Minolta Program 2800 AF flash: Dissection

[Andreas Thaler]

For study purposes, I disassembled a Minolta Program 2800 AF flash whose battery contacts were heavily corroded by battery electrolyte.

The flash belongs to the Minolta 7000/9000 AF system.

---

A word of caution

What we as DIY repairers WITHOUT electronics training should definitely not do is work on devices with high voltage.

This includes all electronic flash units like this Minolta Program 2800 AF, cameras with built-in electronic flash units and devices that are powered by mains voltage.

This poses a potential risk to health and life.

---

Access to two trim potentiometers under the cover plate.

There are no screws under the sticker.

The housing is clipped together. I pried it open without being able to find a starting point for the lever. It worked with force.

The flash electrolytic capacitor.

For safety reasons, I treat it as fully charged, which is unlikely given the corroded battery contacts.

For this state to be the case, the flash must not have been used for a long time and the electrolytic capacitor must have discharged itself.

In fact, I do not measure any voltage in the volt range.

One of the two circuit boards in SMD technology. The cubic control LEDs in red and green are nice.

I measure the flash capacitor again in the millivolt range: A harmless 4.6 millivolts are present.

The flash capacitor.

The second board with discrete electronic components. High voltages are present here during operation.

Above the flash tube.

Below are the LEDs for the AF Illuminator.

 

[Andreas Thaler]

Here you can see two inserts for the metering pattern that is projected onto the subject for focusing.

Details of the AF Illuminator, whose lenses are adjustable.

One of the transparent discs for the AF metering pattern.

---

Conclusion

• A lot of digital and analogue electronics are built into this advanced AF flash.
• The precise mechanics in the AF Illuminator are impressive.
• It remains a mystery to me how one can open such clipped-together housings without damaging them. A service manual with instructions would be helpful here.

+++

All information provided without guarantee and use at your own risk.

 

[koraks]

It's incredible how much engineering went into a 'simple' flash unit!

 

[Andreas Thaler]

Note on the voltage measuring range of my multimeter

The device shown can be operated up to a maximum of 300 V DC input voltage.

However, higher voltages can be present on a flash capacitor. The one shown here has a nominal voltage of 350 V DC.

I would not use it to measure a flash capacitor that has just been charged, but in this case it was assumed that the capacitor was empty due to the long standing time.

Exceeding the voltage measuring range of the multimeter can damage the device/be dangerous. The measuring probes used are also only safe up to a certain voltage level.

You have to think about all of this for your own safety.

 

[ogtronix]

I attempted to open one of these too and couldn't figure it out, and decided i'd better stop since i'd rather keep the thing as an ornament for now than destroy it.

Especially since I'd destroyed a 4000AF already trying to get inside of it... and i'd been feeling it's designed to be hard to open on purpose since they wouldn't want it to look user repairable with the gigantic capacitor inside.

Like the bottom computery half is fairly accessible with screws and connectors and such, but the top half with the motor and flash charging stuff is held together by tabs that have no room to flex and obscured screws under stickers.

I was kinda joking about these units being so (currently) cheap that you could treat them as disposable if their old capacitors don't last for long after being charged for the first time in 2 decades, like cheaper than running flash bulbs, but I wonder if disposability was the intent as designed.



Actually looking at that 4000AF again in the photos, the real tricky part was the bezel over the flash area and I think you could probably remove it sticking a thin spatula in from the inside of the bezel and pushing outwards... It's gonna bother me if I dont try it, even though I don't need to do it on my working unit...

Yeah that works, lol. That spatula is for getting APS film out of their cans, held together and varnished with superglue. Hence not storing it with optics. After removing that bezel, if I remember right, you can decouple the rack from the motor from the slidey part of the contraption to move it out enough to access more screws hidden under stickers. And stickers you can just rip off and replace with double-sided tape and nice paper trimmed to size I bet. I'm kinda invalidating my whole prior point...

 

[Andreas Thaler]

iFixit has cool tools for opening cases.

 

[ogtronix]

I've been tempted to see if their interchangeable precision screwdriver tips are any good since i've always wanted a good set of those. I think I was gonna mention that in another post but i'm trying my best to not ramble too much. If nothing else I appreciate their website for being the only guys willing to open and document the internals of the latest gizmos, even when they're real expensive like those terrible Apple goggles.