AY-3-8912-P Sound Chip Replacement?

[Purity]

Hey everyone, I'm sure this has been asked before but I couldn't find a definitive answer in searching.  I need to replace the AY-3-8912 on a CPC 464.  I know the AY-3-8912A will not work as a replacement but was wondering if the AY-3-8912-P was ok?  Anyone had any experience with this chip as a replacement please?

[SRS]

Here https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/sound-chip-on-cpc-plus-(ay38912ap-vs-ay38912p) ToTo says something about it needs some soldering ... "Because the "A" version require an external 2K2 resistor network to pull-up the GPIO pins. "

[genesis8]

You can get a clone for cheaper than by buying a second hand AY :

https://www.genesis8bit.fr/archives/index.php?news_id=2040

[eto]

ou can get a clone for cheaper than by buying a second hand AY :

https://www.genesis8bit.fr/archives/index.php?news_id=2040

They are currently sold out and they will not be cheaper if you consider shipping costs.

There are 3 options for a 8912 replacement:

• used 8912A with resistor array
• used 8910A with adapter PCB
• new clone

The 8910A is potentially the cheapest solution but you also need to order the PCB and components. If you need to order all of it, it's price is somewhere around 15-20€, depending on where you buy the IC. The 8912A will cost you around 25€ incl. shipping. The new clone is just 15€ but it's currently sold out and shipping probably adds 10-15€ on top.

[Purity]

I have an 8912A.  Is there any info on what I need to do regarding the resistor array?

[eto]

Is there any info on what I need to do regarding the resistor array?

There were a few discussions but I don't think it's explicitly documented somewhere. 

On some CPC mainboards there are soldering points for the resistor array. Seems Amstrad already anticipated to use the 8912A. On the 464 they usually do not exist, so you somehow have to solder it directly to the right lanes. Maybe the backside of the mainboard or to a socket.

[Purity]

Cool, thanks for this.  Would a 1K resistor array be ok?

I'm surprised no one has created a board that can sit in a socket to allow you to use the AY-3-912A.  I might look at doing that if this works well

[eto]

Cool, thanks for this.  Would a 1K resistor array be ok?

I'm surprised no one has created a board that can sit in a socket to allow you to use the AY-3-912A.  I might look at doing that if this works well

I guess the benefit of such a PCB is minimal. 

1) Many CPC boards already have a space for the resistor array
2) it's quite easy to solder the resistor array to the IC pins directly - or use a simple in-between socket. 

Plus: There is a PCB which allows you to use a AY-3-8910(A) - the 8910 is extremely cheap and easily available.

[Purity]

Cool, thanks for this.  Would a 1K resistor array be ok?

I'm surprised no one has created a board that can sit in a socket to allow you to use the AY-3-912A.  I might look at doing that if this works well

I guess the benefit of such a PCB is minimal.

1) Many CPC boards already have a space for the resistor array
2) it's quite easy to solder the resistor array to the IC pins directly - or use a simple in-between socket.

Plus: There is a PCB which allows you to use a AY-3-8910(A) - the 8910 is extremely cheap and easily available.

Is this what is labelled NR001 on the main board?  Which resistor array value can go in here please?

[Purity]

Not sure what happened to my previous response but I was asking, if this is what is labelled NR001 on the main board?  Which resistor array value can go in here please?

[eto]

Which resistor array value can go in here please?

Somewhere 10k was mentioned, which I used when I replaced a 8912 by a 8910A. 

However I also read 2k2 somewhere. 

[Purity]

Does it go here, or is this for something else?

[SerErris]

Yes it does go there, with Pin1 in the lower square bracket. But you need to get the solder out first.

So if you have the luxury of a CPC 464 old mainboard, you still have the solder holes for the resistor array there. 

Just solder it in and your keyboard will work.

The problem is btw not that the sound chip will not work, but actually the keyboard will stop working if you do not have the resistor array (in chip or as here externally).

Another option is:

Buy a AY chip and solder the resistor array directly on top. you only need to bend the +5v line. 

[Purity]

Perfect thanks, I'll solder into the board and let you know how it goes

[Purity]

This worked perfectly!  Thank you for the guidance!