Testing AY Chip on the Toastrack

[tridy]

Hi.

When I was trying to solder an audio mod onto the AY chip, I managed to shorten some pins, and now even though I removed the short, I think this is the AY chip that is damaged and prevents the Toastrack from starting properly. It just shows the garbage on the screen. At some point I while testing I got it to work properly but as soon as I slightly pressed on the AY chip it went back to showing the garbage on the screen.

Is there a way to test the AY chip without swapping it for the new one? The real ones on eBay are quite expensive, and I would like to make sure that it is the AY chip that is the problem before I try to buy one.

Thanks!

[Moggy]

It will take someone smarter than myself to show how to test the AY chip in situ but I do know from experience that when the chip is shorted in some way the envelope generator is usually the first thing to break down.

The AY chip as I suspect you probably know, has apart from a "tone" generator, an envelope generator or "buzzer" as some like to call it that produces the saw tooth/triangular type wave forms and if this fails the chip may still play "tones" but not the envelopes usually used for bass notes so is something to be aware of.

[tridy]

Visually, it looks something like this through ZX-HD:

https://youtu.be/xRZkVUMxZV8

So to test it, it is more complicated with AY than just probing the voltages.

[1024MAK]

Be careful of the so called AY chips on eBay and other trading sites. There are a lot of fakes and remarked (relabelled) old chips around.

Actual new AY chips have not been made for many, many years. And the last ones to be made would have the Microchip name and logo on them anyway (that’s who bought the original semiconductor manufacturer).

Dare I say it, but if the machine worked once, are you absolutely sure that there are no short circuits that may be just touching, and no dry solder joints? It’s not very common for a damaged chip to work. They mostly permanently fail, either totally, or loosing one or more functions.

Mark

[Moggy]

Forgot to mention that I have a 2A which I robbed they AY chip out of for my Zonx module and replaced it with Zonx chip whose envelope generator had blown and it boots and runs ok and produces tones but no envelopes.

I know it's a different model of Spectrum but cannot see how a blown AY chip would be the sole cause of a Spectrum failing to boot.

[tridy]

An update. I have sent it for repair to ByteDelight. It appears I made a huge mistake but using some flux when I was soldering in the audio mod onto the AY chip. The flux got under the chip (I used alcohol to clean it after, but it was not enough as I see now) and shortened some of the traces corroded; corrosion ate up one of the traces. Here are the photos from Ben when he was repairing it.

After the trace was restored, it was up and running. The components survived the accident, and the AY chip went back to its place. I will get it back soon. A hard way to learn. I could have figured it out by myself if I removed the AY chip. However, I did not have another one to replace it with to test. I also did not know that you do not need to have an AY chip for the Toastrack to display the picture. If I knew that, I probably would have tried to desolder it. So, I learned several things. Still feel a bit disappointed in myself but oh, well.

[Moggy]

In my experience when the AY chip gets shorted out it can blow the envelope (buzzer) generator section of the chip whilst leaving the rest intact.
The chip will appear to work ok sounding the tones etc but will no longer sound the envelopes, the type usually used for the bass sounds, so it may be worth checking this when you get the computer back by playing an AY file that you know has a deep envelope generated bass element to it.