Atari 800XL with very faint sound

[Summer256]

Sorry if this is the wrong place but here are the details as best I can -

 

- I have an Atari 800XL bought from Ireland (typical Irish power is 230v 50hz).

- I am using in New Zealand (230/240 volts 50 hertz).

- It came with an old style power supply Pt. No. CO 61763-34. Big solid brick type that can't be opened. (from what I've been reading these are dangerous to use and unreliable). The power supply is rated at 240V~ 50Hz 24W OUTPUT 5V-7.5VA (made in UK)

- I've been using it without problem with a SIDE 2 flashcard multi-cart from Lotharek. (Which I only mention in case someone else has had issues with it)

- Recently the sound seems to almost disappeared. If I turn the volume right up on the TV I can still hear it, but it's very faint.

- I ran the self-test on the Atari and it detected no problems.

 

So my questions are -

- Is it possible the power supply damaged the sound chip just enough to give faint sound? (I'm pretty sure the answer to this is yes).

- If so, can someone recommend a good choice for a replacement power supply? (I don't need a lot of options, just something that works and is light-weight so I can save on shipping to NZ).

 

That's my main question. Although I'm also curious if anyone has both a Lotharek multi-cart and an Atarimax My IDE multi-cart and if they prefer one over the other. (I want to get an Atarimax card because I like their menu presentation better but I'm not sure if there are any other differences between the two cards).

 

Thanks for any help, assistance or advice anyone can offer.

 

I've just realized I have one more question - if the sound chip is damaged in someway, then where would I find a replacement?

 

Edited December 23, 2015 by Summer256

[Paul Westphal]

The power supply may be an issue, but if you look at the middle left of the motherboard, there is a very small chip usually marked "RCA" ...I foget the number. This amplifies sound. Replace it. Hopefully it is a socketed. It's a 6 pin chip, I believe.

[1050]

8 pins on U1 which is a LM358 op-amp, quite common and carried by just about everybody. Jameco, jdr, digikey and even eBay - search for LM358. A bit closer to you perhaps?

http://www.futurlec.com/Linear/LM358Npr.shtml

 

I don't think the power supply did a thing to the audio, but I don't know what actually did happen to it or why it's weak now. But the above chip is entirely responsible for audio output so it's a very likely candidate for outright replacement at this point. You might even remove it and put it back in and if the problem is dirty pins then this action might fix it completely.

 

What you have for a power supply right now sounds perfect to me. 5 volts with 1.5 maybe 2 amps for extra goodies to come in the future.

[_The Doctor__]

If you are worried about the power supply, measure the voltage with a meter... or use a scope to see how dirty it's ripple has become.... Dirty power can hurt things and cause seemingly random problem ... as for the op amp, we've seen them go bad or need cleaning and re-seating, very rare to see anything else go bad... clean and re-seat pokey as well if it's socketed

[Summer256]

Thanks all for the replies. I'm late getting back with a follow-up because I've also had problems with my main Windows computer. (Maybe the whole house is giving out a fluctuating voltage?)

 

It's been a while since I used a multi-meter but it looks like it's time to reacquainted.

 

I don't have a scope but I'm just going to keep replacing parts until I get it working again. Now that I've started to play the Atari again I don't think I can live without it.

[Kyle22]

If you don't have a scope, you can do it by ear. Get a non polar electrolytic capacitor as used in tweeters and crossovers. Put the cap in series with a small speaker as used in a 400/800.

 

touch that to your power supply. You should hear a pop sound, not a hum.

 

If you hear a hum, it means you have a shorted diode or an open capacitor in your power supply. Both are bad and must be fixed.

If you only hear a pop sound, and your supply is not over 5,2, then its good.

[Summer256]

Good news! I'm an idiot.

 

I tested it on another TV and it turns out it's my CRT that has dropped the sound. No wonder the symptoms of my fault were confusing to some people.

 

In my defense, I only had one TV that I was able to connect it with so I wasn't able to test it on another until now.

 

I have a Bang & Olfuson and must have messed with something on the service menu which killed the sound.

 

On the plus side, I've learned some things if the Atari power supply ever does fail me. Thanks for the advice everyone.

Edited December 26, 2015 by Summer256

[Summer256]

One final piece of information, left here just in case anyone has this problem and are looking for a couple of other steps to check -

 

I took apart the Bang & Olfusen and re-entered service mode, only to realize that volume is not one of the settings on service mode.

 

Further checking of every part finally revealed what the issue was - I had bent one of the SCART cable pins when pushing it back into the TV. So just the sound pin on the SCART plug was bent. That was the problem. I've straightened the pin and the issue has been resolved.

Edited January 1, 2016 by Summer256