rich@lakesys.UUCP (Rich Dankert) (05/16/88)
[]
I have a question for other users of the net that have been
servicing and or have run into this problem.
I have a 130 XE machine, that will not allow one to do
anything except watch the RAM test in the self help
diag's text. It goes there right off. Once in a while one
can press RESET and get the machine to Basic, but after
hitting Return, major Lock-up.
Have tried the OS chip, wish another, and even my Omni view,
along with the Antic, the Salley and MMU (6161) all to no
avail. These seemed to be the place to start, but all yeild
the same problem. I was going to try the PIA chip, but think that
this would yeild the same, and really don't like de-soldering
40 pin chips. I can think of more pleasent things to do ;^)
Any help would be appreciated, as this one has me scratching
my head.
BTW. All is the same EVEN with the Keyboard not connected
rich.....
UUCP: {Ihnp4,uwvax}!uwmcsd1!lakesys!rich
--
Disclaimer: The words, expressions posted here are my own.....
Nothing is ever so bad that it can't be made worse by trying to fix it
-- Law of the Hackercfchiesa@bsu-cs.UUCP (Christopher Chiesa) (05/17/88)
In article <670@lakesys.UUCP>, rich@lakesys.UUCP (Rich Dankert) writes: > [] > I have a 130 XE machine, that will not allow one to do > anything except watch the RAM test in the self help > diag's text. It goes there right off. Once in a while one > can press RESET and get the machine to Basic, but after > hitting Return, major Lock-up. > > [list of attempted fixes deleted] Have you considered/checked the possibility that you have a bad 6502? I've seen that happen, although usually the thing just doesn't run, period. Could be just something subtle in that the reset line is getting tweaked when you don't want it to, in combination with something being wrong in the part of the CPU that automatically starts at such-and-such location in memory on powerup. Just a thought... -- UUCP: <backbones>!{iuvax,pur-ee,uunet}!bsu-cs!cfchiesa cfchiesa@bsu-cs.UUCP
jhs@MITRE-BEDFORD.ARPA (05/17/88)
> I have a 130 XE machine, that will not allow one to do > anything except watch the RAM test in the self help > diag's text. It goes there right off. Once in a while one > can press RESET and get the machine to Basic, but after > hitting Return, major Lock-up. Since the PIA is the chip that selects the self-test ROM, I would check the PIA first. Look at the logic line from the pin (I think it is Bit 7, the Most Significant Bit (MSB)) to see if it is asking for the diagnostic ROM (I think that would be a LOW output instead of +5 volts). Also check the logic chips that this bit controls. One of them may be burned out, causing it to command the diagnostic ROM into action even if the PIA is not telling it to. I suspect you will find the problem to be either a bad PIA or a bad gate driving the ROM chip select line. > Have tried the OS chip, wish another, and even my Omni view, > along with the Antic, the Salley and MMU (6161) all to no > avail. These seemed to be the place to start, but all yeild > the same problem. I was going to try the PIA chip, but think that > this would yeild the same, and really don't like de-soldering > 40 pin chips. I can think of more pleasent things to do ;^) Given the symptoms, the circuitry from the PIA to the O/S ROM is the probable location of the problem. Save all those parts you changed, 'cause they are probably perfectly good. Since you changed the MMU, I suspect it is, after all, a bad PIA chip. The only other thing I can think of is a short across the lines from the connector where the keyboard plugs in. Hah, that's eliminated by the fact that both OMNIVIEW and the Atari chip come up the same way. Since they react oppositely to the OPTION key, it can't be just a short that makes it look as if the OPTION key is being held down. > Any help would be appreciated, as this one has me scratching > my head. It would of course help if you had a 130XE schematic diagram and a 'scope or at least a VOM (Volt-Ohm-Milliameter). But the more I think about it, the more I think it is probably a bad PIA. Either that or a fault in the wiring to the PIA, like a solder splash that shorts a pin to ground. Good luck. -John Sangster / jhs@mitre-bedford.arpa
hans@umd5.umd.edu (Hans Breitenlohner) (05/21/88)
In article <670@lakesys.UUCP> rich@lakesys.UUCP (Rich Dankert) writes: >[] > > I have a 130 XE machine, that will not allow one to do > anything except watch the RAM test in the self help > diag's text. It goes there right off. Once in a while one > .... > Fixing small computers 101: (also applies to any other electronic equipment): Check the power supply. Make sure it puts out 5 volts and not much ripple. A scope is great for this, but a VOM will do. Actually this one does not sound like a power supply problem, but you never can tell for sure. And you always feel like kicking yourself when you discover, after much searching, that the solution was that simple. When doing a coldstart, one of the first things the XL/XE OS does is a quick memory test. If that fails, it dumps you into the memory diagnostics, and it sounds just like that is what is happening to you. The fact that you get that far indicates that, in all likelyhood, the cpu, antic, gtia, parts of the pia, and the rom are all working. The RAM must be working at least somewhat, since the memory test must use it for scratch storage, screen, etc. You did not indicate if the memory test seemed to be running, and how it thought that the RAM and ROM areas checked out. If you see some failures there, you should have some idea of what is broken. From the symptoms I strongly suspect that your problem is bad RAM. Assuming that RAM is your problem, the next step is to identify the bad IC. Unfortunately the diagnostics go to much detail identifying the 1k region containing the error, but neglect to identify the bit. If your display is somewhat garbeled, the pattern may help to identify the bad bit. If your memories are socketed, swap away (you have a set of spares right there). If your memories are soldered in, here is a trick I once used to fix just such a beast: take 3 memory chips, and bend their legs inward slightly, so that you can stack them on top of each other, and have them hold together tightly. Put this stack on top of a memory chip, and see if the problem goes away. If not, move it to the next one, and so on. Be sure to remove power whenever you are moving the chips, be careful not to short anything, and all usual precautions about handling static-sensitive components apply here, too. When I did this, it turned out that two memories were enough to "outvote" the bad one, but one was not enough. I wold use three in case your error is more persistent. I hope this helps!