Tracing the pins, the corrosion put a resistor between two pins of an op-amp. The only remaining problem was the milliamp scale, but that was a simple blown ... you’d fix a meter when you ...

That makes it a perfect tool for working with radios in the HF range. The project is relatively simple to construct, with an STM32F103C6 or C8 development board used as the brains of the operation.