- Added two-way switch running a wire off of pin 9 of MC1733 to pin 3 of RGB connector to give me both monochrome and color composite at a flick of a switch.
- There's a whole thread of why -- US models don't give color-composite on pin 1 of RGB for some reason.
- I recently double checked all connection and the solder joints are good, no shorts and the switch is new.
- Also, I never flip the switch until power is off to both the computer and the monitor -- very careful about that
- Hermes chip
- had that since the 90's
So here's what happens, after a short period of time the picture goes away (no signal). If I reboot (either side switch or remove power) I get nothing, no picture and the computer won't boot since F1 or F2 don't spin up the microdrive. I do get a power led (yellow) but that's it. The Hermes gives keyboard audio feedback but after about 8 or 10 key-presses it also stops accepting them. If I leave it off for a while things come back to normal. At present the video switch is set to normal (i.e. the mod is turned off and I'm only getting monochrome-composite from pin 3 / 2).
It happened last night after the machine only being turned on for 10 minutes total and it took about 30 minutes to come back after I powered it down (completely unplugged both QL and monitor). It just happened today, again after being on a short time. This time I immediately opened up the case (maybe 5 minutes between next power up) and the video picture came back immediately. I then proceeded to poke around, pressing on chips and wiggling connectors (including the mod wires and switch) and nothing, the picture is solidly in F1 monochrome mode and has not left me (been on now for a few hours).
Any idea what to look at? I checked the power on the brick and it gives 15 volts AC and about 10 - 11 volts on the DC line, which is a bit high but it's not under load. Should check it now that I have it open. I assumed somehow I damaged the MC1733 chip with my mod but it is working presently and also, I'm bypassing the mod to be back to factory normal. I also thought maybe the ZX8301 but again, picture signal is working perfectly now.
So that's why I'm calling it a glitch since it isn't as repeatable. But what causes no video signal and no boot up on in a QL? What should I be looking at?
I do have replacements for the ZX8301 and the MC1733 but if my mod is causing it then I'd rather not blow a second and I'd like to keep the mod if possible (plus my ZX8301 is wired with diodes like a Christmas tree so that will take a bit of work to swap out). All I'm doing is grabbing color composite off of pin 9 of the MC1733 and ground pin 2 off of the RGB connector so that shouldn't damage the chip right (assuming I didn't do something bonehead like short connections -- again, double checked that I didn't)? And I added a 47 ohm resistor from pin 9 to help the color image.