A500 Memory Expansion - KCC9111

The memory expansion board sometimes is labelled KCC9111. This particular one is branded with that, but is exactly the same.

Battery Corrosion

As you can see from the pictures, there is battery corrosion from the alkaline battery that has already been removed.

When fitted in to an A500 rev 6A, it will boot to the Kickstart screen. However, when trying to boot Amiga Test Kit (ATK) from internal floppy drive (DF0) it fail to boot. It tries to seek to track 0 three times and stops. The usual suspect are the ram chips nearest towards the battery.

Luckily the ram chips are all socketed. Removing all the chips you can see that the 5 sockets nearest the battery has corrosion in the sockets.

The green corrosion was cleaned up with fine needle file, wire brush pen and isopropyl alcohol. Ideally, white vinegar should have been used to neutralise the alkaline first - but I didn't have any.

Memory Chip Testing

I labelled the chips - 1 to 8 for the top row, left to right; and 9 to 16 for the bottom row, left to right. I tested each chip, one at a time, in a another well known working memory expansion card, using ATK.

I mark the ones that either caused the A500 to not boot up, or failed the memory test.

Out of all the chips, as suspected, the 5 nearest towards the battery (9 to 13) all failed. With number 11 (third one in from the left of the bottom row) the one causing the floppy boot issue.

These 5 faulty memory chips will need replacing.

Board Testing

To test that the board and sockets are OK, I put in 16 known working ram chips. The expansion board booted and loaded ATK fine and passed 100 rounds of memory test.

RTC

However, the RTC chip was not being detected. I tested the RTC chip in a known working expansion card and that it was detected OK. With these boards, when the battery is removed, the 12V is not being pulled down and is supplying over voltage to the RTC chip. Once the resistor (at bottom and middle of the board in the picture above) is removed, then the 12V that is used to charge the battery is disabled and the RTC chip is detected again.

Although the RTC is working, it does not keep time when the Amiga is switched off. A new coin cell battery will need to be put in to allow the RTC to keep time when the Amiga is not switched on.

Fixed and Working

The board is now cleaned, with replacement memory chips, and resistor for 12V line removed.

Tested with ATK and memory and RTC are working. Only missing a coin cell battery for the RTC.