Boebert@HI-MULTICS.ARPA (10/15/86)
My ][+ has the following hard memory failure: at locations 8000 and above, the monitor commands *8000: 00 00 00 00 00 *8000.8004 results in a display of 40 40 40 40 40 and similarly for other entered values (i.e., 01 -> 41, etc.). This failure was traced from its original symptom, failure to boot (obviously owing to the relocation failures at high memory). Failure occurs with all slots empty; the machine also has a new power supply. So, for all you ][+ hardware wizards out there: what chips do I replace to fix this? Thanks, Earl (Boebert @ HI-Multics)
binder@asd.DEC.COM ("Exit, pursued by a bear") (10/16/86)
Boebert@hi-multics.arpa writes: > My ][+ has the following hard memory failure: at locations 8000 and > above, the monitor commands > > *8000: 00 00 00 00 00 > > *8000.8004 > > results in a display of > > 40 40 40 40 40 > > and similarly for other entered values (i.e., 01 -> 41, etc.). The failing chip may be one of three. Take the cover off your Apple and look at the RAM area, which is enclosed in a big white box toward the left side of the motherboard. At the left end, in IC locations C1, D1, and E1, are three 14-pin configuration jumper blocks. Pin 1 is at the lower right corner, and the pin layout is like this: +-----+ 8 =| |= 7 9 =| |= 6 10 =| |= 5 11 =| |= 4 12 =| |= 3 13 =| |= 2 14 =| o|= 1 +-----+ Look at pin 8 of any one of these jumper blocks (they should all be the same), and see what other pin it's connected to. If pin 8 is connected to pin 14, then the failing chip is in location C9. If 8 is connected to 13, the failure is at D9. If 8 is connected to 12, the failure is at E9. (I've assumed you have 48K. If not, then you have 36K, and you should look at pin 7 instead of 8 in the preceding description.) Before assuming that you have a bad chip, try reseating the chip in its socket in case the problem is merely poor contact. If that fails, try swapping the suspected chip with the one to its immediate right (C10, D10, or E10) and see if the monitor reports that $00 has become $80. If so, you have a bad chip. *** Do all this reseating and chip swapping with power OFF! *** Cheers, Dick Binder (The Stainless Steel Rat) DEC Enet: ASD::BINDER UUCP: { decvax, allegra, ucbvax... }!decwrl!asd.dec.com!binder ARPA: binder%asd.DEC@decwrl.ARPA
sdh@joevax.UUCP (The Doctor) (10/16/86)
> My ][+ has the following hard memory failure: at locations 8000 and > above, the monitor commands > > *8000: 00 00 00 00 00 > > *8000.8004 > > results in a display of > > 40 40 40 40 40 > This means that the seventh bit is being set all the time. One of your ram chips is bad. Here's one way to fix the problem: run a ram test on it. If your local Apple dealer wants to keep you as a customer, they should be more than willing to give you a copy of the apple approved ram test program, or borrow an Integer Basic firmare card, since it contains a ram test on board. Either should tell you which 4116 is bad. Your other alternative: go to Radio Shack and buy 1 4116 ram chip. Locate the bank of 4116's on the motherboard. The row closest to the slots will contain the last 16k of ram --that's where your problem is. I don't know which of the chips is the bad one, but just use the process of elimination to find the bad chip. Most likely, it will be either the 2nd from the left or the 2nd from the right in that row. NOTE: always make sure the power is off before you swap chips, and beware of static elctricity. You may want to spread aluminium foil on the table under your apple, as that will help deter static charges. A side note, there are times when a bad ram chip will work just fine when swapped with another chip. I've done this before: found a bad chip, and swapped it with its neighbor, and removed the problem, but for piece of mind, you should use a new chip as the replacement. The reaseon why you can't boot your disk is that DOS is loaded in the last 16k of ram. Since your ram failure is there, every byte of dos is getting OR'ed with $40, thus making DOS invalid. Steve Hawley joevax!sdh
Thomka.OsbuSouth@XEROX.COM (10/16/86)
Replace the 16K (generic # 4116) RAM at location E9. Chuck PS. Here are additional locations for other failures Locations 0-3FFFH 01=C3 02=C4 04=C5 08=C6 10=C7 20=C8 40=C9 80=C10 Locations 4000-7FFFH 01=D3 02=D4 04=D5 08=D6 10=D7 20=D8 40=D9 80=D10 Locations 8000-BFFFH 01=E3 02=E4 04=E5 08=E6 10=E7 20=E8 40=E9 80=E10