Move commands do not work on my classic LX200
Posted 02 February 2013 - 11:29 AM
I'm thinking there must be something unique in the hardware on one of the boards that specifically controls move commands. That is the only thing that makes sense for both the Keypad and TheSkyX to fail to execute a move.
Any assistance would be greatly appreciated. This is very strange indeed.
(Posting here and the LX200 Classic Forum to cover my bases)
Posted 02 February 2013 - 12:52 PM
Posted 02 February 2013 - 06:13 PM
Yea.... tracked it down to U11, a 74LS14. $0.67 from Digikey. The input is clearly shorted out. From the connector it's just a 4.7K pull up to +5 so it has to be in the IC. I am not sure exactly how it happened. I had my scope set up on the patio outside. There was some rain but I had everything covered very well. I'm guessing perhaps some water got into the connector. It was either dirty or residue created something wrong. Anyway the input got blown. Will verify when the parts arrive and I swap it out. I have a good soldering setup (Solder sucker, quality Weller iron, etc.) so it should not be a huge chore to swap out. It's interesting, I don't have an O-Scope (wish I did) but in ringing things out, I had my original Meade 18V (really about 22V) brick applied and I was appalled at the +5 internal supply. Just on my Fluke I could see it was oscillating between 3.9 and 4.9 so it has to have a terrible oscillation on it. I'd purchased a new, nice and clean, 15Vdc supply and with that hooked up +5 was nice, clean and stable. (At least as far as I can tell with just a DVM). Holy *BLEEP* those Meade bricks have to be the biggest POS power supply's I've ever seen. I'd heard they were bad but good grief. No wonder the regulator in there was heating like an oven. Hopefully nothing else went. As I said I can command things to work so I'm guessing the rest should be fine. I will have to check the pullup when I pull the ic out to be sure that leg of the ladder has not been blown too. If so I'll have to get a replacement for that too.