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General Category => Amstrad CPC hardware => Topic started by: Velktron on 18:33, 16 August 15

Title: Back after 2 years....CPC still mute.
Post by: Velktron on 18:33, 16 August 15
Hi, and forgive my long absence. I had just popped out on the forums out of the blue with this problem (http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/new-guy-'new'-mute-6128-and-a-broken-keyboard/) 2 years ago (a CPC6128 with no sound output, and a faulty keyboard matrix).

I really didn't work on it since, since I had a lot of other stuff on my mind, however I decided to give it another shot now that I had some free vacation time. So, I assembled a RGB SCART lead for it (how I found a 6-pin DIN connector is another story), and powered it on. Yup, colors were perfect, but the same problems of 2 years ago were still there (well, what did I expect?  ::) ): no sound and a whole set of keys (those mapped to X-matrix line 5 or AY pin 11) were non-functional.

In addition, the only joystick input not functioning was the "right" input...which also was mapped to, surprise-surprise, AY's pin 11.  :D

Well, now I was more thorough with my tests, even measured current and voltages to the very pins of the AY chip. All keys caused about 20 uA current to the chip when pressed, all caused a minimal voltage drop from the "5V pull-up high", all connections to and from the AY chip were fine, no broken traces on the PCB (as I had suspected initially,no idea what made me think that in the first place).

So it really must be a faulty AY chip. Probably I'm in the same boat as this guy (http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/hardware-problem-with-464-ay-chip-fault/), huh?

Some other interesting symptoms: no sound at all, and even the background "thinking noise" (http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/cpc464-designed-background-noise/) is gone from the speaker. I only get white noise if I crank it up. Plugged-in earphones also remain dead-silent.

A more interesting question is what could have caused such damage to the AY chip: maybe someone before me tried plugging in something that he shouldn't? Especially  the DB-9 joystick port looks a lot like a RS-232 or Famiclone controller input, and most of the pins go straight to the AY without any resistors or buffer stage in the mid  :o


Or tried to use the headphone port as an audio, or worse, a power input?  ::)
Title: Re: Back after 2 years....CPC still mute.
Post by: Bryce on 22:27, 16 August 15
Welcome back Velktron,
     the AY is the most "fragile" IC in the CPC. They don't need a lot of convincing to suddenly die. It also doesn't need to be anything obvious or extreme. The fact that they are fragile AND connected to pins that make it to the outside world (Joystick port) and the fact that they are mixed signal (analogue and digital in on IC) make them prime candidates for dying unfortunately. Luckily they are still relatively easy to find. Just remove the old one, install a socket and a new AY and you're done.

Bryce.
Title: Re: Back after 2 years....CPC still mute.
Post by: Velktron on 22:48, 16 August 15
The problem is now finding a donor...obviously, if I could find another working Amstrad CPC or even a Speccy +2 I wouldn't cannibalize it. I have a working Atari ST which has a similar chip (the YM2149F) but which ofc I have no will to cannibalize and adapt to the CPC, assuming that it's even possible.

My hope now is that I can find some sort of cheap toy (e.g. an old electronic keyboard or broken console) which contains a discrete AY chip (not an FM chip or a binary blob). Ordering one online is probably gonna cost more than I paid for the entire CPC (well....hard to beat at 5 Eur, even if it didn't include its monitor or any disks ;) )
Title: Re: Back after 2 years....CPC still mute.
Post by: Bryce on 22:54, 16 August 15
?? You can still buy the chip all over the place. I have a box of them here. Send me a PM if you want one.

Bryce.

Edit: If you have access to any scrap Arcade machines. Many of the old 80's / 90's "one armed bandits" had sound PCBs with an AY on it.
Title: Re: Back after 2 years....CPC still mute.
Post by: Velktron on 00:14, 17 August 15
Well, that's a nice offer, but if your location is really Sao Tome and Principe, shipping costs may be through the roof. I'll really need to think about it.

