I recently found out that my 130XE outputs a low voltage level on its SIO port pin# 9 (Proceed). All my other Ataris have +5v on that pin (as expected) but my XE only outputs 3.26v. So I measured the voltage on pin 40 of the PIA chip and I found the same 3.26v there. I can not really make much out of this other than thinking about a possibility of a mulfunction on the PIA. The computer and the SIO port otherwise works fine without problems. Since Atari did not have any peripherals that actually use the Proceed pin I only found this out when testing my SIO2PC that I build which uses this signal.
With a 3.2v on pin 9, by the time this signal gets used in the SIO2PC, the voltage further drops to near 2v. this is not enough to register a HIGH logic level with the chip the signal connects to. The IC requires that an input voltage must be at least 3.5v when it's Vcc is driven at 4.5v. Had the 130XE output the correct voltage level, the SIO2PC would have worked fine (as it does with all my other Ataris).
My question is, do you think this voltage problem is related to the PIA chip being defective (even though other pins seem to work fine). I don't believe anything else on that trace is causing the problem as after it leaves pin 40 it goes directly to the SIO port pin 9, there is only one resistor and a capacitor on the way out. I haven't measured to see if the capacitor is leaking voltage to the Ground, could that be a possibility?
With a 3.2v on pin 9, by the time this signal gets used in the SIO2PC, the voltage further drops to near 2v. this is not enough to register a HIGH logic level with the chip the signal connects to. The IC requires that an input voltage must be at least 3.5v when it's Vcc is driven at 4.5v. Had the 130XE output the correct voltage level, the SIO2PC would have worked fine (as it does with all my other Ataris).
My question is, do you think this voltage problem is related to the PIA chip being defective (even though other pins seem to work fine). I don't believe anything else on that trace is causing the problem as after it leaves pin 40 it goes directly to the SIO port pin 9, there is only one resistor and a capacitor on the way out. I haven't measured to see if the capacitor is leaking voltage to the Ground, could that be a possibility?