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Old 21st Nov 2017, 1:11 pm   #11
ricard
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Join Date: Mar 2006
Location: Lund, Sweden
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Default Re: Marconiphone Reel to Reel 4218

There used to be various liquids which would act as 'magnetic developers' so that the actual track layout could be seen. I've never seen one of these myself, apparently they were some form of fine iron powder suspended in some form of solution, so that the iron powder orients itself according to the magnetism on the tape. Tandberg mentions the brand name 'Magna-See' in their service manuals.

I believe Scotch also had a device for observing tracks, essentially it looked like a looking glass, physically it was made up of a small circular container with a thin membrane on one side, the contained filled with fine iron filings, with the same principle of orienting themselves according to the magnetism when placed on magnetic tape.

Sorry to go to lengths for these now obsolete and most likely unobtainable devices, but this sounded like a clear case for which they would have been useful.

(On this subject I once bought a bottle of magnetite powder, intending to do some experiments; I remember mixing it with alcohol to see if that would be useful but couldn't get any useful pattern from the tape, instead the magnetite simply lumped up and didn't do anything. Perhaps a different carrier fluid would have been more successful).
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