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06-14-2020, 11:11 PM   #16
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QuoteOriginally posted by stevebrot Quote
The key might be that the M/P/O variant probably was limited to support of protocols that were essentially similar on cameras having similar contact patterns. The Minolta shoe was very similar to Pentax and the OM-2 shoe unique from either. I suspect that the pins were energized or read as if any of the three supported camera types were attached.
The pins are in different positions, but you may be onto something in that the voltages for Minolta, Pentax, and Olympus were the same or similar, and therefore Vivitar only had to make extra pins and a few extra solder points and wires in the shoe.

Minolta eventually went rogue with an entirely different shoe, as had Nikon earlier with that over-the-rewind-knob hot shoe.

06-15-2020, 06:49 AM   #17
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QuoteOriginally posted by Alex645 Quote
The pins are in different positions, but you may be onto something in that the voltages for Minolta, Pentax, and Olympus were the same or similar, and therefore Vivitar only had to make extra pins and a few extra solder points and wires in the shoe.
I want to say that is the case - that I've read or found that all three Ready pins are connected, but it's been so long that I don't remember. The technology is so simple that it could only be duplicated today with a quad-core ARM processor running Linux. 😀
06-15-2020, 07:10 AM   #18
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On one of the now defunct Yahoo Minolta groups someone had found or published a document on the pinouts, voltages and signal structure of the Minolta TTL flashes. I may still have a copy somewhere buried in a backup somewhere. If it's on tape however I longer have a tape drive.

As I recall, most likely incorrectly, the voltage was 3 volts DC. One pin was used to signal when to "quench" the flash. The other was the "dedication" pin which would signal when the flash was ready, set the sync shutter speed, and signal by making the LED in the viewfinder flicker for flash exposure confirmation. I remember my Sunpak flash wouldn't flicker the LED even though the ok light on the flash would light. The viewfinder LED would light but not flicker and go out sooner than with Minolta PX flashes. Minor incompatibility.

Edit: Here's this, but it doesn't document the voltage and signal structure. It gives the voltages for the later iISO (Maxxum) flashes but not the earlier TTL.
https://www.mhohner.de/sony-minolta/flashcomp_techref.php

Last edited by Not a Number; 06-15-2020 at 07:18 AM.
06-15-2020, 08:08 AM   #19
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QuoteOriginally posted by Not a Number Quote
One pin was used to signal when to "quench" the flash. The other was the "dedication" pin which would signal when the flash was ready, set the sync shutter speed, and signal by making the LED in the viewfinder flicker for flash exposure confirmation.
That is pretty much how Pentax analog TTL flash works too. "Ready" is the initial dedication pin and goes high when flash is charged (camera responds by setting sync speed and lighting flash read); "mode" on the shoe goes high to quench. I don't know how "flash OK" is signaled for auto (the body already knowing for TTL).


Steve

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