isn't worth the hassle IMV. The cassettes, on the other hand, are ones I bought new in the 90s/00s and have only been recorded on once, so I'm assuming I'll be able to reuse these if they erase ok. I did however record a lot of them on the hot side (+5dB peaks), I don't know if this makes erasure more difficult?