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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 15th Feb 2018, 6:26 pm   #1
red16v
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Default Some personal experiences on transferring old tapes.

It was in the early 1970’s that I became the proud owner of an Akai tape deck and I embarked on taping from the radio.

Fast forward 40+ years and my mind turned to transferring those tapes to a modern medium, for my own pleasure and hopefully for any curious and interested people. I began to read on the internet how best to go about this - Would the machine still work? Would the tapes play? I read about long term tape storage conditions and how storage in the loft was just about the worst possible scenario. No prizes for guessing where my tapes had been stored for 40+ years together with the recorder. I read about baking tapes, lubricating tapes with all sorts of magic ‘stuff’, how to get from my analogue tape deck to my digital iMac.

So, with some trepidation out came the deck and all those tapes. I spent my entire career as a professional electronics engineer and I should have known better, I did know better, but nonetheless I plugged the deck into the mains and simply switched it on.

It powered up, no smoke so the first signs were good! I left it for an hour or so to see if anything developed but nothing did so a good start. I bought an Behringer ADC, searched around in my box of old bits and pieces and found suitable DIN>RCA lead and plugged it all up, loaded a tape and pressed play. I got audio on my iMac! - good quality audio too, I was expecting to get hum but nothing at all apart from wide band background electronic background noise and of course tape hiss when the tapes were playing.

I played a mixture of tapes, some originally recorded at 7.5 ips and many recorded at 1/7/8 ips. The higher speeds tapes were just as good as the day I recorded them - remarkable! The slower speed tapes were obviously of lesser quality but of course they were in the first place over 40 years ago. What I did notice was quite a variation of playback audio level and the ‘end to end’ audio gain through the Behringer cannot be controlled via the iMac. So, I bit the bullet and bough a compact Zenyx audio mixer to be able to adjust the audio levels between the deck output and the Behringer. This turned out to be a very wise, inexpensive investment.

But as the project progressed so I ran into the problems that have been well documented across the internet.

Tape shedding oxide. Yes I had that. I had read abut baking the tapes and the various home brew methods some have employed. I bit that bullet again and put a tape I knew to be dispensable in the fan oven at 60 DegC for 4 hours to experiment. I let the tape cool down and I tried it the next day. Didn’t seem to make jot of difference. Still shedding oxide, sometimes shedding the backing too! I thought I’d simply press on and do the transfers anyway but making sure I recorded the material in one go so as not to stress the tapes any more than necessary. I idly watched the tapes as they came off the supply reel, over the roller and guides , past the heads, through the capstan etc onto the take up spool. Lots of missing and shedding oxide. But here’s the thing - imagine you are eating a bowl of muesli, chew it right up and then hold a piece of audio tape about a metre from your mouth then blow that muesli over the tape! Imagine what that will look like splattered over the tape - big bits, little bits, oblong bits all over the tape. Now imagine those lumps on the tape are not muesli - but that they are instead holes in the oxide, utterly completely missing oxide in a random, multisided pattern. That’s what my tapes were like in places. I watched those tapes pass over the playback heads. Nothing happened to the audio output! It was as though the oxide was still on the tape. Hard to imagine I know. Of course if the oxide was missing in a complete chunk across the whole width of the tape then of course the audio dropped out for the duration, but with lumps and bits missing even in a confined and dense area of the tape it seems not to care in the world. I can’t quite get my head round that and I am still thinking about it, I am trying to develop a theory in my mind that the magnetic field emanating from the tape is inducing a (replay) field in the whole width of the head poles as it crosses over the heads. In other words the playback magnetic filed is not a narrow, sharply defined field, but a much wider field that can - to some extent- mask missing parts of the replay magnetic field containing useful audio provided the length of the missing audio is not physically longer than the shoulders of the replay heads that the tape is passing over. probably not making a lot of sense there but it is clear in my mind - no matter, the audio was recovered!

Then I had the squealing as some of the low speed tapes (1.7/8 ips) were churning their way across the tape path. Was it the roller guide? Was it the fixed guides? Was it as the tapes passed over the replay heads? Was it the tension arms in the supply and take-up path? It was all of them at one time or another. I realised I was suffering from sticky tape syndrome but the tape baking didn’t help me at all. I’d seen that video on youtube of that chap spooling his tapes from end to end while wrapping the spooling tape in a cotton swab soaked in some sort of magic silicone liquid. I thought I’d have go at that since I had some liquid silicon car polish in the garage. Word of warning here. Don’t try this in your living room because as the tapes are spooling from one reel to the other and being swabbed in silicon car polish then naturally Nature’s centrifugal forces are going to want to fling that polish off the tapes and onto your living room wall paper. So, if you want to try this at home do it outside if you can or do as I did which was to envelop the tape deck in a cocoon of old newspapers to soak up the damage so as to speak.

