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..

SQLGuy 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.


I don't understand how a replacement chip could be epoxied in, and no soldering is required.

FWIW, I spent many years as a bench tech doing all sorts of electronic repair, including Sony cameras.

Here's one example of bad solder (in a Minolta "beer can"): https://pbase.com/pganzel/image/35488865

Very helpful, thanks for sharing.

The chip comes with the the contacts all in one piece

The chip with the contacts

So basically making space for it by removing the contacts and part of the the mount with a dremel tool. It will act independently of the previous (destroyed) connections.

Obviously, this should be the last resort as there is no way of going back.

I will try and remove the mount and see if there is any obvious bad soldering.

I live Newcastle, UK. Today I have unsuccessfully made a few phone calls to find someone who can deal with similar.

If I could use the original chip and contacts that would be a dream. I may also try and get some experience by dismantling another cheap lens mount and play with circuit board ..


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