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One caution: In some battery-powered strobes with fixed flash rates, you may not want to change the flash rate nor the value of the energy storage capacitor, unless you change both in inverse-proportional manner. If you half the flash rate, you may need to also double the capacitance. Otherwise, the storage capacitor may charge up to a different voltage - potentially insufficient (causing dim and/or skipped flashes) or excessive. Before changing anything, measure the maximum voltage the storage capacitor actually charges up to, and be sure this does not change much.
In a few strobes, the trigger circuit does not use a timer circuit but senses the storage capacitor voltage. If this is the case, you can change the storage capacitor and the flash rate will largely adjust itself. However, there may be some delay from the time the storage capacitor reaches a particular voltage to the time the flashtube gets triggered. If the storage capacitor is decreased to get a faster flash rate, the capacitor may get charged to a higher voltage.
One other note: At lower energy levels, some flashtubes work most efficiently at higher voltages. If you decrease the storage capacitor and use a higher flash rate, you may want the capacitor value to decrease somewhat more than the time between flashes if this achieves a higher voltage, AND if the capacitor and the diodes used to charge it and the DC-DC converter's transistor will withstand higher voltages.
If you need to reduce the power delivered by the DC-DC converter to get lower power consumption or to reduce the voltage the storage capacitor charges up to (for smaller capacitor or slower flash rate), try a lower input voltage. If you are daring and/or know what you're doing, you may be able to find a resistor to replace with one of a different value, typically larger if the DC-DC converter is a "ringing-choke" type. To increase power, there may not be much to do except increase the input voltage. This has the risk of burning out major parts of the DC-DC converter. If you succeed, you may need to increase the flash rate or the storage capacitance to avoid charging the storage capacitor to an excessive voltage.
Electronic Goldmine http://www.goldmine-elec.com sells flash and strobe stuff. Their Strobes icon leads to their flashtubes and other things such as trigger transformers and some assemblies. They also have strobe light boards and kits. One link useful there as of 10/7/2023 is here.
Then there are "disposable" cameras. CAUTION - their capacitors may be charged. Attempting to disassemble a disposable camera may trigger its board into charging its capacitor.
Radio Shack used to sell the usual U-shaped flashtube, with a catalog no. of 272-1145. I recommend getting the essentially identical BUB0641 by the company that is currently Excelitas, or the similar Miyata MFT-106MS, or similar flashtubes. I mention ratings for this and similar flashtubes here.
Mouser Electronics was found on 5/29/2020 as no longer having any xenon flashtubes that I previously said they sold.
The MFT-118 flashtube and a strobe assembly with the FT-34 / GN34 flashlamp are available from Sales Surplus of Nebraska.
If you need a higher power flashtube, you may be able to get these from some photocopier repair places and some camera shops that sell replacement flashtubes for professional duty photoflashes. You may need to supply a model number of equipment that takes the flashtube you want, or a model number for the flashtube itself. These places may not be too helpful if you only give a description or requirements.
Here are three flashtubes I am familiar with and that I have seen at camera and photo supply stores that cater to serious and professional photographers:
(Material on the FT-6 deleted due to being obsolete and largely unobtainable.)
1. The Photogenic C4-5 and C4-15. This is a ring-shaped quartz flashtube in a clear dome. Be sure you are getting what you want, since this may also come in color-corrected/UV-blocking versions and/or with diffusing domes.
This tube takes 500 joules well at 500 volts and 150-200 watts average power at least for a little while without forced air cooling.
2. The Speedotron model MW8QV or 14570. This is a really high power quartz flashtube used in Speedotron's "Black Line" Model 102 flash head. I have heard of a maximum safe energy of 3200 joules, and I have known it to take 1200 joules with no problem. It seems to be able to take an average power input of a few hundred watts long-term (hours?) and a kilowatt short-term (15 seconds?) with enough forced air cooling (attach it to a small vacuum cleaner?). Optimum voltage is around 900 volts to maybe a kilovolt. I tried to break mine with an average power input of 800 watts and no cooling - couldn't ruin it! But I caution that this tube may not survive that sort of abuse reliably nor for long. This tube triggers easily for a big one.
3. The Lumedyne 090Q is a medium sized quartz flashtube with big flashtube ratings and a price like that of the big ones above. Although it looks very well made, I consider the ratings awfully optimistic. It has a rating of 2400 watt-seconds and I can believe practically useful at 1200 and having good life expectancy at 400. Better than the FT-6 for medium to medium-large jobs, and the price may be worth it if you need the compact size.
I have more info on larger flashtubes in my Large Strobe Parts Page and more data on some of these tubes in my Flashtube Ratings/Data Page.