Did it work. Not really sure, I think there was some improvement but not a lot. What I did find very useful was that if I came across a piece of tape that was very ‘squeaky’ I would stop transferring the tape, rewind it, start of the transfer again, but this time i would hold a cotton bud soaked in the liquid car polish on the front surface of the tope (yes the oxide side) as it came off the supply reel. That seemed to work 50% of the time. Some of you will be holding your hands up in horror at the thought of all that silicon ‘goop’ jamming up the heads - jamming up the pole gap. I figured silicon is an insulator so if its filling up the head gap ‘so what’ it’s an insulator and it isn’t going to short anything electrical or any magnetic fields.

What about the other 50% I hear you say. Well I eventually found a solution for that too. Plumbers PTFE tape - you remember, that old very thin, very slippery tape plumbers use to seal the threads on a threaded joint. I put it everywhere except across the replay heads. I wrapped it around the tension arms, roller guide, fixed guides, the biggest culprit was the master erase head and so I simply wrapped the PTFE tape around it several times - sure did stop that squealing! But it did tend to get rubbed through reasonably quickly which isn’t all that surprising when you consider the oxide will be acting like a ‘rasp file’ across the PTFE tape. So checking and replenishing often was important.

Any other tips? If the supply reel tension arm tended to squeal and if the tape was not too bad (not sticking as it came off the supply reel which would lead to ‘judder’ on the tape as it came off the supply reel which would translate to ‘judder’ on the replay audio as it passed over the replay head further downstream) then I held the tension arm back from touching the tape with an elastic band. Sometimes I completely bypassed the take-up reel tension arm, the tape seemed to spool nicely onto the take up reel anyway and please remember I was only going to be playing the tape once.

I was using the Audacity audio editing software - so here’s another tip. I found the slower the original replay speed of the tape the more likely you were to get problems. Tapes with higher replay speeds tended to be completely trouble free. Here’s the tip - play the tape back at double speed and ingest it onto the Audacity software. Then use Audacity to halve the speed! Does it really work I hear you say? I experimented with several tapes and I couldn’t tell any difference on the final output. What about all those high frequencies I hear you say - you’ll lose them for a start off! Well, My thinking was if I was replaying a tape originally recorded at 1.7/8 ips there wasn’t much HF on the recording to start off with so I’m hardly going to be losing anything by replaying the tape back at double speed.

Biggest tip of all - the obvious, keep demagnetising the heads, keeping cleaning the heads with alcohol to get rid of the inevitable silicon goop, keep the pinch wheel clean with warm soapy water only.

The end result. Many hours of recordings, on different manufacturer’s tapes, recorded at different speeds, stored in the loft for 40+years successfully transferred.


To be serious though, this was a labour of love and if any of this practical feedback helps anyone here then I am doubly pleased.

Last edited by red16v; 15th Feb 2018 at 6:33 pm.
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Old 15th Feb 2018, 11:47 pm   #2
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Default Re: Some personal experiences on transferring old tapes.

A very interesting post!! I suspect I may have similar issues playing back open reel video tapes I recorded in the '80's: I've yet to investigate.
Out of interest, the standard PTFE tape is very thin. You can get a very much thicker version which is for natural gas jointing. It comes in a yellow case. I wonder if that would be more long lasting?

40 year old tapes stored in a loft can still be recovered 40 years later. What are the chances of your digital files being readable after 10 years let alone 40? They will need regularly updating to new readable files over that period. Same applies to digital photos- its a very transitory medium! Analogue has some fundamental advantages.

I read in a technical journal that this has become a real problem for the film industry where all modern films are made digitally. The only long term method of storage they have come up with is to archive them onto black and white film stock!! The film is split into three primary colours and stored separately I believe.

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Old 16th Feb 2018, 10:38 am   #3
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Default Re: Some personal experiences on transferring old tapes.

With regards to the ptfe tape, I guess the only restriction on thickness would be that it has to be quite flexible in order to be able to wrap it around some guide posts that have a small diameter, I didn't find the 'original' white tape to be any sort of problem. I put 3 or 4 horizontal strips over the upstream erase heads. Can I post pictures here? I will if I am able if it helps anyone.

