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General Category => Technical Support - General => Topic started by: willow3411 on 19:58, 14 February 22

Title: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 19:58, 14 February 22
Hello,
My AY-3-8912 sound chipset from my CPC 6128 no longer works (no sound but the keyboard works fine). I can't find component 8912 anymore. we only find AY-3-8912A . but does it work? because pin two is not the same (not connected to A). Can adapt the 8912A on the CPC 6128? thanks in advance Willow
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: eto on 20:50, 14 February 22
Unfortunately I don't know if there is any difference. Actually I wasn't even able to find a datasheet for the A variant.

But maybe this helps. Seems it is in stock.
https://amigastore.eu/715-ay-3-8912-sound-generator-chip.html
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 21:07, 14 February 22
Thank you ! I also saw the link to order but I'm afraid it's A. on pin A #2 is not connected. on 8912 it is the TEST function. I have an A and it does not work on CPC 6128 (the keyboard does anything)
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: Nworc on 21:26, 14 February 22
The pin 2 is just a test pin and is irrelevant.

The difference between the 8912 and 8912A is that the latter does not have the internal pull up resistors on the output port. While the sound will work, the difference in the pull up resistors will interfere with the keyboard logic in the regular CPCs. Of course it is possible to work around this but that requires some soldering. I would prefer to buy the right type, which is much less effort. This is no theory, I've checked that with a test board.
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 21:40, 14 February 22
Oh yes ! welding does not scare me if you have a tutorial or explanation I am a taker thank you
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: Nworc on 21:58, 14 February 22
Ooops, what did I do   :o

Well, it's not that complicated, I mean?  You would just add the pull-up resistors externally.  The question is just: what value should they have.  I just don't know - you would have to experiment.  Maybe that information can be found in the specs of the non-A type if you find it, or somewhere in the service manual of the CPC.

However, I must express my displeasure at the fact that people here are obviously toying with the idea of tinkering with a historical cultural asset by means of a quick and dirty repair. I cannot endorse this!  :picard:
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 22:01, 14 February 22
Hello,

The AY-3-8912/A has the same pinout, but it require to add an extenal resistor network at the proper place on the CPC 6128 mainboard to allow the keyboard and joystick to work properly.


EDIT: You can use a 2k2 resistor network. It is not dirty to do it, Amstrad does.
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 22:05, 14 February 22
Quote from: Nworc on 21:58, 14 February 22
Ooops, what did I do   :o

Well, it's not that complicated, I mean?  You would just add the pull-up resistors externally.  The question is just: what value should they have.  I just don't know - you would have to experiment.  Maybe that information can be found in the specs of the non-A type if you find it, or somewhere in the service manual of the CPC.

However, I must express my displeasure at the fact that people here are obviously toying with the idea of tinkering with a historical cultural asset by means of a quick and dirty repair. I cannot endorse this!  :picard:
thank you very much The problem is not dirty repair, but the fact that I can't find AY-3-8912 on the market anymore. Suppliers only deliver 8912A
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 22:07, 14 February 22
Quote from: TotO on 22:01, 14 February 22Hello,

The AY-3-8912/A has the same pinout, but it require to add an extenal resistor network at the proper place on the CPC 6128 mainboard to allow the keyboard and joystick to work properly.
Ben precisely, that I understood well, and it is this diagram which I would like to find with the values ​​of the resistances.
Thanks
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 22:12, 14 February 22
And a picture to show that. 2K2 works fine and you just have to put it on the good way.
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 22:24, 14 February 22
Very good job !!!
But the way ? I don't look....
thanks
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 22:47, 14 February 22
Here where is located the common of the 9pin (8+1) resistor network.
Before you ask, there is probably a white dot on it to know the good pin. :)
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: Nworc on 23:58, 14 February 22
Quote from: willow3411
Quote from: Nworc
However, I must express my displeasure at the fact that people here are obviously toying with the idea of tinkering with a historical cultural asset by means of a quick and dirty repair. I cannot endorse this!  :picard:

thank you very much The problem is not dirty repair, but the fact that I can't find AY-3-8912 on the market anymore. Suppliers only deliver 8912A

Sorry, my humour might be a bit too dry to get noticed   ;D
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 11:48, 15 February 22
Quote from: Nworc on 23:58, 14 February 22
thank you very much The problem is not dirty repair, but the fact that I can't find AY-3-8912 on the market anymore. Suppliers only deliver 8912A

