[lxdude]

The lens darkens in steps as you turn it down. According to the manual, there are two CdS cells. I assume they would both have to be broken to have no response.

Does anybody know where there may be a service manual or repair manual available? It's not obvious how to get to the meter area and I don't want to end up with a pile of parts and me no longer remembering where they go.

Those are silicon blue cells. They have a small transistorized amplifying circuit. The cells and circuitry tend to be very reliable. It's far more likely to be corroded battery contacts or a corroded wire leading from them, or a bad meter switch. Possible also is the ASA dial mentioned earlier. Working it through its range might help if the problem is corrosion.

Try it at different ASA settings and work the meter switch some and see if that clears it up. BTW, a CLA on that camera is not terribly expensive.