8mm Forum: Eumig 900 sereis head replacement

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Posted by Paul Adsett (Member # 25) on April 07, 2015, 02:05 PM:

Anybody know the procedure for removing and replacing the sound head on the 900's?

Posted by Andrew Woodcock (Member # 3260) on April 07, 2015, 02:28 PM:

I have never bothered getting a service manual for the 938 yet, why whats wrong Paul?

I am certain Maurizio will have an answer for you Paul.

Posted by Maurizio Di Cintio (Member # 144) on April 07, 2015, 02:58 PM:

Thank you, Andrew, for the faith. And congrats to Paul: you must have found a spare, then. OK, first of all, I assume you got just the head, without assembly, wires etc. So you'll have to recycle everything whch is not a big issue. Bujt you'll have to solder in the new sound head. To do that, you must remove the head assembly from its location beneath the lamp; proceed as follows:

1) remove the sound pressure cartridge and put the projector (I assume it is a 938?) on its rear cover for convenience
2) unscrew the two screws placed on the lower part of the head support; the right hand one first (it's spring loaded) then the left hand one. You'll have to tinker a little bit with the loop former on the right but that's no big deal.
3) It is advisable to also remove the heat shield under the lamp: there is only a little screw holding it in place which you can access from the lower left side of the lamp holder
4) Now you should be able to pull out the whole head assembly and take it as far a spossble from the machine; beware: it might require applying some strength and you might be tempted to remove the pinch roller too, which is not a good idea for two reasons: first it is a pain in the heck to put it back AND (two) it is possible to temporarily press it downward to make it easier to remove the head assembly

5)now you have in your hand the assembly, the first thing to do is to remove the hum shield which incapsulates the whole head: there are some tiny screws on top of the assembly which hold in place a "Y"-shaped presser on top of the shield.

6) after removing the presser, you can lift the shield and move it as far as possible from the head's top

7) Now all the solderings are visible: take note of ALL the wirings, and desolder all wires.

8) unscrew the two screws placed horizontally on the head support from its left side: this will allow removal of the old sound head; see to it not to lose the two tiny bolts inserted in the side "arms" from the head

9) put those tiny bolts in their respective slots in the new head and replace (keeping the sound pressers cartridge in position can help preset the right position of the head relative to its mount)

10) solder the wires and put the hum screen back.

11) reverse the remainder of the previous operation steps and once you are all set, load a film with good stereo sound; if the film does not thread automatically, do not worry: the azimuth of the whole head assembly is not correect yet; do some trial and error while turning the left screw mentioned at point 2, until the film loads correctly.

12) now all you have to do is to turn the same screw as the previous point, clock/anticlockwise until you achieve the best sound output from both tracks (both in terms of level and trble tone).

Enjoy. [Wink]

NOTE: the huge improvement in the replacing of the head as opposed to Series 800 is the fact adjusting the azimuth is that simple as all other parameters (tilt etc) are automatically set by the way the sound head engages the recesses on the pressers section: the both are built so that they match like Lego bricks...
If you have any questions, just ask.

Posted by Andrew Woodcock (Member # 3260) on April 07, 2015, 03:03 PM:

You're THE MAN Maurizio! [Wink]

I have copied and pasted your excellent Tutorial Maurizio. I will now archive it in my Eumig folder for future reference thanks!

I knew you would come up with the goods for Paul mate!

Posted by Maurizio Di Cintio (Member # 144) on April 09, 2015, 03:25 AM:

Indeed I am sort of fancing recording some videos of certain CLA practices but time is always a concern: you have to find it not just for these time-consuming activities but also to record shots from different angles, close-up's etc plus edit... That would a real tutorial. Also the 'right' machine has to come handy as I don't like to perform unnecessary maintenance on them. Perhaps next time I have to replace something, I'll consider finding the extra time involved in all this.

Posted by Paul Adsett (Member # 25) on April 09, 2015, 07:19 AM:

Thank's so much Maurizio. Yes Andrew I do have a spare head coming to me, thanks to Jonathan Trevithick in Australia - how great the people are on this forum. [Smile]

I was hoping the head would just plug in like it does on the 800's, but I am sure I can do the job anyway with Maurizio's detailed instructions.

Posted by Maurizio Di Cintio (Member # 144) on April 09, 2015, 11:04 AM:

In the meanwhile, I was able to replace the motor on my latest S 940 and could test the sound section: unfortunately my guess regarding the head was right: track 2 is much lower than 1 in both output level and high frequencies (almost muffled sound); that's the clear hint track 2 head is going towear out completely very soon...

Paul, do you know if the head you are going to reeive comprises the ancillaries too (head mount & wirings)? Beacause in that case you only have to fit it in place and tune up the azimuth (no need of soldering, which is the worst part of the job IMHO).

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