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The Neoprene Problem


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This page was originally written by , and I have updated it slightly to include new information.


The Neoprene Problem: Idler Wheel & Pinch Roller Decay

Anyone thinking of buying a Series 7 or later model should be aware that unless the idlers and pinch roller have been replaced it is likely to be affected by this problem.

The chemical decomposition of the 'rubber' idler wheels and pinch rollers is a serious fault that seems to have affected most Ferrograph tape recorders made from around 1970 up to the end of production in 1981; in other words, from Series 7 onwards. Because it is so widespread it has, very regretably, probably had a detrimental affect on the value and collectability of the Ferrograph make as a whole.

Although deterioration of idlers and pinch roller do not necessarily happen simultaneously, most owners of these decks first notice the problem when they find that the pinch roller has degraded into a sticky, or soap-like, consistency. Even if it will grip the tape to the capstan, bits of gooey pinch roller will pare off onto any tape run through the deck.

The same deterioration of the idler wheels usually first shows itself by a rumbling noise, especially at the highest tape speed. On inside inspection, the rubber compound will be found to be depositing itself on the capstan motor pulley and flywheel. At the very least this will be bad for wow and flutter, and at worst it may seize and damage the motor. In this state the deck - even though it may still run - is unusable.

However, do not discard decayed idlers or pinch rollers - the metal hubs may, as mentioned later, be recast with new rubber.

Why so much critical 'rubber'?

All Ferrograph tape decks - apart from the Studio 8 - rely on this rather antiquated (a 1940s design), relatively noisy, but nevertheless effective system of driving the capstan from a high speed motor by intermediate, or 'idler' wheels (early Ampex machines also used a rubber intermediate drive system). These wheels are fitted with a moulded, synthetic rubber tyre made of neoprene (generic name, polychloroprene), a normally very stable and durable compound.

The earlier Ferrographs used a brass pinch roller, with the resilient coating on the capstan itself; but the change in capstan design with the Series 7 involved a change to a neoprene-tyred pinch roller too (as is found on almost all other makes of tape deck).

These components cannot be simply substituted, as correct size, hardness, and accuracy of profile are critical to good speed stability, or wow and flutter.

Why only the later Ferrographs, and why are so many of them affected?

The idler wheels on pre-Series 7 Ferrographs rarely, if ever, seem to be affected by this trouble, being usually still resilient and working well, even after forty years or more. (Contrary to some opinion these items were not pure rubber on earlier Ferrographs - or certainly not from the late 1950s onwards: handbooks refer specifically to 'neoprene'.)

So the problem cannot be blamed on the choice of neoprene or its normal ageing even on the Series 7 the self-wrap reel brakes, which are also neoprene, never develop this trouble. The answer seems to be a specific manufacturing fault and, moreover, one that was allowed to go uncorrected for many years. This failure of quality control sounds very un-Ferrograph, but the cause seems to have been external.

Apart from the more basic items, like fasteners or, of course, electronic components and specialised products like panel meters, most of the parts in a Ferrograph recorder were made in-house at the South Shields factory - this includes the heads, and even the motors and transformers. One important job done by an external contractor was the casting of neoprene 'rubber' onto idler wheel and pinch roller metal hubs (or the capstan itself, in the case of older models). I do not know which firm did this work, nor if they still exist, but a chronic problem with the quality of the material they supplied seems to have started around the end of the 1960s.

For a long while I had assumed this had only emerged sometime in the 1980s, as a slow chemical change finally took effect. However, in July 2000 I received an e-mail from Sebastian Bertolini in Ardenno, Italy, which changed my perception of this. He told me: -

"...the problem of Ferrograph neoprene was already known in 1976. The Ferrograph dealer used to substitute all of the neoprene parts of the machines before selling them to customers, by a clone of those parts made here in Italy using good quality rubber (the machine I own has this clone mounted and it's still perfect after more than 20 years). The original neoprene [was] taken away from the metal part and substituted. The problem in the original mixture of rubber [was] found to be a poor quality of the vulcanization process that made the product very unstable."

So it seems this was well known by the mid seventies, but that the rubber contractors were not taken to task. Could Ferrograph have really been unaware of it? It seems unlikely, and it must be said that even if they were not directly responsible this is not excusable: because of this fault, many decks may have been prematurely scrapped, and unnecessary expense incurred in replacement parts even as far back as the 1970s.

Possible solutions.

How, then, do we deal with the problem now? The only answers are to either:-

  1. Use newly manufactured parts;
  2. cast new 'rubber' onto the metal hubs; or
  3. in the case of idlers only, use old ones from 1950s and 60s decks for Series/Logic 7s;

Unfortunately it is not currently possible to obtain rollers manufactured specifically for Ferrograph recorders. Until a few years ago newly manufactured parts were available from the now-defunct Ferrograph Spares and Service, a firm which was unconnected with the original Ferrograph (or NEAL Ferrograph) companies, but which was based in South Shields and benefited from the expertise of one or two ex-Ferrograph employees. They provided very good, newly made idlers and pinch rollers.

The tyres on these products, rather than neoprene, were polyurethane - a material with a bit less wear resistance, but likely to be much more durable in the long term than the original parts due to good chemical stability. They are slightly harder, and therefore may be a little more mechanically noisy. Stocks may still exist somewhere, though I have no idea where or who to contact - nor do I know which firm actually made them. (If you know who made them I would be interested to hear from you, as there is a definate demand for these products, albeit at relatively low volume.)

Offering what is perhaps the closest thing to a brand new roller, Geoff Kremer at ServiceSound is able modify pinch rollers from another type of tape recorder to fit the Series/Logic 7. These are complete pinch rollers and do not require an old hub for exchange. He is still working on a similar solution for idler wheels. Contact ServiceSound for the latest information.

Option 2 is now available from a number of sources: Roger Chippendale is able to cast a new urethane tyre onto the original metal hub. An alternative source is Terry's Rubber Rollers, in the US. Contact details for both are at the bottom of the page.

Suitable for idler wheels only, and for owners with the necessary DIY skills, an interesting alternative to a full rubber tyre is to make a metal ring with rubber o-rings to provide grip. Graham Lill has written an article describing how he did this.

Option 3 works, though of course only for idler wheels. If you take them from, say, an old mono deck of 1950s or 60s vintage (though I wouldn't advocate scrapping those machines for this purpose) they will work in the later decks. The profile of these earlier idlers is slightly thinner, but the diameter and bearing size are the same.

Lastly, if you find that replacements are not available at present, or you consider the cost prohibitive, don't throw out an otherwise good machine which could give another ten - maybe twenty or more - years of useful life because of this particular problem. Replacements may again become more readily available and, in any case, the market in vintage audio may make it worth your while to hold on: it's a long time since Ferrograph was fashionable, and therefore valuable, but things do change...

Links.

Recast rollers by Roger Chippendale (UK): E-mail .
(Please note that Roger may take some time to reply to enquiries as his main occupation can take him away for extended periods).

Terry's Rubber Rollers (US)

ServiceSound - Tape recorder repair and service by Geoff Kremer


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