68kMLA Classic Interface
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| Click here to select a new forum. | | LC475 with no sound output | Posted by: shirsch on 2025-05-14 07:14:49
I think I need a bit of help in troubleshooting my LC475. I'm scratching my head a bit over the schematic on page 13. A scope on pins 18 (or 19) of the DFAC chip shows that PWM is being generated when I trigger a notification. It reads a steady square wave under quiet conditions that then "shakes" a bit at system beep. But there is nothing appearing at the SPKR +/- pins on the sound chip. What's confusing me is that there appears to be a second signal path through a pair of DAC stages (TLE2062 op-amp). At first glance this appears to be for headphones only (?) but I'm not seeing any activity at the headphone jack either.
Would appreciate any insight into the circuit function and any troubleshooting hints that folks might have to offer. | Posted by: shirsch on 2025-05-15 15:17:49
FIXED: Problem was a rotted -5V contact on the power supply molex plug. Looked fine from the outside and measured continuity when a test lead was stuck in... Simple, but ran me around in circles for a bit. | | 1 |
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