This is topic Brain schematic in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Ken Lackner (Member # 1002) on 02-19-2002, 12:21 PM:
On the last page of the Strong AP operation manual, there is a very basic schematic of the brain. Does anyone have a detailed schematic of the phase control version? thx.
Posted by Paul G. Thompson (Member # 655) on 02-19-2002, 12:35 PM:
Ken, I never saw one either. May I presume you have one that is dying? If so, the rest of them are not too far behind.
I have converted all of mine to micros. The seem to be much more reliable over a longer period of time.
Posted by Ken Lackner (Member # 1002) on 02-19-2002, 04:58 PM:
Paul, I do not have Strong platters. If I did, I would convert them to micro switches as well. I am simply curious as to how they work. I like to know how things work. 
I'm also curious how they work because of my electronics classes.
Posted by Ken Layton (Member # 133) on 02-19-2002, 05:06 PM:
The schematic and repair info on the phase control are already on the manuals page under "Field Bulletins"-> "Strong phase control adjustment and repair". I drew the schematics myself and there are two versions of the phase control.
Posted by Paul G. Thompson (Member # 655) on 02-19-2002, 07:41 PM:
Ken, if you would like, I can send you a bunch of half-dead ones I took out of service. You can have them, free! Just pay the postage.
Posted by Ken Lackner (Member # 1002) on 02-19-2002, 07:53 PM:
Paul, sweet! Let me know how much.
Posted by Ken Lackner (Member # 1002) on 02-19-2002, 10:55 PM:
Ken, thanks for that. I had no idea that was there. Question about the schematic: Unless I'm reading something wrong, is the 1N4004 diode reverse biased? I don't get it.I assume that the symbols that look like diodes with circles around them are transistors? They look a little different than the transistor symbol I'm familiar with, but I can't think of what else they would be.
Posted by Josh Jones (Member # 447) on 02-19-2002, 11:33 PM:
if it is a diode in a circle with two legs coming out the other end it is an SCR or Silicon Controlled Rectifier. These are used to switch large currents with little input power. they are also used in cheaper lighting dimmers(more expensive ones use Diacs, which is just two SCR's back to back). Hope that helps,Josh
Posted by Josh Jones (Member # 447) on 02-19-2002, 11:41 PM:
Yup, just looked at the schematic and those two devices on the bottom near the (-) terminal are SCR's. The diode with two wavey arrows near it in a circle is an LED. the other diode in the circuit with the swastica for a gate is a Zener diode. they are used to provide a constant voltage source because their voltage drop and current draw will change with the voltage put across it.Josh
Posted by Phil Hill (Member # 371) on 02-20-2002, 01:19 AM:
Actually a DIAC is two diodes back to back and is used to prevent false triggering of a SCR or TRIAC. A TRIAC is basically 2 SCRs back-to-back so as to pass both halves of the ac waveform. A SCR is a controlled rectifier and as such only passes half of the ac waveform. Depending on the manufacturer and load requirements, a dimmer may use either a TRIAC or 2 back-to-back SCRs with the same results. It has nothing to do with cost.
Also, a Zener diode, the one that has the wavey cathode line and is biased backwards (cathode to +), is a constant voltage device. It is installed on a regulated supply line with a specific value series resistor to form a voltage divider network. It is rated in watts like the resistor. Thus it provides a constant voltage with changing current requirements and therefore must dissipate the excess voltage like a resistor as heat. >>> Phil
Posted by Ken Lackner (Member # 1002) on 02-20-2002, 11:42 AM:
I know that the zener diode is supposed to be reversed biased, but it looks to me like it is forward biased, and the LED and 1N4004 are reverse biased. Am I reading something wrong?
Posted by Phil Hill (Member # 371) on 02-20-2002, 05:31 PM:
Looking at the schematic it appears that the +'s and -'s are mislabled backwards and there is a connection missing between the anode of the zener and the (mislabled) V+ of the 334. >>> Phil
Posted by Ken Lackner (Member # 1002) on 02-20-2002, 10:16 PM:
"Looking at the schematic it appears that the +'s and -'s are mislabled backwards...."That would definitely go a long way in explaining my confusion. Thanks!