Modified 35mm Sound Heads

#1 by Ian Partridge , Thu Mar 17, 2016 12:10 pm

I am familiar with optical sound with exciter lamp and photo electric cell systems, however I am new to the red laser? mirror and photo diode sytem found on 35mm sound heads.

What is "Solar cell"

Is this a red light system?

Ian


 
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RE: Modified 35mm Sound Heads

#2 by Deleted User , Thu Mar 17, 2016 2:02 pm

Ian,
Solar cell is not a red laser (led) system.
They were used on the Philips DP 75 projector in the 70's .
Basically does the same function as the photo electric cell
In converting the light from the soundtrack into sound.
Also there's stereo solar cells for Dolby Stereo sound.

Regards
Tony


Tony Laing


Last edited Thu Mar 17, 2016 2:20 pm | Top

RE: Modified 35mm Sound Heads

#3 by Hugh Thompson Scott ( deleted ) , Fri Mar 18, 2016 12:54 am

Ian, apart from the excellent information imparted by Tony but my faux pas on missing out Gwyn, this poor bugger is still in harness,I apologise to all you 35mm men,
I am still a little lad in the minor stuff



Hugh Thompson Scott

RE: Modified 35mm Sound On Portacine 35 ?

#4 by Ian Partridge , Fri Mar 18, 2016 3:36 am

Many thanks. I believe I will receive friendly advice here in my quest to sort out the sound on a Cinemeccanica Portacine 35.

It seems that fitting an original Portacine built-in amplifier may not be the answer if the sound head has been upgraded to something different?

I will upload some pictures of the sound head.

Ian


 
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RE: Modified 35mm Sound On Portacine 35 ?

#5 by Gwyn Morgan , Fri Mar 18, 2016 9:45 am

Ian ,I assume that the projector has been with a red LED for reading cyan tracks as well as the older stereo tracks.
I'm not aware of having any compatibility problem when changing over.Has someone messed with the amp and replaced the original amp and messed with the wiring.If so then you need more expert help than me ,im sure someone on here will be able to help.
Yes a couple of pics may help📽📽


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RE: Modified 35mm Sound On Portacine 35 ?

#6 by Ian Partridge , Sat Mar 19, 2016 5:49 am

Gwyn,

You are right about the original amplifier box being removed, with odd wiring and loose unsecured components with a 12volt guitar amplifier board, pre-amp module, 5 volt and 12 volt power supplies. It seems that this was for sound monitoring only with the sound output from the head fed to an external sound system. There is optical sound coming from this arrangement but a lot of distortion that I believe is hum and harmonics generated by the odd wiring and amp and not the optical track itself which sounds crisp and clear. The red optical reader side looks to have been professionally set up to read the sound tracks including cyan tracks

The seller of a 35mm split spool I contacted recently turns out to be a previous owner of this same Portacine. He confirms that the guitar amp was for monitoring only and that the sound pick up fitted was one of the best available. It originally had a power source specially designed and matched to the sound head. Unfortunately this is no longer present.

I have acquired two spare original Portacine internal amplifier units from Italy.One is working and I have replaced all the internal rubber wiring which had perished so I now have a working mono amplifer that could fit the machine as intended.

But I will not use it until I am sure that I can safely connect the red optical output to the optical input of the original Portacine amp. I know that on the Cinemechannica c55 separate amps they had a switch for normal photo electric cell optical sound and 'diode.'

The sound head fitted has a red light deflected by an angled mirror beaming a 'grid' shape square of red light (not a slit) onto a small square plate below the sound drum.

I will try to upload the photos soon.

Ian


 
Ian Partridge
Posts: 97
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Date registered 08.18.2015
home: Colchester, Essex. United Kingdom
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