Thank you! Incidentally, the Pentax K1000 is the only other Pentax with the same type of "light switch" as I call it. The stop-down lever should be the same as the ES and ES II models.
Many people got confused with that lever, including me when I first got one. I was used to the SP and SP II and had a couple of rolls badly exposed because I was flicking the switch up whit the SMCT lenses. Didn't read the manual until it was too late!
Thanks for the replies all. I've got it topless (ooer) at home at the moment for a good clean and I'm going to test and adjust the two metering circuits at the same time. I guess I can setup a properly metered scene at EV 8 or 12 or something and adjust the spotmatic from there, both stopdown and open aperture metering.
I retrieved my SMC 28mm and, fiddling with the two variable resistors at EV16 and EV8 I've gotten the open aperture metering circuit well inside what I'd regard as acceptable readings compared to my sekonic and checked against my F100 with the same lens fitted via an adapter. Not too much adjustment needed either, which suggests that the two CDS cells (or whatever is in the spotmatic) are ok.
The difficulty is with the stop down metering. Even adjusting the seperate variable resistor for the stop down metering to its extreme I cannot get the stop down metering to read at anything other than about 2 stops underexposed. This has me confused because it's the simpler of the two circuits, and it's reading off the same two CDS cells which appear to be just fine. Anyone suggest any possible avenues of investigation ?
Interesting (by which I mean annoying) side note, you have to put the top back on the spottie to actually get the meter to read correctly. That led to some perplexed fiddling and weird erroneous readings until I worked it out :confused:
Unscrew the lens 1 turn (to uncouple the aperture coupling) and adjust the stopdown metering to be accurate. I'm pretty sure this stopdown metering is only supposed to be accurate with old lenses.
Don't forget to keep the eyepiece covered when metering, the cells can see through there...
If you find that you can get it to work easily along this line of reasoning... Then I suspect that's what the balance control is for.
OK so it sounds like a bit of a problem.
To rule out angle of view differences, you could try both with the 28mm - unscrew it (and set the lens switch to Manual) so you use the same lens to do both tests...
For what it's worth, when I tried this Full aperture metering gives two stops overexposure, and Stopdown metering gives one stop overexposure on mine, compared to Sekonic spotmeter...