9810 Power Problem? - Printable Version +- HP Forums (https://archived.hpcalc.org/museumforum) +-- Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum-1.html) +--- Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum-2.html) +--- Thread: 9810 Power Problem? (/thread-41408.html) |
9810 Power Problem? - Katie - 08-27-2003 My 9810 has gotten flaky. The problem seems to be somewhere in the power supply circuit. There seems to be some sort of power-is-good-boot-the-CPU function in the calc because after you turn it on, it normally takes a few seconds before it comes to life. Recently my machine isn't getting this "boot" signal as it should, I think. Sometimes it does work, but then goes dead after a minute or two. Other times it just sits there with all LED's off or some of them on but with no keyboard response. But the fan always works and all 5 marked power supplies (+12, -12, +16, +20, +24) measure good and are clean (no noise). Does anyone have any experience with this or any idea about where this supposed boot-up circuit might be located in the 9810? Thanks,
Katie
Re: 9810 Power Problem? - Tony Duell - 08-27-2003 There is a power-on reset circuit, which pre-loads all the microcode PC flip-flops with 1's to start the CPU at the right point. Re: 9810 Power Problem? - Achim Buerger - 08-27-2003 Katie,
Good look, Re: 9810 Power Problem? - Katie - 08-27-2003 Thank you both for that great information. I'll check out the monostable circuit that you described, Tony, to see if it's working correctly. If that's not the problem I'll try the cold spray technique, Achim. Just one question for either (both of you)? How did you get access to the boards while the machine is running? Do you use card extenders? If so, how to you get to the boards in the stack positioned in front of the fan? Right angle extenders? HP must have made a special test jig for servicing these machines. Of course all that the field techs would do would be board swapping, but what did the real service techs use?
-Katie
Re: 9810 Power Problem? - Achim Buerger - 08-28-2003 Hi Katie, To access the boards in the memory cage is principically the same, but for some boards you need one more bus extender with 2*10 contacts. By using ribbon cable which is long enough you can bend it out of the card cage and lay the card under test on top of the calculator. Achim
Re: 9810 Power Problem? - Tony Duell - 08-28-2003 Firstly a couple of points from your first message. The fan doesn't tell you a lot -- it's an AC fan running off the mains side of the transformer (in you case (120V), straight off the mains, in my case (240V), the mains transformer primary acts as an autotransformer). Secondly, you say you tested the 5 labelled PSU rails, but presumably you didn't test the 5V line (which is, of course, the supply for all the logic). There's a convenient capacitor to use for this on the display PCB (I think the ends are even marked!), or you Re: 9810 Power Problem? - Katie - 08-29-2003 Wow Tony, where do you find the time to do all this hacking? I don't know if I'd have the patience to do the the kind of debugging that you do with your Logic Dart and wires soldered to the boards. I really need to use the board extender approach so that I can move from circuit to circuit quickly. I also have a really hard time working on these large machines without schematics. It's one thing to fix the handheld HP's with 2 to 12 chips blindly, but the 9810 is impossible. I tried repairing a dead Wang 520 without a diagram and got nowhere. Luckily I found someone with a full set of schematics and it was a relative breeze with them. [The Wang 500 design seems a lot more straightforward to me than the 9810, but the Wang is a simpler machine.]
BTW, I forgot to mention that the 5V supply looks pretty clean in my 9810 so I figured that wasn't the problem.
Re: 9810 Power Problem? - Achim Buerger - 08-29-2003 Katie, Re: 9810 Power Problem? - Katie - 08-29-2003 Achim, Thanks for that pointer! I'm printing it out now. It'll make for some wonderful bedtime reading :) -Katie
Re: 9810 Power Problem? - David Smith - 08-29-2003 Don't you already have a set of 9810 schematics... your friend in Texas...
Re: 9810 Power Problem? - Tony Duell - 08-29-2003 The HP Patents for the 98x0 series are a wonderful resource, but do be careful. I've found differences between the schematics in the patent and production machines (the memory system in my 9830 is _totally_ different to that in patent GB144141). Re: 9810 Power Problem? - Tony Duell - 08-29-2003 Actually, I generally have a pretty good idea as to the problem area from testing on pins I can reach with the machine fully assembled. I then pull the probably bad card and solder up to 10 wires on it (I can't find more than 10 different colours of wire easily :-)). I then probe those. It rarely takes more than 2 attempts at soldering on 10 ways to find the bad chip. Re: 9810 Power Problem? - Katie - 08-30-2003 Oh my, I completely forgot about those! Thank you, thank you. They are much more readable than the fragments in the patent. However, the patent makes a nice complement to the schematic in that it explains the detail that's not noted on the drawings.
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