david_dicarlo

<p>Actually, an SCR is what controls this flash. While it's true that the tube won't shut off until the voltage drops below some value, an SCR will not turn off until the current flowing through it goes down to a low enough level. In the circuits I've seen with a variable output, the main SCR initiates the flash and another one shunts a capacitor across the first SCR which siphons off current to the point where the first SCR shuts off. </p>

<p>All in all, though, SCRs are relatively slow. Current flashes use IGBT transistors which can turn on and off pretty much at will. IGBTs are what allows Nikon's wireless optical remote control to work - their protocol sends out a series of extremely short lower power flashes to control the remote flashes.</p>

<p>If I get brave enough, I might build an IGBT controlled pack, either from scratch with a bank of caps or by gutting this 200B. But it'd be a rather ambitious undertaking...</p>

<p>According to the repair person I spoke to, he said the more likely thing is that the controller board was going and not the flash tube. But then a controller board service makes him more money than selling a replacement flash tube, so I may have just answered my own question...<br>

<br /> The after glow, when it occurs, happens at any power setting. There is no fractional ratio on the 200B - it uses a switch and a bank of capacitors to control the flash power. Very granular (50, 100, or 200 W-s) but simple and easy to implement. Nothing fancy like modern continuously variable power flashes of today.<br /> <br /> There does appear to be some electrode plating some on the inside of the tube where the electrodes enter the tube. It's directional. I don't know enough about flash tube to know if that's normal or evidence of impending demise. I found a reference to 800 W-s bulbs that fit the LH2 head, which allegedly would give faster flash pulses and costs just as much as a normal 200 W-s replacement one.<br /> <br /> In any event, I just traced out the wiring of the flash head, so I now understand what the connections through the cable are and are doing. If I can't locate schematics, I can continue to reverse engineer it myself. I'd just prefer not to...<br /> There are definitely two SCRs (one 16A and the other an 8A) on the board inside, three 741 op amps, three TIP-29 TO220 packaged transistors and two TO-3 transistors (undoubtedly the inverter switches) on the board. All the rest are passive components, two of which are trim pots.</p>

Does anyone have the schematics or service info for a Norman 200B portable strobe?

My unit does not always supress the afterglow and I'd like to attempt to fix it.

thanks,

david

<p>When a Nikon SB600 is dropped and no longer turns on, it is probably because the inductor has been broken, as in: <a rel="nofollow" href="http://www.nslms.com/2009/09/07/like-a-flash-in-the-pan/" target="_blank">http://www.nslms.com/2009/09/07/like-a-flash-in-the-pan/</a></p>

<p>The battery assembly free-floats in the case and has a nice little tight cutout area that fits just over the inductor. So if it is full of batteries and shocked, this inductor can easily be sheared and broken.</p>

<p>All is not lost- I just fixed mine for under $25 - but that's because I ordered the wrong size inductor to begin with and also ordered a copy of the repair manual and parts list off eBay. I've posted details of the repair at the link above, although it is not for the unequipped or faint of heart...</p>

<p>When a Nikon SB600 is dropped and no longer turns on, it is probably because the inductor has been broken, as in: http://www.nslms.com/2009/09/07/like-a-flash-in-the-pan/ </p>

<p>The battery assembly free-floats in the case and has a nice little tight cutout area that fits just over the inductor. So if it is full of batteries and shocked, this inductor can easily be sheared and broken. </p>

<p>All is not lost- I just fixed mine for under $25 - but that's because I ordered the wrong size inductor to begin with and also ordered a copy of the repair manual and parts list off eBay. I've posted details of the repair at the link above, although it is not for the unequipped or faint of heart...</p>