Film-Tech Forum ARCHIVE: leds for Strong Phase Controls

This is topic leds for Strong Phase Controls in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Rick Long (Member # 213) on 08-09-2002, 12:40 AM:

We have learned from experience, over the last few years, that leds used as light sources for level-sensitive equipment, such as digital and analog soundheads, do fade over time and require occassional re-adjustment.

This problem, however is not limited just to soundheads, but also to such equipment, apparently as Strong phase controls. These units, which when new pay-out film with no problem, suffer from considerable drag as they get older.

Our experience has been that fooling around with the on-board pot to bring up the led level provides only a temporary cure, and soon a replacement phase control is needed.

To me, it seems a shame to have to replace the entire phase control assembly if only the led is at fault.

To this end, will Strong please make available a replacement led for this unit?

Posted by Pete Naples (Member # 761) on 08-09-2002, 07:22 AM:

Surely (although I've never had any trouble with these as yet), the LED is an off the shelf device, available from any electronics supplier?

Posted by Rick Sanjurjo (Member # 1365) on 08-09-2002, 07:47 AM:

Rick,

The only LED I have a had to replace is on the DMC, the replacement part number for that is 2468249. If you are having troulbe with the phase control let me know and I will get you a part number for that LED.

Rick

Posted by Joe Redifer (Member # 3) on 08-09-2002, 09:41 AM:

Please post that part number here in the thread for other users who may have some need for it down the road.

Posted by System Notices (Member # 2357) on 09-09-2009, 03:50 PM:

It has been 2588 days since the last post.

Posted by Dominic Espinosa (Member # 2122) on 09-09-2009, 03:50 PM:

Anybody have the part number forf these?
I've got a bunch laying around and would love to repair in-house...

Posted by Joe Redifer (Member # 3) on 09-09-2009, 06:01 PM:

I found a bunch of 6-year-old phase control boxes that had been removed from our brains because the technician couldn't get them to work properly. They replaced them with microswitches. I do not like microswitches, so I put the phase control boxes back into service. No problems! What matters most is the positioning of the box itself vs the actual LED. Don't play with the LED much if you don't have to. Sure, they won't last forever, but they can last at least 7-8 years without any issues easily.

Posted by Gordon McLeod (Member # 33) on 09-09-2009, 07:02 PM:

i still prefer the micro switch

Posted by John Walsh (Member # 168) on 09-09-2009, 08:13 PM:

Don't be surprised, Joe, if they crap out fairly soon. I'm with Gordon; put the microswitches in. It takes a little time, but they can be set to pay out without the film actually running against the 'guard' rollers around the head.

Posted by Mark Gulbrandsen (Member # 72) on 09-09-2009, 08:26 PM:

Ditto, Using the right Microswitch I can get a microswitch equipped platter to run almost as smooth as a phase control platter can. I also have a mod that no one here has thought of that will get you 5 to 7 years out of your microswitches!!

By the way Joe, If those are the platters fomr SLC I AM the one that took those phase controls off...

Mark

Posted by Monte L Fullmer (Member # 2797) on 09-09-2009, 09:32 PM:

quote:
I also have a mod that no one here has thought of that will get you 5 to 7 years out of your microswitches!!

Is that the "snubber" trick - using a cap and a resistor?

And if so, what were the values of each component so I can do the snubber trick on our switched brains..

thx -Monte

p.s. (true Joe, I also love phase controls over microswitch - for I have one platter that I do use phase controls on and never had a hitch with that platter concerning payout problems..and these controls are over 20 yrs old. ... )

Posted by Joe Redifer (Member # 3) on 09-09-2009, 10:24 PM:

Mark, the platters I refer to are not ones from Salt Lake City. Plus, the old phase controls I have put back in have been running perfectly for nearly a year now. They don't even wobble. Most are completely still as they pay out. The microswitches stuck all the time. So much fewer problems with the phase control. Then again NO problems is always fewer than any problem. [Smile]

Posted by Mark Gulbrandsen (Member # 72) on 09-09-2009, 10:27 PM:

quote: Monte L Fullmer
Is that the "snubber" trick - using a cap and a resistor?

Nope. That actually does very little to prolong the life of the switch.

Posted by Jeremy Weigel (Member # 4208) on 09-10-2009, 01:17 AM:

Converted all our carbon switched brains to micro switches in 1995 and haven't had one fail yet.

Posted by Mark Gulbrandsen (Member # 72) on 09-10-2009, 04:20 PM:

Jeremy,

The switches made back then were alot higher quality and since the advent of lead free contacts they don't last very long. Also, I bet you are still running switches that are tensioned for acetate film.... not for estar film. There IS a big difference there.

Mark

Posted by Steve Guttag (Member # 268) on 09-10-2009, 08:15 PM:

I'll bet Mark is adding not only Cadmium but Lead for good measure to the contacts! [Smile]

Posted by Mark Gulbrandsen (Member # 72) on 09-10-2009, 10:45 PM:

It's highly possible that some of the components around the switch may have lead and cadmium in them.... I'm certainly not a true beleiver in lead free stuff...

Mark

Posted by Carey Barber (Member # 1586) on 09-11-2009, 12:39 PM:

What is the difference between a phase control and a microswitch platter system?

Can you tell simply by looking at them what system you have?

And finally, is the only difference between the two located inside the brain, with the rest of the platter system being all the same?

Posted by Joe Redifer (Member # 3) on 09-11-2009, 02:39 PM:

You can tell because the phase control will have a bigger box than the microswitch. Also, you can physically see the microswitch arm on said brains. When you swing the payout arm back and forth, you will hear a light "click" sound on a microswitch brain if it is working properly.

Phase control uses an LED and an optical sensor inside. As the payout arm moves, more of the LED is visible to the sensor. Basically, the brighter the light on the sensor, the faster it will command the payout deck to spin (depending on the takeup variac's position, of course). Usually this is only around 5 or 10% faster than the takeup is spinning if the decks are timed correctly. Phase controls usually offer smoother payout where as the payout arms on the microswitch will bob back and forth from on to off, on to off. Microswitches are at either 0% speed or 100%, no in between. You can use both on the same platter system and you can even remove the guts from a brain and replace it with the guts of the other kind (though most people forget to move the roller when doing so).

Posted by Jack Ondracek (Member # 1466) on 09-12-2009, 03:17 AM:

OK, so back to the original subject. Does anyone know if those LEDs are commonly available... like from Mouser, Newark or the like?

I think one of the past members, whos name I think is non-postable here [Roll Eyes]

has done this kind of work. I bought 6 phase control kits from him several years ago, & they've worked well for me.