Lynx 2 distorted sound help

[T7odd]

Another 7 years has passed so time to dig out the Lynx 2 again. I've just found this forum and am inspired to attempt to sort out an issue that it's had for a very long time. Many many years ago, I carelessly plugged the power cable into the headphone socket with power running through it. I realised as soon as it wouldn't turn on and put it in the correct port! Ever since, the speaker has sounded distorted and quieter than it once was.

 

I always assumed I'd fried a capacitor or something but the sound through the headphones is fine. I'm wondering whether to try changing the speaker or if it's likely to be a waste of time? It's a shame because otherwise it is pristine with the large soft case, carry strap and sun shield.

 

Thank you.

[unoclay]

my lynx speaker has the same issue, and may have been caused by the same accidental plugin issue.  Thoughts welcome.  I mostly play it with the headphone jack>stereo, but would be nice for the onboard speaker to sound better too....

[+Stephen Moss]

From the schematic, the audio goes through the headphone Jack to the input of U5 (an LM386 Amplifier), so the fact that sound via the headphone Jack is OK tells me that there is nothing wrong with the primary sound generation.

 

Although it is possible the problem lies with the speaker, as the audio is capacitively coupled to the speaker that should have blocked the DC thereby preventing damage to it so I would think it more likely that U5 was damaged. Unfortunately, without an Oscilloscope (which most do not have) the only way to know for sure is to buy another 16 ohm speaker and 220uF 6.3V Capacitor (C66, if the speaker has gone that has as well), disconnect the original speaker and connect the new cap and speaker between TP 11 (ideally pin 5 of U6) and Ground and if the sound is still rubbish then U5 should be changed as I think it more likely that has failed than the Bass boost feedback components C20 & R43.

 

Alternatively, as you need to purchase two of those three components anyway in order to identify the problem without an Oscilloscope, it maybe simpler to not bother with testing and just replace them all. 

[unoclay]

so, its more complex than "blow into it" ala old NES carts??

 

?