Dragon 64: No Sound - How to fix? [CLOSED]

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unumlapis
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Dragon 64: No Sound - How to fix? [CLOSED]

Post by unumlapis » Fri Jan 03, 2020 12:42 am

Noticed today that my D64 don't provide any audio output from the monitor port. What would be the most obvious to check and what would be the typical components (6821 PIA?) that could be bad?
Last edited by unumlapis on Sat Feb 08, 2020 9:57 am, edited 1 time in total.

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robcfg
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Re: Dragon 64: No Sound - How to fix?

Post by robcfg » Fri Jan 03, 2020 10:17 am

If there’s sound through the TV output, I’d try to trace back from the monitor socket and check every connection and solder joint in the way.

The monitor socket is on the PSU board, right? Check that the cable strip that attaches to the main board has connectivity on both sides and check the solder joints on both boards.

Also check on the monitor socket that there’s no short circuit and give it a good clean with contact cleaner.

sorchard
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Re: Dragon 64: No Sound - How to fix?

Post by sorchard » Sat Jan 04, 2020 12:40 pm

If there's nothing obvious in the connections then it's worth looking at the 4529 analogue mux first (IC6?). This is connected to the monitor and joystick ports with minimal protection and would be easy to damage. I've replaced one of these before to fix loss of audio. This component is obsolete but still fairly easy to get hold of.

There is also a 4050 buffer driving the DAC resistors, and both 6821 PIAs are involved in audio. I would trace with an oscilloscope to be sure before undertaking any major work.
Stew

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unumlapis
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Re: Dragon 64: No Sound - How to fix?

Post by unumlapis » Sat Jan 04, 2020 1:19 pm

@robcfg: Well, TV output isn't something that I can test since I don't have any TV around. But, I'll ask aroud might be someone who has an old TV. But, it's right that the monitor socket is on the PSU board and as well the ribbon cable is proper connected as well - well, I'll double check it just to make sure that it's not bad contact but I can't see how that could be.

@sochard: I'd looked at the schematics and init I'm thinking that it might be far fetched that any of the PIA's would be the cause and I could rather see that 4529 but didn't think about the 4050. Well, I just need to borrow a oscilloscope to be able to move forward.

Thanks for the input both, I'll keep you posted on the updates.

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unumlapis
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Re: Dragon 64: No Sound - How to fix? [CLOSED]

Post by unumlapis » Sat Feb 08, 2020 9:59 am

Long story short, it turned out that when verifying with another Dragon the conclusion was easy to make, it's my screens speakers which doesn't work... Also, after verifying connecting a laptop to the screen via HDMI resulted no audio. Case closed :D

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