Right, I had this board up earlier today. Voltages around Q4 and Q1 are exactly what I'd expect. However, the voltage across IC35 (LM324) is only 8.48V from what is supposed to be a filtered 12V supply. The filtering is done by R201 (100R), C148 (33nF) and C139 (supposed to be 47uF on the schematic, but only 10uF on my board - I don't know if it was always this value, or if it was a cock-up on my part when doing bulk re-capping).
So, it's dropping around 3.3V across R201 - which means a current draw of around 33mA, much higher than I would expect for a quiescent LM324. Is that filtered supply used by anything else ? Looks like I need to replace IC35 again and check what the voltages are when it's removed.
So, it's dropping around 3.3V across R201 - which means a current draw of around 33mA, much higher than I would expect for a quiescent LM324. Is that filtered supply used by anything else ? Looks like I need to replace IC35 again and check what the voltages are when it's removed.
Statistics: Posted by cjed — Wed Sep 17, 2025 11:43 pm