Norman 202 Pack
If anyone out there has or knows the Norman 202 pack--There are two settings--100 and 30. 100 splits the two outputs 100/100 W-s. On mine, the 30 setting seems to split them 60/30 W-s. In other words, output 1 is a stop brighter than output 2. Is that supposed to work that way, or is something wrong with my pack? I know they've made packs that were designed this way for easy portrait setups, but I wasn't sure about this one.
I use mine with two lights on a copy stand, so I need equal output from both lights, and rather low output at that. I've solved the problem by using a splitter and connecting both lights to the stronger output, but I'm still curious about how it should work.
An interesting thing that I've discovered, incidentally, is that an LH-2 head needs about 25 W-s to fire consistently. Below that they get unreliable, in that they don't fire every time, and they don't always fire with the same light output.
speedotron and norman use similar electronics on the power side, as do most studio flash generators. There are voltage doubler or tripler circuits to boost the charging voltage to the main capacitors.
Typically there is a pair of capacitors as the minimum per circuit- it is easier to increase the voltage in both positive and negative potentials simultaneously, rather than building a single ended capacitor bank.
Usually there is a whole bunch of main capacitors in larger units. My 2400ws has 12 pairs. The power switches usually bridge between different banks. For me 2 pairs are 400w/s, 4 are 800w/s, and 6 are 1200w/s. The switches combine the banks.
So in the case of the Norman, I suspect that one switch setting puts 100w/s across all sockets, and the other setting isolates the banks, so that one socket(s) gets 66 w/s and the second socket(s) get 33 w/s.
I have carefully (- I am an electrical engineer - I wouldn't recommned too many others to peel a flash generator apart) modified my unit to be able isolate the 1200 w/s bank, to allow me to put lesser amounts of power across the sockets without needing splitter cords.
my real name, imagine that.
Thank you, Michael Wilde. The last paragraph with its warning is well done. I second your warning about opening and working on the inside circuitry of electronic flash units. My sense of authority to speak on this comes from being an ET who does dabble in restoring multivibrator circuits to normal function to make electronic flash units operate again.
If you are not knowledgeable and somewhat experienced in working on high voltage circuitry, DON'T. The voltages inside even small battery operated electronic flash units can be several hundred volts. If you get across it, you will feel it. You will probably react to it. Even if the electrical shock does not harm you, the involuntary muscle contractions you will experience may knock you down and can throw you across the room. This can lead to injuries from simple mechanical causes.
If you have ever turned off your electronic flash unit, and watched it, you may have noticed that the little "flash ready" light will continue to glow for several minutes afterward. The capacitors inside will continue to hold a charge for a fairly long time. Just turning the unit off will not make it safe immediately.
If your electronic flash unit does not work, and checking the fuses or replacing the batteries and checking the contacts and cables does not restore it to a working condition, consider taking it to a shop for repair. I really do not want to see you with your arm in a sling at the next photographer's gathering, or a photograph of you in a pine box.
Ralph Javins, Latte Land, Washington
When they ask you; "How many Mega Pixels you got in your camera?"
just tell them; "I use activated silver bromide crystals tor my image storage media."
I'm not planning to take anything apart. I just want to know if it's doing what it's supposed to be doing. I can also e-mail Norman, if no one here happens to know. I have other Norman packs, so I know how they work in general, combining the output of multiple capacitors or distributing the output among multiple heads.
The total output of a 202 pack is 200 W-s, and I can measure the relative flash output with a flash meter, so the 100 setting is like 100+100, where I can get 200 W-s through one head plugged into one output with the other one empty, or 100 W-s through each of two heads by plugging one head into each socket (or two into one socket with a splitter).
An interesting aside is that one head is more efficient than two. I can get about 1/3 stop more light from one head at 200 W-s than from two heads at 100 W-s each, though of course two heads at lower power give a shorter flash duration, if that's useful. I haven't tested this with my other strobe units, I suppose because I don't usually need to worry about getting 1/3 stop more power, but next time I do need lots of power from my big studio strobes, I'll check.
The "30" setting seems to be 66/33 as Mike suggests, but my question for anyone who actually knows this pack is whether it should be that way (and I could see why it might be), or should I have it checked out.
On Some Strobe units including the Norman 202
There are three basic ways to get the power capacitors in a strobe up to the correct voltage, 1. By a high voltage transformer, 2. By a voltage tripler circuit using a ladder of diodes and capacitors. 3. High Voltage Battery (510vdc battery) The Norman 202 has one power capacitor charged with a transformer's output rectified with diodes to a DC Voltage. The 202 has two output sockets and a switch that either delivers the same voltage to each or switches in a "resister" in the lower (darker) side. Because part of the power is attenuated by a resistor the total output in the 150/30 mode will be less than the 100/100 selection. In addition to the differences in the selected path with or without resistor, variances in flash tubes (resistance during flash) can cause a difference in output. Balcar used the difference between their short and long "U" shaped flashtubes to create a ratio of 1::2 in outputs. If you use a tube rated for 400w/s vs. 200w/s the resistance may be different and the output therefore different. At the time the Norman 202 was first introduced trigger voltages were the 70 to 200vdc range for many of the units. The Norman LH4 head had circuitry in the head stepping down the voltage and indicating a ready voltage via a "neon" lamp. I use either a "slave sensor" or a Quantum Radio trigger when working with digital and older flash units.
IMPORTANT -- Because of the high voltage coupled with high amperage in a power pack, leave the repair to authorized service providers. Norman has a list of service providers on their website.
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Thanks for the extra info!