AY-3 8910 adapter for Amstrad CPC, to STOP exploitation for AY-3 8912!

[TotO]

@eto My answer, just because I see it overlap the PPI on the picture.

[ikonsgr]

I just make a more thorough test:

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But now i discover  another problem, the back of the keyboard (and possibly a plastic safety clip) hits on the 8910 chip! But i think this can be resolved if, instead of using a 40pin socket, we solder the 8910 directly on the adapter board

[eto]

Can I put a normal socket into the area of the AY-3-8912? Or is it again one of those ICs where Amstrad decided to make it a bit wider so no normal socket will fit?

I also had a look at my 6128 and compared the available space to a normal DIP socket. Maybe I am missing something but I think if we move the 8910 a bit more towards the keyboard connector, then it would fit perfectly in between the keyboard cable and the capacitors.  

see attachment

[ikonsgr]

Can I put a normal socket into the area of the AY-3-8912? Or is it again one of those ICs where Amstrad decided to make it a bit wider so no normal socket will fit?

Indeed, it seems that all sockets are a bit wider, but if you use sockets with flat pins then you can plug them ok. Sockets with round pins however,are rigid and can't be installed.

[ikonsgr]

I also had a look at my 6128 and compared the available space to a normal DIP socket. Maybe I am missing something but I think if we move the 8910 a bit more towards the keyboard connector, then it would fit perfectly in between the keyboard cable and the capacitors. 

I suppose you mean something like this:

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This should free one electrolytic cap from bending.

[eto]

I suppose you mean something like this:

no. more like this. 

This one does not have the second I/O port, but that could be added on the right, if required. 

[ikonsgr]

Ah, now i see, you move the 40pin socket downwards instead to the left 
I'll see to it and upload the new gerber files then.

[eto]

I had to order some PCBs anyway so I measured the available space and designed a PCB. It seems it fits exactly into the free area. The distance between the two rows of the 28pin socket are slightly wider so it should fit into the motherboard without bending the pins. Of course this adapter will then not fit into any other computer but the CPC. 

I will try it out as soon as my AY-3-8910A ICs arrive and let you know if it's a fit. 

[eto]

I could test and verify today that it fits into a 6128 without bending a capacitor. It works as expected. 

Unlike the version of Iconsgr, this one is without I/O port B and it also will only fit into the CPC range as the socket is slightly wider than in other computers.

Gerber files attached. 

[SerErris]

Very good for a cheap replacement. There are also the YM2149s available that are compatible (clones) of the AY-3-8910 ... so the market should be really much better then the AY-3-8912s  even if the chip is in principle more powerfull.

Absolutely fantastic project.

[TotO]

Sure, the YM2149 is compatible (and even cheaper). I have used it into my X-CPC and ITX-CPC for tests some years ago, but it doesn't sound exactly as the AY.

[SerErris]

Ah oh, I was not aware of that. 

This indistinguishable sound of the CPC :-)

[eto]

Don't you need twice the clock speed on the YM to get similar sound output? Afaik the first divider stage on the YM is 32 cycles vs. 16 cycles on the AY.

[TotO]

Don't you need twice the clock speed on the YM to get similar sound output? Afaik the first divider stage on the YM is 32 cycles vs. 16 cycles on the AY.

It is not related to that. The YM use a 5bit envelope and the sound it not exactly the same for the same note at the same octave.

[Rabs]

Should any replacement also guard against ESD from the joystick port? I have just replaced an 8912 on a 664 and they are not cheap, 8910s not much better. Maybe any daughter card can also include ESD protection?

[eto]

Should any replacement also guard against ESD from the joystick port? I have just replaced an 8912 on a 664 and they are not cheap, 8910s not much better. Maybe any daughter card can also include ESD protection?

It probably makes more sense to make an ESD protection for the Joystick port directly. It then will also protect 8912, not only replacements after the original 8912 has already been destroyed. 

[GUNHED]

Yes! My first CPC got destructed when I touched the screen and joystick port in the same time by accident (that was short after I got it). More than only the chip was destroyed, even the tracks on the PCB jumped up. It needed to be completely replaced.

[eto]

I checked the different mainboard versions and some of them have capacitors that are connected to each of the joystick port pins. I guess they are there to provide ESD protection.

Would it be an option to just add capacitors to the mainboard, e.g. by using the resistors-array soldering points next to the AY? 


Another option could be a small PCB that is soldered to the back of the mainboard. For the C64 there are plenty of PCBs, e.g. this one: https://www.hackup.net/2020/08/esd-protection-for-the-c64-control-ports/

For the CPC of course we would need a slightly different approach as we have to protect 9 pins and don't have GND or VCC on any of the pins. Also SMD soldering is required. 

Btw: do we need to protect the IC 74ls145 (pin 8 and 9) also or is that one more robust?

[eto]

PCB for CPC incl. second I/O port has been delivered and tested.

It fits exactly into the available space of a CPC 6128 without bending capacitors. Due to the space constraints, the second I/O port soldering points did not fit on the right side of the AY. You can see their position on the picture attached.

I have a few spare PCBs here, so if anyone needs one, I can send a PCB for 3€ incl. international shipping as a letter (no tracking). Just send me a PM.

[GUNHED]

Great piece of hardware!