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Topic: Estimated Magnetic Head Lifetime
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted August 25, 2018 11:14 AM
When I purchased a spare Eumig 800 series head back in 1990, the life of the head was stated to be 150 hours. This seems ridiculously low, but it is probably based on some percentage of high frequency loss, that is when the frequency response of the sound head falls significantly below the new head specs. It does not mean that you cannot run sound films beyond 150 hours,just that you will no longer be getting optimal performance. I have had Eumig 800 series heads that have worn to the point of very muffled and low output sound so that they are totally unuseable. Not sure how many running hours it took to get to that point, but it was very probably much less than 1,000 hours. Elmo heads just seem to last forever. The head pressure pads on the Elmo's are very easy to replace, and the exploded view in the GS1200 manual is pretty self explanatory. I don't think it requires any special level of expertise to do this job.
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The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj
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Maurizio Di Cintio
Jedi Master Film Handler
Posts: 977
From: Ortona, Italy
Registered: Jan 2004
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posted September 02, 2018 08:02 AM
Probably my latest post is affected by the fact that, being a filmmaker more than a collector, I used to post produce sound (even rather complicated soundtracks) on my film with Eumig projectors; this entails a lot of stop and go, rewind, check, re-try which probably encreases head wear to a certain extent. I guess if you use projectors for regular screenings without stops, this will result in longer head life. Nonetheless soound heads on models 926, 936, 938 and 940 are indeed softer than other models, especially series 800's. These heads are a little smaller than previously, and above all, the thickness of the gap material is inferior to Series 800's. More to it by carefully observing the contact area of these heads, you can see they are made of layers of magnetic metal bond together: there are 4 layers for track 1 and only 2 for track 2! This makes the latter not only softer but weaker than the main stripe's head inasmuch as the two layers might easily come apart and the head becomes useless even if it were brand new: I have seen a couple of these machines with the balance track's heads in such awful conditions; probably some hard prints/splices had passed through them, but the main head was still unscathed. So these heads are more fragile to the point I suspect there might have been a few production batches where something went wrong; probably the binding agent or something that makes the two layers prone to come apart. To avoid this, I applied a tiny quantity of superglue (in gel) to the sides of the protruding part of the balance track which should prevent damages like the one described. This and the use of a 2-track pressure pad ONLY and IF required, has greatly increased the life of this particular head (my first 926 had its head refitted in 1991). In the future I'll exert same precautionary measure should I have to replace it again (and - I am afraid - the time has almost come). If only we could find something similar to replace it!!!!! But these heads are very unusual and rather short in height, so to the best of my knowledge there is no replacement other than the original ones. Which are now scarcer and scarcer....
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Maurizio
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Maurizio Di Cintio
Jedi Master Film Handler
Posts: 977
From: Ortona, Italy
Registered: Jan 2004
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posted September 02, 2018 11:39 AM
To the best of my knowledge, Paul, you are right. Although perhaps in Germany, some specialized repair centre for our beloved euipment, might still have some spares; fact is these spares (if any) are not meant for resale: they are meant for the technician to install them in a projector. Therefore as long as retirement is still not an option, such technicians will be unlikely to offer these heads for sale. It's such a pity since these projectors are such fine machines they might go on indefinitely if it were not for their heads. But I take it you - Paul - use your S 938 primarily to screen features and this should help your sound head. The material used by Eumig is presumably permalloy but the problem does not lie primarily with it: after all Bauer/SIlma/Beaulieu heads are the same material... The problem IMHO lies in the manufacturing process which had not been thouroughly perfected at the time. Let's not forget these heads date back to an era when Eumig was about to have financial problems: lots of new products and ideas in the pipeline, but second thoughts too; R&D department probably was experiencing a lot of stop&go's, lots of pressure, and maybe the quality check left something to desire... We will never know...
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Maurizio
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Martin Dew
Expert Film Handler
Posts: 204
From: Henley-on-Thames, UK
Registered: Jan 2017
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posted September 02, 2018 02:38 PM
That's interesting information, Maurizio, thanks. Yes, Paul, unfortunately it looks like there are no more heads available for the Eumig 900 series now. Even John White, our brilliant Eumig engineer here in Blighty (who was a former employee of Eumig distributor Johnsons of Hendon) cleared out the Avco complete UK parts inventory last year, and sadly there was no box of unused 900 series heads, which he was hoping to find.
My friends at Eumig Museum helped me out last year because I'm helping them with a couple of projects. They managed to find me a slightly used set of heads but their search took several months, went outside Vienna, and involved contacting ex-employees in Salzburg and beyond. I actually felt guilty that they had worked so hard to recover a set for me.
There was a thread on here where Edwin Van-Eck had considered rebuilding the assembly, but he had apparently found it cost-prohibitive. The balance head on the first S938 which I bought in 2016 is starting to lose treble, so I'm assuming it's on its way out. Wouldn't it be great if between us we could find a solution to allow these wonderful projectors to survive with full functionality into the future?
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted September 02, 2018 03:11 PM
Yes that would be great Martin but if Edwin, with all his expertise, manufacturing facilities, and industry contacts has concluded that a new re-manufactured head is cost prohibitive, then we should not expect any.
Much as I love my 938 I know that in a few years it will end its days as a superb silent projector and I am convinced that, out of all my projector collection, the GS1200 will be the last stereo sound projector standing.
--------------------
The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj
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