Film-Tech Forum ARCHIVE: Question on solar cells

This is topic Question on solar cells 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=005882

Posted by Mike Carro (Member # 232) on 02-22-2004, 12:50 PM:

I'm wondering if stereo solar cells ever lose their viability?

I'm using one that's probably 20 years old. I've noticed lately that analog sound isn't what it used to be. Overall clarity and fidelity. So, I thought I'd start at this juncture.

Thanks

Posted by Tim Reed (Member # 137) on 02-22-2004, 02:23 PM:

The cell could be dirty or cracked, but troubles like this are usually a result of the sound lens being dirty or out of focus.

(Btw, might want to change the name of the topic to something more descriptive than "Question for the experts". The forum disallows "teaser" subjects.) [Wink]

Posted by Bob Koch (Member # 1062) on 02-22-2004, 07:52 PM:

As Tim says if the cell isnt cracked or physically damaged it will last indefinetly. Your problem is probably oil in the optical or even in the slit. Check your scanning illumination.

Posted by Randy Stankey (Member # 64) on 02-22-2004, 09:44 PM:

In some of my old theaters they had Jax-Lites in their projectors. Okay, okay... We all know how crummy they are. You don't need to tell me. I still had to work on them, like it or not.

Besides the usual problems Jax-Lites gave me, I had some of them stop working for no reason even though everything checked out OK.

The system would suddenly lose gain at the preamp. The trim pots were all the way up and still nowhere near enough signal came out of the cell. I checked that damn preamp box in the soundhead but it was OK. Yes, the cell was clean. Cleaned it myself. No, it wasn't cracked. I checked.

After about a few hours of trying to figure out what the hell was going on, I called the boss and asked him.

He told me to move the solar cell so that the light beam was hitting a different part of the chip. I said to him that the beam was hitting the top 1/3 of the chip just like it's supposed to be. He said to move the cell anyway. Maybe to a point about 1/2 the way from the top. Once I did that everything suddenly worked OK again.

Our guess is that after a while, the part of the cell where the beam hits it all the time somehow becomes insensitive. Maybe it's the red light? We don't know. All I know is that moving the cell so that the light hit another part of it made it start working again.

Just another reason not to use those dumb things, AFAIC!

Posted by Gilbert Travin (Member # 2138) on 02-23-2004, 02:02 AM:

Hi !

Oh, yes a dirty optical system may damage the sound !

Have you also checked the shielded wires (they are sometimes damaged by oil) and the preamp ?

Posted by Warren Smyth (Member # 1838) on 02-23-2004, 04:27 AM:

What effect on the audio does a cracked cell have? Does it drop the level or can it cause distortion?

Posted by Mike Carro (Member # 232) on 02-23-2004, 09:39 AM:

I'll check for dirt,etc. Then I'll try to move the solar cell so that the light hits a different area as Randy suggested. For some reason that sounds logical to me.

Posted by Greg Mueller (Member # 17) on 02-23-2004, 09:53 AM:

Warren
If the chipped or cracked part is where it's trying to pick up the signal, it won't work well. I've used chipped and cracked cells, but just mounted them where the damage wasn't, and they worked fine. I think a lot of the time the chipping or cracking is from where the "mounter" ran the chip into sound drum, or maybe mounted them to close to the film so the chip was "scuffed" by the film over time.

Posted by Sam D. Chavez (Member # 1841) on 02-23-2004, 11:54 PM:

I've had situations where the cell was covered with a film from 409 or some other cleaner. Sound was OK but mono. Turns out the residue of cleaner was diffusing the light.

I've also had situations where the common on the solar cell was gone. You get normal Dolby level but no stereo as the cell in essence becomes a bigger mono cell.