Film-Tech Forum ARCHIVE: DIY Reverse Scan

This is topic DIY Reverse Scan in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=004813

Posted by Paul Trimboli (Member # 1509) on 04-21-2003, 08:54 AM:

Has anyone made their own reverse scan reader?
What would be involved that would make it really difficult? Without doing much research at this point would't it only require you to take the cell out and place a bright red LED in its place and have a power supply for that. Then have the cells behind the slit lens where the exciter lamp was? Does it require a special lens? I know it also needs a pre amp in there. I just sound like the reverse scan kits are very expensive and I wondered why.

Posted by Mark Gulbrandsen (Member # 72) on 04-21-2003, 09:56 AM:

Yes, I've made one for the DP-70 that works very well. However it uses a standard off the shelf pickup assy and the standard Dolby LED. All in mounts of my own design. I'm presently working onone for the DeVry XD which is a favorite of home film collectors. The XD reverse scanner, which I've had numerous requests for, will be available starting in about a week.

The idea of the whole thing is to rid yourself of the slit lens...which in itself is the cause of many problems. You will find that you either have to use the Dolby red LED or a JAX light as the light source. A laser is also possible but is the more costly route.
Mark @ CLACO

Posted by Ken Layton (Member # 133) on 04-21-2003, 10:44 AM:

The Dolby LED is not just one single extra bright LED, but rather a bank of around 20 little LED's inside one case. This is to evenly illuminate the full width of the soundtrack. That's why the LED is so expensive.

Posted by Bill Langfield (Member # 818) on 04-21-2003, 02:24 PM:

Ken, I've got a feeling Paul is only asking, because he is working for someone/company or dare I mention it a 'Corp' who expects him to do EVERYTHING for nothing (ie His being there, being paid, should fix everything) - Been there, done that, DAMN we all still ARE, DOH!

That said, I too wonder about it DIY LEDS (reverse or not) to get around the now magneta and soon cyan sound tracks.
I'm still using light bulbs at a location, that work fine (for now), only changed a few in 3 years.

However at another location we are replacing these 'DOLBY LEDS' every six months.
Thank god the Pent 701 readers here use a light bulb.

How about...

Could not a 1-3 mwatt ruby laser with a custom lens do the job of simply replacing the exciter to handle ads/trls, then allow DTS (if you get the damned disc) to kick in for the feature?

Bill!

Posted by Mark Gulbrandsen (Member # 72) on 04-21-2003, 08:31 PM:

"Could not a 1-3 mwatt ruby laser with a custom lens do the job of simply replacing the exciter to handle ads/trls, then allow DTS (if you get the damned disc) to kick in for the feature?"
_________________________________________________________________

Bill,
A laser will work and yes you need as special lens to size the beam for soundtrack scanning. Its all much more expensive than the Dolby LED though.

Hopefully technical people that visit this site never but never think on the terms that the analog is just for trailers, or optical backup. But unfortunately many have been led to think this way.....but is plain stupid thinking and anyone with this sort of attidude obviously does not give a dam about their quality of presentation or their customers. In reality the analog chain should be as good as it can possibly be. There are many, many analog only prints out there. BFGW was one that ran at lots of locations for way more than 20 weeks and was SR analog only. Analog can sound as good or in some cases even better than digital and there are no tracking, or reading problems with analog. If I built a new plex for myself tommrrow the analog playback equipment would probably get quality precedence over the digital part of the systems. You'd hear analog tracks played back in my theatres that you would think were digital!! Also, You'd never believe how many DTS and Sony units get sent back to us or the factory for repair and they are then without their beloved digital playback system and are forced to run analog for some lengths of time.
Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 04-21-2003, 09:23 PM:

701 uses a led the 700 is a quartz lamp
There are many laser type readers out there
Ernamann has one
ACL has a line of them
and there is a line made in japan

Posted by Brad Haven (Member # 954) on 04-22-2003, 06:35 AM:

bill said :
Ken, I've got a feeling Paul is only asking, because he is working for someone/company or dare I mention it a 'Corp' who expects him to do EVERYTHING for nothing (ie His being there, being paid, should fix everything)

Paul is actually doing it for himself, he's working on a personal project. Good onya Paul, wish i could help but it's out of my league.

Posted by Peter Hall (Member # 695) on 04-22-2003, 12:33 PM:

Good laser kits are available for fair cost - ours lists at around $500. Considering these are rated at 20k + hours (I'd be keen to see an LED reach 10K) these arent a bad investment over time. www.fproj.com/cyan

Posted by Mark Gulbrandsen (Member # 72) on 04-22-2003, 03:20 PM:

Since we have reverse scan kits over here in the US at the 500.00(give or take a little depending on the dealer) price range I never opted to go with any of the Laser kits.

IMHO just getting rid of the tiny troublesome split solor cell makes changing to reverse scan worth the price alone. The superior audio quality one gets is then another benefit of the conversion. Lasers are ok but do not completely rid the system of other trouble points.
Mark @ CLACO

Posted by Paul Trimboli (Member # 1509) on 04-23-2003, 07:53 AM:

I guess you could say it is a personal project Brad. I am getting my RCA Photophone soundhead soon and my Simplex Standard head and a stand, not sure on the model of the soundhead though as Lindsay Morris says it has the motot mounted and right angles and it is mono.

What I want to know is, how does reverse scan work. Is there ONE LED at the drum (going of what the reverse scan unit we had installed at work in one of the cinemecanicas)? What is in the pick up part? What kind of lens?

I am thinking of going laser reverse scan, lasers at around 10mw are about $20 for the diode and lens, can solder it into a housing that costs $4. So if I mounted that where the cell would go, what kind of lens do I need after the film and is there a split cell after that lens in the pickup?

Any other information anyone can give me? Any info on reverse scan aligment. I was told that a properly set up foward scan vrs a reverse scan has the same S/N and sound quality ect? I can see how this would be true, since the foward scan in cinema 2 at work was re aligned and a new slit lens installed it sound magic!