Lynx 2 Sound Issue (Resolved)

[GadgetUK]

Hi,

 

Just another quick post here to help people that might run into similar issue to the one I found last week.

 

When fixing one of my two newly aquired Lynx 2's I found an issues related to the sound:-

 

Aweful sound quality from main speaker, very quiet even on full volume. I had already noticed a swollen capacitor when inspecting the board, it turned out from looking at the circuit diagram that it was related to the audio output circuit (used on the output part of the LM386 (U5) op amp). C11 - 220uF 6.3v had gone. After replacing this I noticed the sound wasnt much better and had very little volume. I put two and two together and came to the conclusion that someone had put power into the headphone socket, which had destroyed the cap and possibly damaged the speaker. I confirmed that the speaker was damaged by connecting the PCB up to a known working Lynx 2 speaker - the volume was 4 or 5 times louder and totally clear on max volume.

 

The 40mm speakers in the Lynx 2 are marked 16 ohm impedence with 0.2w I think, I couldnt find an exact replacement, but I did find a suitable 40mm 8 ohm, 0.25w speaker on EBAY. After having installed that the sound is perfect now, no distortions at max volume and it sounds just as loud as my other Lynx 2 with the proper official 16ohm speaker in it. For anyone with no sound, check the speaker, and check the components on the audio output logic. R23 (says 51 on the hand drawn circuit diagram)I think. Obviously check the speaker itself - if you've got no resistance across the coil its blown open circuit and it should measure the 16 / 8 ohm the speaker is marked with - NOTE this could read correct like mine did @ 16ohms but the speaker still the cause as the coil has heated up and moved / slipped when power was applied, or the cone itself distorted through the voltage application.

 

Also, you can check if you have perfect headphone audio out - as I did. That will provide a clue as to whether you've got a fault before the LM386 or afterwards. If you have perfect headphone audio but either no sound from speaker or poor sound from speaker then its likely to be a combination of the speaker itself, C11, possibly R23 and remotely possible it could be the headphone socket itself which disables speaker when headphones plugged in.

Edited April 5, 2012 by GadgetUK

[Zogging Hell]

I've done this (why did Atari make the speaker socket the same size as the power one and right next to it?) so thanks will have to try and fix this using your tips! It's been quiet for years and I thought I'd damaged something more sensitive than the speaker..

[GadgetUK]

I've done this (why did Atari make the speaker socket the same size as the power one and right next to it?) so thanks will have to try and fix this using your tips! It's been quiet for years and I thought I'd damaged something more sensitive than the speaker..

 

Yes, I was surprised that the speaker was at fault as well, and had assume that maybe the LM386 operational amplifier chip had been damaged. I think the speaker coil gets so hot that it damages the coil assembly, or it shifts because of adhesives heating up whilst the power is applied, or possibly the cone gets distorted from the heat or something...

 

Mine was very quiet, and with volume on max the sound was distorted - like when you try and put 100 watts of audio output into a 10w speaker.

 

On a similar note I wonder if its possible to mod the circtuit and add a 2nd speaker for stereo - obviously I would have to decouple the current audio as L & R mixed through the speaker I think... I might have a go at that, once ive worked out where a speaker could be mounted (if anywhere...)

Edited April 14, 2012 by GadgetUK

[+karri]

The speaker gets fried when you connect a power cord to the headphone socket. It just cannot take the DC current and it breaks.

 

--

Done that

karri

[ewesselman]

Hi Guys,

Thanks for this. Truly helpfull. Any experience with using the speaker of an old not working Lynx Type 1 as a replacement?

I am thinking about replacing the one in the Lynx Type 2 with a Type 1 speaker.