Sorry, my humour might be a bit too dry to get noticed   ;D
Everyone has their own sense of humor Don't worry, it takes more than that to upset me. :)
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 11:58, 15 February 22
Quote from: TotO on 22:47, 14 February 22
Here where is located the common of the 9pin (8+1) resistor network.
Before you ask, there is probably a white dot on it to know the good pin. :)
sorry, I had not seen well :). on my map it was a bit hidden. Do you know where I can find this component? thanks in advance
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 12:17, 15 February 22
it's a good ?Thanks
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 15:12, 15 February 22
Yes, the one printed 2K2 is OK.
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 15:56, 15 February 22
perfectthanks
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 19:13, 18 February 22
Quote from: TotO on 15:12, 15 February 22
Yes, the one printed 2K2 is OK.
Goodnight all . A little background on the repair. A huge thank you to all of you (especially TotO). Everything works perfectly with the network of 2.2K resistors. On the other hand Attention: Amigastore.eu supposedly sells AY-3-8912 but they are copies (made in taiwan) and they do not work!! thanks again here are the photos
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 20:26, 18 February 22
Great!  :)
Next time, think to order some sockets!  ;D
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 20:29, 18 February 22
Quote from: TotO on 20:26, 18 February 22Next time, think to order some sockets
Yes the supports are on order but still late in France!!!
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 20:45, 18 February 22
It was faster that I send you one.
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: Nworc on 00:42, 19 February 22
Quote from: willow3411
On the other hand Attention: Amigastore.eu supposedly sells AY-3-8912 but they are copies (made in taiwan) and they do not work!!

Excuse me, I cannot believe that this is a "bad copy". What I see on the photo is a genuine chip made by General Instruments, produced in Taiwan. Taiwan is not China, Taiwan has a high tech industry comparable to South Korea. I suspect that your keyboard is not working, and that's why you say the chip is not working.

If you wish, you can send me the chip to check what's wrong. I think it's just a simple issue with the pull-up resistors. I mean, does anyone here know for sure what the correct value for the resistors is? The CPC keyboard logic is very picky in this, sometimes it stops working if I make an angry face ...
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 11:20, 19 February 22
Well... If the IC do not works, he can ask to be replaced. (it is wrote 2 years warranty)
Now, I will not take the defense of sites selling circuits 5 to 10 times the price they buy them.
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: eto on 12:07, 19 February 22
Quote from: TotO on 11:20, 19 February 22Now, I will not take the defense of sites selling circuits 5 to 10 times the price they buy them.

Is there any other place where you can buy them for less than that? Even on Aliexpress I have to pay more than 20€ + shipping + taxes/customs. 

Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: TotO on 12:50, 19 February 22
Sure, they have increased their prices because retro-business stores have bought a lot of stock at very low price to sell them very high. They are not dumb, they do the same since.  :-\

I have sold the AY-3-8912 a lot a time at 1.90€ while Amigastore sold it over 10€.
It is not only related to this IC... In example, they sell the YM2149 close to 9€ when you can always buy it at 0.90€.

The same about Paula and other Amiga IC that was available at less than 5$ during years in China, before all those stores started to sold them over 20$. ;) 
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: willow3411 on 20:41, 19 February 22
Quote from: Nworc on 00:42, 19 February 22Excuse me, I cannot believe that this is a "bad copy". What I see on the photo is a genuine chip made by General Instruments, produced in Taiwan. Taiwan is not China, Taiwan has a high tech industry comparable to South Korea. I suspect that your keyboard is not working, and that's why you say the chip is not working.

If you wish, you can send me the chip to check what's wrong. I think it's just a simple issue with the pull-up resistors. I mean, does anyone here know for sure what the correct value for the resistors is? The CPC keyboard logic is very picky in this, sometimes it stops working if I make an angry face ...
Good evening,
you didn't read my post correctly!
I have an 8912 in Stock (a GI) with this one it works very well. and my keyboard has no problem.
In addition I mounted the resistance network 2.2K after and I tested with an 8912A (GI) and it works very well!
And two faulty ICs? I still have a doubt.
Title: Re: 6128 AY-3-8912A ? Works in CPC 6128 ?
Post by: SerErris on 03:36, 27 February 22
On The CPC464 the RN is close to the Keyboard Connector...

For the older revisions that is here, the small arrow marks the common pin (+5V)

You cannot view this attachment.

However for the cost down and medium sized mainboards for the 464 you would need to solder it directly onto the AY-3-8912A and bend up the common pin and connect it with a botch wire to Pin3.

So the AY-3-8912A is not that compatible with the new models of the 464, because they saved the RA solderpoints.
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