Think I fried one of my keyboard lines

[Anthony Flack]

So, I was testing my game (using joystick), I tried to wipe some dust off the monitor with my hand, there was a static discharge, the CPC reset and now one line of the keyboard matrix seems to be jammed on, I guess.

Every time I switch on the CPC I get

7
Line does not exist
... followed by a string of joystick left input

Now I don't have a working CPC, this is a setback. Damn. I assume it's fixable, but I don't need to be dealing with this right now! Oh well. Bit of a worry that static discharge...

Oh yeah, it's a CPC6128 I'm talking about here if that makes any difference. Seems to be otherwise working but unusable.

[pelrun]

Yeaaaah, I did *exactly* that as a kid. Dad was less than pleased, though to be fair it's not something I could have reasonably predicted or avoided. Had to send it away for repair (they actually just replaced the PCB completely.)

You've damaged the AY3 and will need to replace it.

[Anthony Flack]

Figured it would be something very much along those lines. I'll order another AY3. Anything in particular to look out for when getting one? ($30 postage from Australia, what the hell?!) I guess I could yoink one off one of my arcade boards but no, I won't be doing that.

Meanwhile, I was upset enough at being without my CPC that I went and bought another one. From France. C'est la vie. My existing one is a little bit tatty anyway and clearly, it pays to have a spare. 

[pelrun]

Getting original AY3-8912's is hard these days. If you can find one it'll probably be the -A variant which needs extra resistors added (if you look right next to the AY3 in your 6128 you'll see an unpopulated row of solder-filled holes - you want to stick a 2.2K 9-pin SIP resistor pack in there).

Alternatively you can get an emulated replacement from vRetro that should be a drop-in replacement if you're not too precious about it. https://www.vretrodesign.com/products/ay-3-8912-functional-equivalent

[Anthony Flack]

Nice! I'm not too precious, I'll give the emulated replacement a go. It will be interesting to compare.

[Brocky]

i remember doing that a couple of times back in the day... soldering a joystick while it was plugged in and cpc running! ...sound still worked.. just some keys would throw wrong key..or even combos...
i dunno how tbh.. but the PIO was replaced to fix it... possibly even the 74LS145 decoder...not sure.. but AY3 was fine...i just remember the PIO being socketed and a different brand when i got it back from repairer!

[pelrun]

There's certainly a chance that the PIO/145 that are damaged; I thought that the joystick port went only to the AY3, but I just checked and COM/COM2 pins go to the PIO.

Given that joystick-left is constantly pressed when the machine is turned on, I think it's unlikely that the AY3 is unscathed. If replacing it doesn't solve all the issues, then at least obtaining the other two chips is significantly easier.

[Anthony Flack]

I think it actually is triggering all the keys in line 2 of the matrix in sequence.

Cursor down, F7, return, |OURE, esc, and finishing on endless joy left. That whole column is cooked I guess.

Anyway, we'll see what arrives first and take it from there...

[Bryce]

I think it actually is triggering all the keys in line 2 of the matrix in sequence.

Cursor down, F7, return, |OURE, esc, and finishing on endless joy left. That whole column is cooked I guess.

Anyway, we'll see what arrives first and take it from there...

The entire line is read from a single input pin, so if that input is fried, everything on that line is either always pressed or never pressed.

Bryce.

[ajcasado]

@Anthony Flack , You can also consider the solution from this topic to replace the damaged AY:
https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/ay-3-8910-adapter-for-amstrad-cpc-to-stop-exploitation-for-ay-3-8912!/

[Anthony Flack]

Hey, you know I did wonder if somebody 

I think it actually is triggering all the keys in line 2 of the matrix in sequence.

Cursor down, F7, return, |OURE, esc, and finishing on endless joy left. That whole column is cooked I guess.

Anyway, we'll see what arrives first and take it from there...

The entire line is read from a single input pin, so if that input is fried, everything on that line is either always pressed or never pressed.

Bryce.

Yeah I figured. I don't know if that makes any difference as to whether the PIO is involved? I haven't so much as looked at a circuit diagram yet as I'm busy and also want to get the game finished, but I'll get to it.

@Anthony Flack , You can also consider the solution from this topic to replace the damaged AY:
https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/ay-3-8910-adapter-for-amstrad-cpc-to-stop-exploitation-for-ay-3-8912!/

I ordered the emulated AY as I was kind of curious to see it anyway and they weren't charging mad money to post it to me, which I appreciate. I did wonder if somebody had made an adaptor for the 8910 though, if the 8912 is getting so rare. So that's nice to see. I would probably have got that, otherwise. But it's good to just be able to order something and be done with it.

Anyway, my 6128 already had a slightly dodgy left cursor key from too much Dragon Attack, and rather than spend too much time, I spent some money. I love my CPC so it will be good to have a backup one. Parts or computer, it's going to take a couple of weeks to get here either way. If the chip gets here first I'll probably get impatient and solder it in. 

[McArti0]

I would start by unplugging the keyboard.

Maybe this Pin only lost its internal Pullup, just add a resistor to Vcc.