(A500+) Ctrl + Amiga + Amiga does not work.

[rkauer]

 No need to change the keyboard.

 Look for the 3rd wire (looking on the motherboard connector, left to righ), normally a red one.

 It is the reset wire.

 Using a wire jumper (with Amiga turn on), short it to the thin shield somewhere. The Amiga must reboot. If so, you have the reset transistor burned (just change it to another equivalent), but first check the wire itself (it may have a bad contact on the connector).

[rkauer]

 Checking again the keyboard circuit, the reset line/wire is connected to the pin #8 of the 74LS27 chip on the kb board.

[rkauer]

Protek wrote:
So, stating the obvious here, swapping the chip does the trick?

 If the chip is faulty, yes.

 Better check the line with a multimeter first (at dc voltage measurement). When the Ctrl+L-Amiga+R-Amiga is pressed, the chip logic issues a "0" (zero) voltage to that pin.

 Simple case of open the Amiga, keep everything in place, turn it on and measure the voltage level on the pin (with and without the key combination pressed). Just be careful to not short the pins on the chip. Better measure the voltage right on the red wire.

[rkauer]

sim085 wrote:
Hi again,

I opened my amiga today and I do not have any chip marked as '74LS27'. However I have one marked as 'HD74LS27P'. Is this the same chip? Also since this is a chip and not just a transistor is it still easy to find?

 Yes, HD is the manufacturer "code", 74LS27 is the chip code (a TTL-LS chip) and P means some sort of revision. But prefer to swap the TRANSISTOR before change the (inexpensive) TTL, since it's easier to do.

 The transistor (one of those funny black things with 3 legs under it) can be replaced by a BC547 series. Just notice the BC547 have the pins "backwards" compared with the 2SC1815 (C1815 on the transistor itself). The middle pin have the same function. The probable culprit is branded "Q2" on the keyboard board.