(A500+) more keyboard problems

[Lockon_15]

Left Shift and left Amiga key could share same bus contact and perhaps if their common trace is damaged, that could be the reason for that local malfunction.
Dissasemble keyboard in pieces and try to take a look at thin black traces on both inner parts of keyboard matrix. Sometimes an excess dirt could cause printed conductive trace to lift-off and thus result in defect of more keys together.

Did you replace that dead transistor ?
IMHO, both of those on that small PCB can be replaced with 2N3904 or maybe 2N 3906, not sure exactly which type is (NPN or PNP).

[Lockon_15]

Traces are printed on each transparent plastic foil in the way that each trace on one side stay safe from traces on the opposite side, when both foild are strapped together (justs like sandwich).

You should track that traces in close vicinity of mentioned keys and check if some part of trace is damaged, missing or got moved to opposite foil (I had exactly that kind of issue last month).

[Lockon_15]

You have to compensate for that, i.e. make sure to establish good conductive properties of that failed line(s).

In short, get a pen with conductive ink - many electronic stores have it. Then make two or three thick passes until you get a visible, dense line, again.

Or maybe just get a spare keyboard (without keys and metal casing, to reduce cost on freight). You need small PCB - printed circuit board (stuff in upper right corner which connects to A500 motherboard) and plastic membrane/foil which can be detached/attached from PCB and rolled for smaller package format.

[Lockon_15]

@Zac67

Yes, that's the proper procedure to follow, but he said last event showed left Shift and left Amiga keys are out. If he cannot work out on those issues, there's no point on getting feet wet on broken transistor or 74LS27, right ?

Replacing a dead Q2 isn't a big deal, but '27 could be a real PITA for a unskilled (un)solder attempt...

Best regards

[Lockon_15]

You can safely use any functional A500 keyboard connected to any fucntional A500+ motherboard.