How are you protecting the operator from (at least) a nasty burn on the thumb?
> On 05 May 2018 at 02:13 "Dale H. Cook" <radiot...@plymouthcolony.net> wrote: > > > This group seems free-wheeling enough that you might enjoy hearing what I > have been working on for two days (although I will likely bore some of you > into hitting the trash can icon). It is a stage prop made using the guts of a > Vivitar 283 flash. > > Before any of you start screaming and cussing at me for cannibalizing a 283, > hear me out. > > This play needed a prop consisting of a small metal bowl on the end of a > short pole, with a strobe lamp inside the bowl rigged so that it would fire > when the actor pushes a button on the side of the pole. The metal bowl will > reflect the light outwards and upwards. One of the adults (this is a local > children's theatre company) asked at the only electronic parts distributor > left in town (30 years ago we had four distributors plus several Radio > Shacks) if they could do the job. They said that they could not, but > suggested that they call me. > > I told them to see if they could get someone to donate some old camera flash > units for the project. An out-of-town friend of one of the adults donated > three Vivitar 283 flashes, all rather sad looking, all missing their light > sensors, two missing their battery holders, and one even missing its hot shoe. > > Next comes some technical explanation that should be familiar to us senior > citizens but may be new information to the young folks in the group. I expect > that some of you have used a Vivitar 283. The original 283 from the late '70s > and early '80s was one of the seven wonders of the world of photography with > automatically controlled flash duration (controlled by the light sensor). > Even one in top condition today would be useless with most DSLRs. Old-school > film SLRs triggered the hot shoe by closing a switch connected to the shutter > button. Flashes of the day put 200-300 volts on the hot shoe, needing a > relatively stout switch to trigger them. That also meant that if you were > stupid enough to pull the flash off the SLR without discharging it you could > get a nasty shock from the flash. In any case the 283 does not support TTL > (through-the-lens) flash control they way that the better current speedlights > do. > > Today's DSLRs are generally designed for a much lower trigger voltage in the > 5 to 24 volt range. Some models of DSLR may be able to handle trigger > voltages up to 250 volts, but you had better be darn sure that yours will > before tying to use a 30-40 year old flash, as many cameras can sustain > electronic damage if you try to make them handle 200-300 volts on the hot > shoe. > > All in all those three donated 283s are useless for current use unless you > are using an old-school 35mm SLR, and even then none would control the flash > automatically since all three are missing the light sensors. > > It took me an entire working day yesterday to 1) show that all three properly > worked in manual mode (fortunately I had one battery holder), 2) find and > download the service manual (well worth the $4.99 I paid) and read it > thoroughly to familiarize myself with the circuitry (it is a complex beast), > 3) go out and buy some parts and components that I needed, and 4) do most of > the disassembly of my candidate, the saddest looking one which was missing > the hot shoe. > > Today I finished the disassembly and started removing bits and pieces that I > don't need, such as the automatic flash duration control circuit and other > gewgaws (if they had room they would probably have included a kitchen sink in > the design). I have been building the prop with some parts from my extensive > electronic scrapyard (I've been collecting electronics of various sorts for > nearly sixty years), a couple of parts bought at the electronic parts > distributor, and some physical components from the home center. I expect to > have it ready to demonstrate at tomorrow afternoon's rehearsal. It will not > be in finished form - it will be in what we radio engineers formally call > "proof of concept" stage. It will be ugly but will demonstrate how well it > works. Informally some call that the "chewing gum and paper clip stage," or > as I prefer to call it, the "baling wire and duct tape" stage. Note that > tomorrow some parts will, in fact, be held together with duct tape (but > probably no baling wire). It will be in its final aesthetically pleasing form > in time for the first dress rehearsal in a couple of weeks. > > My total investment will be about twenty hours of labor. At my going labor > rate for my most favored customers (I still work a little for some small > locally owned radio stations) that would amount to 10 Benjamins, and I am > donating the labor. The out-of-pocket cost for parts and materials is another > matter as they have no budget. Fortunately they have three of those Vivitar > 283s, so they will have a complete parts junker to keep the prop working and > I will get one as compensation for my out of pocket expenses. I will modify > it for a much lower contemporary trigger voltage (so I won't fry one of my > wireless triggers). The missing light sensor is no problem as I will add a > control to manually set the flash duration and I will use it as an off-camera > flash for fill or highlighting. It is a 2900 BCPS 5500 Kelvin unit which > should work well for me as a supplementary flash, and my mod will allow me to > manually select flash duration from 1/1000 to 1/30,000 of a second. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
