>From Gene Poon on Yahoo group. Sincerely,
C. Brendemuehl ***************************** > The Vivitar 550FD M/P/O (Minolta/Pentax/Olympus) is a medium power > bounce-head flash with TTL capability, for use with all Pentax > cameras with or without flash programming. It has its own sensor for > autoflash, so it can be used with the screw mount models, the K > series and the MX/ME, with the user setting X-sync shutter speed and > aperture. It has the simple flash program for the ME Super, MV, > etc., where the camera will automatically set the X-sync shutter > speed when receiving a "ready" signal from the flash and the user > sets aperture. On the Super Program, LX, etc., it will do TTL flash > with auto aperture select and auto shutter speed select using the > camera's internal sensor and Pentax's ANALOG communications link > between camera and flash. On the autofocus Pentax cameras, it is > SUPPOSED to be able to do full TTL programmed flash with auto > aperture select and auto shutter speed select via Analog > communications, but on most of them, one of the pins used for > dedication to Minolta or Olympus cameras causes spurious signals to > be introduced to the autofocus Pentax body via the digital contact in > the hotshoe. This interferes with the control circuitry of the > autofocus Pentax. Depending on the camera model, the effect may be > improper exposure; an unstable shutter speed, switching at will > between X-sync and ambient; or a lockup of the camera's circuitry > until the battery is removed (if you are lucky, there may be no > effect at all, but that's not what I normally see). > > This is a shame; the Vivitar 550FD M/P/O is a lightweight and > reliable flash unit; if it didn't have this anomaly with the > autofocus bodies, it would be usable with both manual and autofocus > Pentax, and could be considered to be an "almost AF280T" lacking only > a rotating flash head and viewfinder "Sufficient Flash" indication; > and that function is included, on the rear panel of the flash, > instead of in the viewfinder. It's inexpensive in the used market; > while the Pentax AF280T is a current Pentax model generally selling > in used condition for $50 and up on Internet auctions, the Vivitar > 550FD M/P/O can generally be had cheaply. > > It is easy to modify the Vivitar 550FD M/P/O internally to eliminate > this interference with the circuitry of the Pentax autofocus bodies. > Yes, one could tape off the offending contacts, but the sharp tips on > the pins will wear through the tape in short order. NOTE: this > modification involves minor disassembly, and work with some small > wires inside the bottom of the flash. If you feel you may have > difficulty doing it safely, refer the job to someone who is skilled > in this kind of work. > > First, for safety's sake, you MUST discharge the storage capacitor by > switching the flash "ON" and to the "M" mode, and then discharging > the flash using the "READY/TEST" button, switching it off IMMEDIATELY > without any delay. Remove the batteries and let the flash sit for > 24-48 hours, which should bleed off the residual voltage on the > storage capacitor. > > Remove the mounting foot by unscrewing four screws. Be careful not > to lose the screws; if you do, don't use anything longer as a > replacement since there is circuitry inside the bottom of the flash > and you don't want a longer screw touching it. Gently pull the > mounting foot away, and notice the wiring on the inside of the foot, > to the numbered terminals. Do NOT touch the visible circuit board, > but note the wires connected to the pins marked "1" and "2". On > mine, the wire to "1" was purple, the one to "2" was white. Cut them > off the pins with a nail clipper or small wire cutting pliers; I > recommend leaving a small bit of the color coded insulation on the > terminal so you can reconnect correctly later on if you want to. > Using a small piece of tape, insulate the wires you cut, so they > won't touch each other or anything else. Put back the mounting foot > and the four screws. Put a small piece of tape inside the battery > door, marked "PENTAX ONLY" because the flash dedication won't work > with Minolta or Olympus any more unless you put the wires back. > > That's it. Now the Vivitar 550FD M/P/O will work with the Pentax > autofocus bodies, at least up to the MZ/ZX series (I have not tried > it with the *ist series, film or digital). Since I use both the PZ-1 > and LX, the 550FD is now ideal as a lightweight flash that can be > used in TTL automation with both bodies. > > NOTE: This only applies to the Vivitar 550FD in its M/P/O version; > the C/R and N versions do not have Pentax circuitry in them at all. > Also, the same modification works on the Vivitar Series One 600 > M/P/O, which is the same basic flash as the 550FD M/P/O but with a > rotating zoom head. -Gene Poon ________________________________________________________________ Sent via the WebMail system at mail.safe-t.net