jmarsh wrote on 2024-05-19, 05:51:
It does sound like the chip is operating in the wrong mode, with one or more of the multi-function pins operating as outputs when they're intended to be input only. But that's probably just a symptom of VCC being almost shorted to GND; I'd say there's still more bad caps to be found.
Another possibility which is hopefully not the case here, but nevertheless shouldn't be disregarded: We just know that the printing on the chip says CS4216, and that it consumes more power than a properly working CS4216 is intended to consume on a properly working sound card. We do not know whether the chip actually is a CS4216, or the chip has a fake marking. Furthermore, even if it is the correct chip, maybe it is damaged.
If I'm unsure whether a chip might be fake, I like to plausibilize the chip by testing the ESD diodes in them: Use a meter in diode test mode, red lead to the appropriate ground connection, black lead to a signal pin. On many pins, you will get a reading betwenn 0.3 and .7 volts. Pins with similar functions should have the same drop-out voltage +/- a couple of millivolts. In case you don't get any reading for pin-to-ground, you can also try black lead to the appropriate Vcc connection and red lead to the pin. The key point of this procedure is to apply a "negative" voltage to the pin to make the ESD diodes conducting that will be non-conducting in normal operation. Different input structures (analog input, control input, data input, buffered output) usually have different characteristics, but like pins have very similar characteristics.
This method can also be applied to test soldering: On a typical ISA card with I/O ports, A4..A9 usually are connected to very similar logic structures, and measuring address-to-rail voltage drop at the ISA connector can show you whether some of the address bits is not making contact due to a bad joint. Similar ideas usually apply to all data pins, to the control pins /IOW,/IOR,/MEMW,/MEMR and so on. Especially in old cards with a lot of custom decoding logic, /IOW and /IOR might have different loads, so this is not a clear method, yet it helps getting started on where a problem might be.