A600 sound problem

[MSL]

Hi,

I just bought an Amiga 600 to play with in my vacation, but I have been a bit unlucky with it.

The power supply did not work, nothing happens when I plug it in, it does however give a high pitch sound, when you put your ear to it. I had an power supply for a A500 and that works, so it is not all bad, but it would be nice to have both working, anyone have any idea what could be wrong with it?

Second problem and the worst, the right sound channel is making some noise, even just on the boot screen. It is really random, sometimes with breaks of 30 seconds with no noise and then it starts again. I have tried different cables. I booted up something with music on, it played in both channels but right had a lower volume and with random noise on it. Any help to solve this would be greatly appreciated.

Cheers
Morten.

[skateblind]

Originally Posted by MSL

Hi,

I just bought an Amiga 600 to play with in my vacation, but I have been a bit unlucky with it.

The power supply did not work, nothing happens when I plug it in, it does however give a high pitch sound, when you put your ear to it. I had an power supply for a A500 and that works, so it is not all bad, but it would be nice to have both working, anyone have any idea what could be wrong with it?

Second problem and the worst, the right sound channel is making some noise, even just on the boot screen. It is really random, sometimes with breaks of 30 seconds with no noise and then it starts again. I have tried different cables. I booted up something with music on, it played in both channels but right had a lower volume and with random noise on it. Any help to solve this would be greatly appreciated.

Cheers
Morten.

Have you tried opening it and check the wiring? Are the connection points on the outside or inside rusted? Does the sound/noise change when you wiggle the inputs of the audio cable?

[PowerPie5000]

Best thing to do is check all the caps as the A600 is notorious for having leaky caps in it's old age this could be the problem with the audio (leaking capacitors around the audio circuitry?).

[MSL]

Hi, thank you very much for your replies.

I took it apart and checked all the capacitors and I found no leaks . The right channel is corroded abit, some of the metal is green. I wiggled the cables abit and gave the right channel a few spins and the noise disappeared (I played 3 levels of lemmings to test it ). I will see if I can get 2 new connectors at an electronic store, so it can be fixed properly.

Thank you very much for help.

Cheers
Morten.

Btw. on the parrallel connector inside the casing, there was this stranger sticker saying "Burn in", any idea what this means?

[PowerPie5000]

Originally Posted by MSL

Btw. on the parrallel connector inside the casing, there was this stranger sticker saying "Burn in", any idea what this means?

That sticker would usually have the word "pass" or "passed" on it. As far as i know it shows that the Amiga has completed a factory burn-in test - this is where it gets left on for a period of time to test stability and reliability of components by running some sort of stress test software. The sticker is nothing to worry about

[kipper2k]

Originally Posted by MSL

Hi, thank you very much for your replies.

I took it apart and checked all the capacitors and I found no leaks . The right channel is corroded abit, some of the metal is green. I wiggled the cables abit and gave the right channel a few spins and the noise disappeared (I played 3 levels of lemmings to test it ). I will see if I can get 2 new connectors at an electronic store, so it can be fixed properly.

Thank you very much for help.

Cheers
Morten.

Btw. on the parrallel connector inside the casing, there was this stranger sticker saying "Burn in", any idea what this means?

Don't just get 2 new connectors, the chances are when you wiggle the connectors you are slightly bending the board causing the 2 capacitors behind them to make a connection. I would strongly recommend changing the capacitors when you remove the connectors to replace them. Use isopropl Alcohol to clean the board once you remove them and reapply them to the board. These 2 capacitors are the worst on the board to change as they are in a very crowded area. Make sure you dont melt the keyboard plastic socket or you will be in a world of hurt.

(the Capacitors are aluminium 22 microfarad (uf), at least 10V, the voltage rating can go higher if you cant find a 10V rated capacitor

[Damion]

Originally Posted by kipper2k

Don't just get 2 new connectors, the chances are when you wiggle the connectors you are slightly bending the board causing the 2 capacitors behind them to make a connection. I would strongly recommend changing the capacitors when you remove the connectors to replace them.

Agreed... There is simply no way around it, the caps must be replaced. They are leaking even if you can't yet see it.

[MSL]

Hi, thank you for the replies.

I found this article about sound capacitors in Amigas that is interesting:

http://joj.home.texas.net/amigacap.html

He recommends using non-polarized capacitors for the output, since the output from the amplifier into the capasitor is in the range [-12, 12] v. The schematic in the article is for an A4000, I looked at a schematic for an A600, it has a similar layout as shown in the article.

[kipper2k]

Originally Posted by MSL

Hi, thank you for the replies.

I found this article about sound capacitors in Amigas that is interesting:

http://joj.home.texas.net/amigacap.html

He recommends using non-polarized capacitors for the output, since the output from the amplifier into the capasitor is in the range [-12, 12] v. The schematic in the article is for an A4000, I looked at a schematic for an A600, it has a similar layout as shown in the article.

Interesting article, one thing though. the A600 and A1200 is a multilayer board so drilling holes through the motherboard could do something nasty so a thorough check would have to be done before drilling and mounting a non polarised cap in its place

[rkauer]

No need to drill the board!

What I do when replacing caps on the Amiga is using ordinary pieces, cut the leads to 6~7mm and then make then in a circle shape to use as SMD devices.

And I strongly agree the use non-polarized units on the audio out circuit, but even common polarized units will work because of the very low current on the circuit. Just remember non-polarized units will last much longer.