Digital files, I have saved all the material to wav files and I imagine they will supported for quite some time. If not, I would fully expect any replacement to be compatible with wav files as they are so very widespread - or some form of file conversion.

35mm film, yes, that process has been round for quite some time. One of my own personal favourite films was stored in that manner by the director as he was well aware of the long term storage problems - 'The Umberellas of Cherbourg' to give it it's English title, by Jacques Demy.

The other thing I don't mention in my original post was occasional 'cracking' (not crackling) on the audio. I really couldn't make this out and in the end I decided it was possibly down to a build up of static on the tape - this was before I started to use the ptfe tape.

I gave it some thought and came to the conclusion that maybe the combination of a dry atmosphere and dry plastic tape backing scraping across fixed guides etc was maybe causing a static build up on the tape which then (maybe) discharged occasionally causing the 'crack'. How to deal with it? Well I took what I thought was the easy route, I found an RCA>RCA lead, plugged one end into the tape deck then very carefully positioned the other end so that the outer shell was just pressing into the rear of the tape as it left the supply reel but before it reached the erase stack. I had to hold the lead carefully in place with an elastic band!

There will be horrified faces now thinking: My word, now you have distorted that nice flat oxide surface and you will get all sorts of problems with head/tape contact, tape rippling etc, etc. Tape is a very flexible physical medium and provided you keep your mitts off it, and don't smoke over it you will have to really have to go some to physically damage it permanently. You can happily bend it into all sorts of shapes and it will recover. I used to work with quad VTR machines and with those the tape was deliberately distorted from a flat profile into a 90 degree curve and back again. if you got some 2" tape and twisted a few lengths of it together you could use it as an emergency tow rope for your car!!

Last edited by red16v; 16th Feb 2018 at 10:44 am.
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Old 16th Feb 2018, 12:25 pm   #4
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Default Re: Some personal experiences on transferring old tapes.

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Originally Posted by red16v View Post
Tape shedding oxide. Yes I had that. I had read abut baking the tapes and the various home brew methods some have employed. I bit that bullet again and put a tape I knew to be dispensable in the fan oven at 60 DegC for 4 hours to experiment. I let the tape cool down and I tried it the next day. Didn’t seem to make jot of difference. Still shedding oxide, sometimes shedding the backing too!

Hi red, some sticky tapes respond to baking and others dont. Some should never be baked. If they do respond to baking it must not be in a gas powered oven because it produces moisture which we're trying to remove. Badly affected tapes with a lot of absorbed moisture might need a lot more than 4 hours to dry them out, sometimes 24 hours or more.

If the tape starts shedding the oxide that's it. The signal at those points where the oxide has come off may as well be lost for good. If you're lucky there's no signal recorded at those parts of the tape, or there's still some signal either side of where the oxide has come away.

The car polish treatment is promoted by a guy on the web but as far as I know it's not a treatment recommended by anyone doing this work professionally such as for record and film company archives.

There are two less invasive techniques for what some call "soft binder syndrome". One is "cold play" where you literally play the tapes back on a machine sitting in a refrigerator. The other is using isopropyl alcohol or "D5" as a short term lubricant on the tape before it evaporates.

A fair bit of study has gone into this area and more information keeps coming in from people doing this work.

Here's a good source of information including a list of affected tapes:

http://richardhess.com/notes/formats...grading-tapes/
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Old 16th Feb 2018, 1:14 pm   #5
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Default Re: Some personal experiences on transferring old tapes.

Last year I resurrected an old tape recorder to play old tapes that I had recorded in the 1960's onto computer.
As I could only get the machine to work satisfactorily at 7½ips I too using Audacity was able to listen to 3¾ips recordings. Fortunately I never recorded much at any lower speed.

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Old 16th Feb 2018, 8:05 pm   #6
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Default Re: Some personal experiences on transferring old tapes.

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Here's a good source of information including a list of affected tapes:

http://richardhess.com/notes/formats...grading-tapes/
Thanks for that link, it was one of the ones I had seen whilst I was researching how to go about this before starting my project.

I did try the isoprop trick but it did not work at all for me, although I always used it to clean the heads and guides. I only washed the pinchwheel in warm soapy water.