As for scrap arcades....I think most of them (scrap or not, regardless of age) were sold out and exported out of the country after the infamous Law 3037/2002 (https://en.wikipedia.org/wiki/Law_3037/2002) took place. That one pretty much killed traditional arcade rooms in Greece, and left only a fraction of them behind, whereas before there was a flourishing resale and servicing industry revolving around them. I'm glad I was able to live the golden arcade years of the 80s and 90s before that travesty hit...
Title: Re: Back after 2 years....CPC still mute.
Post by: Bryce on 00:45, 17 August 15
No, I'm not in Sao Tome, I just like to choose exotic flags. I swap it every few months :)

I'm in Germany :)

You should be able to find one on ebay for under €10 though.

Bryce.
Title: Re: Back after 2 years....CPC still mute.
Post by: EgoTrip on 00:53, 17 August 15
I wonder if there are any CPC's on Sao Tome
Title: Re: Back after 2 years....CPC still mute.
Post by: pelrun on 06:39, 17 August 15
the AY is the most "fragile" IC in the CPC. They don't need a lot of convincing to suddenly die.


Killed mine as a kid through static discharge by touching the screen whilst holding the joystick. Parents were not pleased.

Title: Re: Back after 2 years....CPC still mute.
Post by: Bryce on 10:45, 17 August 15

Killed mine as a kid through static discharge by touching the screen whilst holding the joystick. Parents were not pleased.

Yup, that's enough to do it if you are unlucky.

Sao tome: I very much doubt that there's a CPC there. Do they even have a permanent power grid there?

Bryce.
Title: Re: Back after 2 years....CPC still mute.
Post by: steve on 15:59, 17 August 15
Not long ago the results of Google analytics or something were posted here, I can't find it now but it showed the number of people accessing the wiki and the country they were in, perhaps Sao Tome was listed there.
Maybe Gryzor can tell us.
Title: Re: Back after 2 years....CPC still mute.
Post by: Bryce on 16:16, 17 August 15
I very much doubt that anyone in Sao tome is browsing our Wiki: Telecommunications in São Tomé and Príncipe - Wikipedia, the free (https://en.wikipedia.org/wiki/Telecommunications_in_S%C3%A3o_Tom%C3%A9_and_Pr%C3%ADncipe)

Internet: "available, dial-up low quality, "broad band" (128/256) very expensive"

Bryce.
Title: Re: Back after 2 years....CPC still mute.
Post by: Gryzor on 19:50, 17 August 15
Since the beginning of the year, no hits were registered from Sao Tome. Bummer.



Title: Re: Back after 2 years....CPC still mute.
Post by: CraigsBar on 01:43, 18 August 15
We need to go on a cpcwiki trip to ”fix” that. On wait I bet bora bora has had no hits either, and I personally would rather go there!
Title: Re: Back after 2 years....CPC still mute.
Post by: Bryce on 15:31, 18 August 15
We need to go on a cpcwiki trip to ”fix” that. On wait I bet bora bora has had no hits either, and I personally would rather go there!

Well if you get to go to Bora Bora then I'm coming too!

Bryce.
Title: Re: Back after 2 years....CPC still mute.
Post by: Gryzor on 19:57, 18 August 15
Will the natives cook us alive or accept the CPC as their new god?
Title: Re: Back after 2 years....CPC still mute.
Post by: TFM on 21:43, 18 August 15
I very much doubt that anyone in Sao tome is browsing our Wiki: Telecommunications in São Tomé and Príncipe - Wikipedia, the free (https://en.wikipedia.org/wiki/Telecommunications_in_S%C3%A3o_Tom%C3%A9_and_Pr%C3%ADncipe)

Internet: "available, dial-up low quality, "broad band" (128/256) very expensive"

Bryce.


OMG! This data is over 15 years old. That happens if you refer to Wikipedia!  :P :P :P




Uups! Doh!!! This is a Wiki here too! Sh...!
 :-X :-X :-X :-X :-X :-X :-X :-X :-X
Title: Re: Back after 2 years....CPC still mute.
Post by: Bryce on 22:32, 18 August 15
Yes, they have better internet now, but it's all satellite for the downstream as far as I can see and I doubt it's cheap.

Bryce.
Title: Re: Back after 2 years....CPC still mute.
Post by: TFM on 23:53, 18 August 15
Yes, they have better internet now, but it's all satellite for the downstream as far as I can see and I doubt it's cheap.

Bryce.


Well, you must know it - living there.  :laugh: