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Moving Vintage Norman 200Bs into the Modern Era…

**** UPDATE *****

UPDATE:  NEW DESIGN COMING SOON THAT REDUCES CURRENT IN THE CAMERA/TRIGGER SWITCH AS ~20mA MAY BE TOO HIGH FOR CAMERA INTERNALS.

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This post needs to be prefaced with a major disclaimer: Open your Norman 200B at your own risk. The 500V inside is potentially lethal. The author was careless once and accidentally discharged the cap with a meter probe which caused a big char streak in the connector and took a hunk out of the meter probe and one of the head plug pins. Proceed/attempt at your own risk. If you die, break your 200B, or both, I am not responsible.

Now that that’s out of the way, on the to the good stuff.

The Norman 200B trigger voltage is on the order of 100V. It was fine for old film cameras with mechanical sync switches. Modern digital cameras don’t care for such high voltages, so some sort of conversion or adaptation needs to be made. Optical slave triggers are one way to go, but the author smoked one accidentally by just letting the 200B sit waiting to flash. Apparently, some modern optical slave triggers do not care for such a high trigger voltage either. They are also going to end up dangling and exposed where they can become disconnected or in the extreme, get broken off.

Slave triggers and the like are not inexpensive, either. Sure, they come encased in a nice little plastic package and all, but at $8-10 or more apiece, they add up quickly, especially after having acquired four complete pack and head sets. Sometimes, it’d be useful and nice to use all that fire power at the same time and not have to carry all those little slave triggers and wires and stuff…

So, what to do? Reverse engineer the trigger circuit and make and a low voltage adapter for it using piece parts… Here’s the photo of the board alongside a mirrored and colorized photo of the traces on the bottom side that was used:

Norman 200B controller board

Here is the partial trigger circuit (please ignore all the extraneous numbers and notations) of the stock 200B blue circuit board:

Norman 200B LowVmod-5

Observant readers of Harold Edgerton’s book, Electronic Flash, Strobe, will notice that this circuit is pretty much the opposite of one within his book. The difference is that the Norman 200B is uses a positive ground, so everything is upside-down in comparison to Edgerton’s circuit. Another thing that should be noted is that when the SYNC connection is grounded, the charged 0.02uF capacitor discharges, turning on the gate of the SCR. Only a small amount of current will flow if the SYNC connection is held grounded, probably as an added safety benefit.

One would think that adding an optoisolator across the SYNC connection and the chassis would be sufficient to adapt the 200B for low voltage operation. That was tried but it did not work because the current that flows is too small to latch the triac within the optoisolator ON, so the capacitor does not discharge quickly enough, and the 200B never triggers. An early attempt to correct this consisted of shorting the diode. When the two resistors dividers are shorted together at their center points, the 200B could be fired with an optoisolator between SYNC and the case. But then additional current flows unnecessarily from the high voltage supply.

The first incarnation of the low voltage adapter was built into a plastic Tic-Tac and hung off a house hold plug that was plugged into the head. A sync cord then plugged into the Tic-Tac trigger. It was too many connections, something extra to carry and/or break. So when the opportunity to use two of the Normans for a photo shoot presented itself, it was time to move the adapter inside the pack and make the outside connections simpler…

In order to hook this into the 200B, three parts on the blue controller board need to be removed: a diode and two resistors. The colored circles indicate where the tap points are for the adapter board. The three parts need to be removed to completely isolate the SYNC connection to the head so that only optoisolated low voltage goes to the head socket. Note that two of the removed devices have a colored circle on one of their leads. The third one is unmarked in this photo but it is to the right of the orange filter capacitor and +12V connection (it can be seen in a later photo).

Norman 200B LowVmod

Here is the schematic for the low voltage adapter:

Norman 200B LowVmod-4

And here is the parts list with Digikey part numbers:


Digikey part number
Description
Note
497-2960-5-ND
IC REG LDO -5V .1A TO-92
negative 5V regulator
160-1378-5-ND
OPTOISO 400VDRM TRIAC OUT 6-DIP
optoisolator, MOC3023
CF18JT180RCT-ND
RES 180 OHM 1/8W 5% CF AXIAL
I limit resistor
399-1249-1-ND
CAP CER 0.1UF 50V 10% X7R 1206
output cap
399-1285-1-ND
CAP CER 0.33UF 25V 10% X7R 1206
input cap

The negative 5V regulator is probably not absolutely necessary, but the most often quoted number for DSLR maximum sync voltage I’ve seen is on the order of 7-9V; 12V would then be too high. A negative regulator is required because of the positive ground design of the 200B. The two capacitors are required by the regulator; surface mount chip caps were used because they take up a whole lot less room. The 180 Ohm resistor limits the current for LED inside the MOC3023 to about 20mA.

The circuit was wired onto a small perforated prototype board as can be seen below on the left. The board is positioned in this photo so the devices can be seen. The bottom of the board is normally up when assembled into the pack.

Norman 200B LowVmod-3

The pack assembled with the “protective” plexiglass cover can be seen in the photo below. The protective plexiglass is often broken on these old units… The cover also does not afford a whole lot of protection anyway since fingers can still get at the high voltage. I typically keep my fingers well clear when the power is applied and for a long while after the power is turned off as a precaution.

Norman 200B LowVmod-2

 

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Posted in diy by david on February 2nd, 2013 at 4:26 am.

3 comments

3 Replies

  1. greg aiken Dec 14th 2013

    hi, ive heard from brent at holly enterprises that norman’s 2000ws tube is driven from 900 vdc and the ‘flash igniter trigger’ is 12 kvdc.

    might you have these same specs for the portable battery powered 200 ws tubes? he has told me the 200 ws tube is driven from 450 VDC , but i forgot to ask him about the voltage used for the ‘flash igniter trigger’. if you know this spec can you please tell me?

    also, by chance, i dont suppose you have available a photo of normans ‘original’ battery that was supplied with the P200B? i am making notes for myself, and i no longer have an original battery, so cant take a photo. if you do have a photo, perhaps you could email it to me to be included in my docuyment (of which i am happy to send you a copy). gregaiken@hotmail.com

  2. Actually, the 200Bs charge the caps up to about 485V (500V is typically the figure used, but the service info I have says to set the HV shutoff to 485V).

    I do not have any of the specs for the FT120 flash tube but from what I’ve read, it is a 250Ws tube. The voltage across the tube can be ~400-700V. The trigger voltage can be something like 6kV to 10kV.

    I don’t have any original Norman batteries or photos of them. I had a battery but since it was dead when I got it, I ended up recycling it and keeping the connector and thermal cutoff switch.


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