The oxide shedding/replay situation is very unclear to me. Imagine a piece of quarter inch tape with a round hole about 1/8th diameter of missing oxide in the middle of it. I play the tape and the audio is there! Why isn’t it missing? Ah, you might say, you have a dual channel stereo machine and perhaps by chance the oxide will affect the other two stereo tracks? Nope, just the same on those tracks!

I am convinced it must be to do with the relationship between the physical length of the missing oxide and the width of the ‘shoulders’ of the replay head. The magnetic field recorded on the tape is not the sole result of the field just around the audio head gap, it must also be ‘impressed’ onto the tape across the entire shoulders of the recording head. I would imagine there might be a reduction in the audio level - but not a complete loss of audio. My practical results would seem to confirm this and this was true even with tapes running at 1.7/8 ips, tapes running at 7.5 ips really weren’t bothered by it at all in the least. Very curious really as it would seem to defy scientific analysis?

Edited to add. Running the tape at high speed through a swab of car polish was not too successful I have to say, but, holding a cotton bud soaked in silicone car polish against the oxide in places where it was really screeching worked well. These were short sections I’m pleased to report and again only really on tapes playing back at low speed.

Last edited by red16v; 16th Feb 2018 at 8:13 pm.
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Old 17th Feb 2018, 3:42 am   #7
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The oxide shedding/replay situation is very unclear to me. Imagine a piece of quarter inch tape with a round hole about 1/8th diameter of missing oxide in the middle of it. I play the tape and the audio is there! Why isn’t it missing? Ah, you might say, you have a dual channel stereo machine and perhaps by chance the oxide will affect the other two stereo tracks? Nope, just the same on those tracks!
It doesnt have to be a complete loss of the magnetic coating. "dropouts" have always been an issue with magnetic tape, whether for video, audio or data. A small speck of dirt or a clump of oxide particles momentarily lifting the tape slightly off the head can be enough.

Part of the tape manufacturing process was "calendering" which involved polishing the surface of the new tape to make it as smooth and even as possible as it rides over the tape heads. Even on brand new tape, manufacturers gave a specification of "uniformity" at different frequencies.

You mentioned video recording. A glitch free picture probably wasnt possible without a "dropout compensator" which substituted momentary losses of signal in one scan line, with the signal from the previous scan line.
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Old 17th Feb 2018, 11:09 am   #8
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Default Re: Some personal experiences on transferring old tapes.

Because of the logarithmic volume response of human hearing, a missing chunk of oxide that's noticeable to the eye may not be noticeable to the ear. If half the oxide is missing from a track at one point, that'll amount to a 3dB loss of audio output power, a drop which is barely noticeable to ears.
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Old 17th Feb 2018, 3:54 pm   #9
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Yes a big difference between half the width of the track missing, and all of it missing. But I got the impression that "lots of missing and shedding oxide" would include "holes" at least as wide as the complete track especially when it's only quarter track.
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Old 17th Feb 2018, 8:16 pm   #10
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Default Re: Some personal experiences on transferring old tapes.

Thanks for the write - up, great to see a result after all that toil.
In the course of making my archive of found sounds, I have come across pretty much everything in terms of tape deterioration. I have seen water and mould damaged tapes, deformed tapes, tapes with adhesive from sellotape gumming up the layers, and tapes that were worn so much in a language lab that there was little oxide remaining on parts of them.

I have had to use hot and cold treatments, and modify transports. As you discovered, the fewer contact surfaces the better, in the case of SSS tapes. Last mildly sticky case I had, I used the backing sheet of a page of adhesive labels around parts of the tape path to reduce friction.

The worst case actually turned out to be a fairly recent acquisition, some tapes that had almost certainly spend a few decades in a loft. These had adjacent layers tightly stuck together, unspooling was like using a reel of sellotape. Large chunks of oxide were stuck on the back of the layer below. After trying various experiments with heat and cold I found that the speed and angle with which the tapes were unwound were critical factors. I am still in the middle of the salvaging process but it is amazing how much abuse a tape can have and still be listenable. So far in three and a half decades, I have never had to give up on any tape. Unlike digital, analogue can usually be recovered. I say persevere, and keep experimenting. In addition, it pays to have several recorders with different tape paths and handling (braking, backtension, spooling) properties. Some are so gentle you'd never imagine a tape breaking on them; others can be pretty brutal!
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Old 24th Feb 2018, 10:35 am   #11
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Default Re: Some personal experiences on transferring old tapes.

sue butcher, TIMTAPE - sorry not to have responded earlier.

