Minolta 300mm F2.8 (Older APO, not HS), Chip?? Some help please..

Started 8 months ago | Discussions thread
OP Badrmino Forum Member • Posts: 82
Re: Minolta 300mm F2.8 (Older APO, not HS), Chip?? Some help please..

toni wrote:

User5049779158 wrote:

toni wrote:

User5049779158 wrote:

SQLGuy wrote:

The chip on these is just a PROM. It allows the camera to read lens data, and the current focus distance from some encoder contacts that manipulate which values will be returned from the PROM.

A common problem with many of the Minolta AF lenses is that the solder on the flexible circuit board that connects to the mount contacts is bad. It may just need to be resoldered


Yes it seems to be the problem.

I have got great help from Neil3 and other members here and on dyxum

The agreement is that resoldering is both technically difficult and can easily go wrong.

The replacement chip, which I have ordered now, will just need a space to be made for it to be epoxied.

The method has been successfully implemented.

For future reference here is the link ;




If it's a case of resoldering it should be reasonable easy to do with the proper tools - adjustable temperature soldering iron, start at lowest temperature.

The chip in question is attached to the lens mount and minimum disassembly is needed to reach the parts.

You could also do some measurements to chech current continuity on the flex board, and resistors.

Thank you very much.

I will ask around to see if I can find someone with experience. Just wondering if you could share any (dump proof) link that you bring the picture closer. I think it is worth trying while waiting for the replacement.


The post you have shared show where the electronics are. What I was trying to say was that it should be possible to debug the circuit and determine where is the fault. If you are lucky it could be something like SQLGuy shared or the smd resistors gone bad.

If it is indeed the chip, it will be harder to find a replacement. Going the James Lao seems to be the only available option.

For seeing what I was referring here is the image. Those 3 flat black devices on the left are the smd. You can also see the 5 soldering places that connect to the mount. Before assuming the chip as gone bad it should be possible to test the circuit for connectivity.

Great, thanks for sharing

Now I have some idea of what needs to be done.

If there is no obvious soldering issue can I not replace those SMRs regardless of testing either by new ones or from other lens (if they share the same code)?


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