UPDATE 10/12/2023: A 400 volt electrolytic capacitor that has especially low ESR for its value is the 22 microfarad / 22uF Kemet ESG226M400AM5AA. Although its ESR of 1 ohm is high for photoflash and strobe capacitors, it is low for a 22uF electrolytic capacitor. Paralleling multiple ESG226M400AM5AA capacitors achieves ESR that is less than usual for the total capacitance of electrolytic capacitors. Five of these capacitors in parallel has capacitance of 110 microfarads and ESR of .2 ohm. Ten of these capacitors in parallel has capacitance of 220 microfarads and ESR of .1 ohm. The Kemet ESG226M400AM5AA is larger than usual for 22uF 400V electrolytic capacitors, which helps for avoiding overheating with higher flash rates. But in high flash rate strobes, I generally recommend non-electrolytic capacitors.
For electrolytic capacitors under 100 uF, some axial lead versions such as Vishay/Sprague's TVA series have less internal resistance than most PC-mount and "snap-cap" ("radial") types which can have enough resistance to noticeably reduce efficiency. Generally, most electrolytics in good condition and at least 220 uF and as well as ones specifically designed for photoflash use have adequately low internal resistance.
"Disposable" flash cameras have photoflash capacitors. The Kodak "Funsaver" has a 160 uF 330V capacitor. My experience has been that the "Max" has a 120 uF 330 V capacitor, but Sam Goldwasser reports seeing 160 uF ones in "Max" cameras. Flash cameras with Max guts (including the button to jump-start the flash charger) but of brands other than Kodak usually have the 160 uF capacitor. I found unmarked ones in Fuji cameras and store brand cameras.
For capacitors under 20 uF, you may want really conductive non-electrolytic capacitors such as oil-filled ones, "motor run" ones, or foil ones or "extended foil" types and ones rated for use in pulse forming networks. Repeated strobe duty usually heats up photoflash and most other electrolytic capacitors - you may want something else or at least to watch out for heating!
Motor start type non-polarized electrolytic capacitors are generally not good for xenon strobes.
For small capacitors of just a few uF or fractional uF, I recommend extended foil types and Vishay/Sprague 715P series (but not so much the other "orange drop" series), their 131P and 735P series, and Cornell Dubilier's WMF and MMWA series and the like.
Newark Electronics (800-4NEWARK, http://www.newark.com) and Allied Electronics (800-433-5700, http://www.allied.avnet.com) are good sources for capacitors, but have minimum order requirements and shipping charges and probably not the lowest price in the world.
If you watch for air conditioners (especially commercial duty ones) in the trash, you may be able to trashpick motor run capacitors. You may also find them and other oil filled capacitors in electronic surplus parts places and hamfests.
Digi-Key sells Panasonic dry film capacitors suitable for motor run use. Although I have not tested these, I believe the "Stack type" "SQ" ones are especially suitable for strobes! The 230 volt ones are highly reliable with rapid strobe duty to 330 volts DC and generaly reliable to much higher voltages. In general, motor run capacitors are reliable to a DC voltage at least twice their rated AC voltage.
I have heard of concern about blowing the internal fuses that some motor run capacitors have. So far in my experience, I have yet to blow one by discharging a capacitor with a flashtube. Putting two or more motor run capacitors in parallel will result in lower peak current through each capacitor and will further reduce the chance of blowing any internal fuses.
Capacitors to avoid include electrolytic "motor start" capacitors (these are usually junk) and some metallized film capacitors which cannot handle the high current surges of strobe use.
Update 7/2/2018: Digi-Key sells these. Look for xenon flash transformers.
Electronic Goldmine sells two trigger coils:
G9879, with three wire leads, $1.00 each
G9626, with four leads for PC board mounting, $1.75 each
Mouser Electronics was found on 5/29/2020 as no longer selling triggeer transformers, especially not ones that used to be mentioned here.
Radio Shack has one as a special order item - RSU-11996667, 99 cents.
You can make your own - Go here to find out how!
Digi-Key sells SCRs - I like the Teccor TCR22-6 (Digi-Key catalog number TCR22-6). For something really robust and immune to interference but only requiring 15 mA to fire, there is the Teccor S6010L, also available from Digi-Key.
Radio Shack's 276-1020 also works!
The TCR22-6 and the Radio Shack SCRs are "sensitive gate" models requiring only a few milliamps to trigger. Be prepared to deliver as much as 10 mA to the gate for reliable triggering unless you know that the requirement is less. Many Teccor sensitive gate models such as TCR22-6 only need .2 mA to trigger. Non-sensitive-gate SCRs require much more current still, 15 to maybe 80 mA for guaranteed triggering (15 mA for many Teccor models).
Written by Don Klipstein.
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