For clarity 'yes' I am referring to missing oxide that is at least half the width of the individual tape so crossing the height of the entire track(s).

What I personally think is important to think about, is that it is the length of the 'drop out' rather than its height (hope that makes sense) since I am speculating that the loss of signal caused directly by the missing oxide is in fact compensated for by the remaining signal either side of the missing oxide still being sufficiently strong enough to induce a signal into the shoulders of the head. I think suebutchers point about relative drops in audio levels not being noticeable to the human ear is very pertinent here.

Is there any evidence to support this? I tried looking at the audio waveform at a dropout point on Audacity to see if there was any reduction - I could not readily see any but it was very difficult to pin point an exact point and the material was music not a steady tone. So not helpful I'm afraid.

I think back to my days in quad VT, the head layout patterns being very different to audio but the principles being the same - trying to induce a magnetic field into the tape and recover as much of it as you could, and, we were recording a narrow band FM signal not an amplitude modulated one. One of the very useful monitoring instruments we had was a meter displaying the RF level coming off the tape. If you changed a head wheel panel for a new one (the panel containing the heads) and recorded and played back a test signal the level would be a certain amount. As the head wheel panel gained use over the weeks there would be a distinct increase in the amount of RF signal recovered from the tape. It would not be unusual at all for the signal level to double in amplitude over the course of say 500 hours. We put this down to the fact that as the tip of the head itself was wearing down so more of the shoulders of the head came into contact with the tape's surface and so more of the recorded magnetic field was being induced into the complete head and hence more output. Perhaps you can see why I was trying to stretch the theory a bit by seeing if there was any sort of analogy with audio recording?

Please don't think you have to respond or spend any time thinking about it as 'it is what it is' and I was more than happy with the end results. Just a bit of fun thinking about it. Unfortunately I boxed the machine back up and put it away as soon as I finished the transfers otherwise I would happily take some photos of the kind of of dropouts I was experiencing. My wife would go crackers if I unboxed it again so soon!

TIMTAPE, you mentioned video tape drop out compensators. In the early days at the RF dropout point the machines inserted a length of black to cover the loss of perceived video, some inserted grey. This was then thought to be less than satisfactory and so they developed the technique to replace the missing video with video from a previous line as you mentioned (taking v axis switching into account of course). A long long time ago!

One further distraction perhaps of interest again with regard to quad recording. If you were about to do a prestige recording you never used a new tape as you didn't know it's condition. You always tried to use tape that had perhaps passed under the heads half a dozen times so that it was nicely polished and any surface debris was likely to have been swept away. The oxide formulation was, I believe, applied such that it was optimised for recording across the width of the tape rather along it since of course that is how quad recording worked - at least that is what the salesmen said. We sometimes mused about using the 2" tape supplied for use on the 24 track audio machines as it was a lot cheaper but we were told that the formulation on that was obviously optimised from longitudinal recording. Despite chatting about, I don't know anyone who actually tried it! Perhaps it was a different thickness too!
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Old 24th Feb 2018, 1:45 pm   #12
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I've done a lot of transfers from tape to digital and have lost count of the times I've both heard dropouts and seen the same dropouts very clearly on the DAW screen. I also have off air recordings of professional videotaped programs where the dropouts were sometimes audibly horrendous. Most of the time they didnt seem too bad though.

There was always something called "fringing effect" where low frequencies are picked up by the head gap even when they fall either too high or too low of the actual gap. The higher the frequencies the more the effect disappears.

Re videotapes which had better RF output after running the tape through a few times, that's definitely true. Ray Dolby as young man worked in the design and development team at Ampex on the first 2" VTR. He noticed this and put it down to the polishing effect on the tape that you mention, making for more intimate tape to head contact. It can also apply to tape heads if they are not quite polished smooth enough when installed and the tape does the final polishing. I'm not sure though about the idea that the head tip was not covering the full width. The tips should have been be lapped to be perfectly perpendicular to the tape right across the gaps, and that applies to tape heads today as much as then.

I believe 2" video tape got a hard life what with those rapidly spinning heads and the tips - which also had a very hard life -which buried themselves into the tape layer at great speed.

Thanks for the info about the use of grey or black to cover the dropout before proper dropout compensators were invented. I guess grey would have been better, being less noticeable overall.

I've always been amazed at the feat of designing and making those first huge Ampex video tape machines back in the 1950's and then colour only a couple of years later. At their first demonstration to TV industry executives the machines' instant replay apparently caused a sensation.

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