Tape that won't record!

[Tractorfan]

Hi,
Here's an odd one.
A while back I was attempting to repair a Grundig TK149 and was using a 3" reel of tape for test recording. Having failed to resolve the problem, I put the Grundig to one side until another time, and the tape lay on the shelf.
Fast forward to yesterday evening when I used the same reel of tape to check my Philips N4418 before recording an important programme, only to find that it couldn't erase or record on that tape. Thinking that the machine had gone faulty at the crucial moment, I tried another 3" reel cut from the same 7" reel, and that one worked perfectly.
So. It appears possible that a faulty tape recorder (in this case the Grundig) can do 'something' to a tape to prevent it being re-used. But what? That is the question. Probably something obvious that I can't see.
Cheers, Pete.

[Tim]

It's not threaded on with the backing towards the heads is it?

[Tractorfan]

Hi,
No, Tim, definitely shiny side out! I'll try it again on another deck and see what happens.
Cheers, Pete.

[mickyfinn]

Some tapes are shiny side in.
Mick

[joebog1]

Only "tapes" I know of that are shiny side in, are carts for making add's
AND some sound stuff like Echolettes that have a large number of heads and actually "pull" the tape out of a cartridge.

Joe

[Phil G4SPZ]

Whilst searching through a batch of second-hand tapes looking for any worth saving for re-use, I came across one that was impossible to record on. Anything I recorded on it played back so quietly that it was unusable. I put it down to either loss or deterioration of the oxide coating. None of the old tapes proved to be any good; the comparison with new BASF LH was astounding.

Short of abrading the oxide away, I can't imagine that any tape recorder could do this to a tape. I'd suspect faulty manufacturing and that the tape had been binned as scrap, only to be offered for sale by some unscrupulous third party. Perhaps part of your larger reel was faulty and the rest OK?

It certainly is a strange one! You could try running your known good 3" reel through the TK149 again and see what happens to it...

[saxmaniac]

I have had this with certain tapes and it's nothing to do with the recorder A tape that plays back old recordings fine will not record over that with a new recording. It seems to be mainly with rubbish makes like Concertape and I have never understood why as the tape is not shedding oxide or sticky, it just doesn't record. If you try with a quality make of tape this problem doesn't arise (I think )

[ricard]

I once pulled the tape out of a DC600 cartridge, which is a format used to store computer data on (600 feet of tape storing 60 MB of data), to see what it was like. The tape is quarter inch and quite thin and completely black in color. Physically it works on an ordinary audio recorder, but when trying to record on the result was very quiet with no treble. Apparently the tape formulation used in this type of data cartridge is very different from what is used for audio (higher coercivity?).

[vidjoman]

There were several make of tape that had a matt coating applied to the back of the tape to improve spooling during high speed wind/rewind functions. They will be more shiny on the oxide side. A close look will often show the oxide side to have slight longitudinal scratches caused by guide or head wear. I've had tapes with known recordings on that have failed to playback after many years (30 or more) even though tapes stored with them were good.

[mickyfinn]

BASF super ferro LH for one I know as I use it.Gloss brown on the head side and matt black on the outer.
Mick

[Radio Wrangler]

I have some Agfa PEM368? with mat black cack coating... much matt-er than the oxide side.
I also have some tape with blue matt back coating... for some reason I think it is Zonal.

High coercivity tape with fine domains for max data density and endurance will be difficult to record on. It has a big hysteresis loop and needs enough applied field to drive it into saturation or it retains almost nothing.

Have you tried a bulk eraser? They're a good bit stronger than normal erase heads.

David

[brenellic2000]

I've had a couple of EMI 7" tapes, many years ago, which recorded/played back perfectly on one channel (mono top, left to right) but was quite muted on the second channel when flipped over as if the oxide was orientated for one direction only. I gave up in the end as bulk erasing didn't seem to make much difference. I guess it must have been a faulty oxide batch....

I can understand a matt carbon-backed tape being muted if back to front but doubt there would be a significant drop if glossy backed tape was so reversed.

[julie_m]

I suppose it's not utterly beyond the bounds of possibility that the bias signal on the machine that recorded the tape was too strong for the second machine to erase.

So now the question is, is oscillator #1 too strong, is oscillator #2 too weak, or is it weirdy tape? Not everything 6.3 mm. wide is suitable for home audio recording ...

[unitaudio]

When I was a kid I used to experiment with Dad's Fidelity Braemar (3.75" per second, quarter track mono) and one day I made a recording with the tape accidentally the wrong way round with the backing side to the heads. It recorded so well I didn't even notice for about a month! When I realised what I'd done I decided to leave it as it was because it sounded fine (at least by the standards of that machine which never had great top response whichever way the tape was put in!) and it's a pity I can't remember what make of tape it was.

I tried the same trick again on purpose with an Agfa tape but it hardly recorded at all. This had me scratching my head a bit at the time although now of course I know oxide formulations and backing tape vary widely.

Regards,
Paul

[Ted Kendall]

The fundamental property with top loss on tape the wrong way round is the thickness of the tape. Spacing loss in dB is given by 56 times the spacing divded by the recorded wavelength. So you can see that, firstly, it doesn't take a lot of spacing to cause a large drop in output and secondly that it will be worse at high frequencies. I'll leave you to do the sums, given that the thickness of triple play is about 18 microns and that of matt backed standard play up to 56 microns.

Given the tens of thousnads of batches of brew which went into magnetic tape over the years, it's hardly surprising that the odd reel won't behave - although the usual problem is lack of full erasure rather than failure to record at all.

[ben]

I have a really old (40s-early 50s) Anorgana Genoton tape which looks identical on both sides. Very dull and barely records.

Thinking about it, I once had a similar situation to the OP with a 1980s Toshiba Type I (FE) cassette. It would hardly erase and recorded very low. I imagined there was some deterioration on the tape surface, possibly due to bad storage, that impeded the head contact dramatically but I never pursued it.

[Ted Kendall]

Originally Posted by ben

I have a really old (40s-early 50s) Anorgana Genoton tape which looks identical on both sides. Very dull and barely records.

That's because it is identical on both sides. This sounds like the homogenous "G" tape which Abbey Road used for a time in the early 1950s when there were quality problems with Emitape. It is a brew with the oxide mixed into the plastic, which is then simply extruded rolled and stretched as normal tape. Actually works pretty well at 30ips full track.

[Lloyd 1985]

I remember when I was a kid, I bought some blank audio cassettes from a shop that sold really cheap stuff (Brierley's in Daventry!), I tried to record on them, and when played back it was really quiet, and fading in and out. I also found if I turned up the volume on a blank one I could hear some really quiet heavily faded music! I took them back and they gave me a new pack of tapes, but they were just as useless. Got my 50p back though! The tapes were branded 'Waltham'.

Regards,
Lloyd

[MeerKat]

I remember them, they were the pits! I think I even threw them away, that was hard for me!

Regards,
Andrew