tanya@adds.newyork.NCR.COM (Tanya Katz) (11/10/89)
In article <12336@fluke.COM> Craig Johnson writes: >What exactly was screeching? This is terribly important to answering >your question. Possible sources are, the hard drive, the monitor, the >power supply, and the speaker. I'm going to guess it was the power >supply. Just to recap my opening remarks in <12324@adds.ncr.com>: >>On Sunday Morning, about 7:30 am, just after my husband complained >>that I left the computer on and it was "noisy," tfk, my home machine >>must have taken offense to his remark, because it started to emit >>a high pitched whine. As best I could determine, the screeching sounded like it was coming from the terminal itself. The unix-pc case was cool, especially around the disk and fan areas. The only keyboard response was to the first character to turn on the screen display. I couldn't shutdown and nothing else was being echoed by the driver. The screen display looked like garbage. >The scrambled display is indicative of a processor which has lost its >mind (due usually to misread opcodes), or a video memory which has >suffered a power hit. In either case, a sagging Vcc (5 volt supply) on >the motherboard will cause this kind of nonsense. I'm suspicious that >your power supply experienced a brownout, either because the AC main >had a problem or because the power supply itself is failing. Further, Brownout definitely crossed my mind. >If it ran in this mode very long, its possible that the power supply >overheated some of its components. I would be suspect of its long term >reliability. Now would be a good time to get a spare power supply from >Halted Specialties if you haven't already. [thanks Thad, I've got mine] Would you post or email me the address and/or phone number of this supplier? >Well, I could be all wrong about your problem Tanya, but this is at >least one good possibility. Thanks for the input. I am receptive to all possibilities. I have booted the machine several times since last Sunday, and it has been fine. But I'm cautious... -Tanya #-------------------------------------------------# | Tanya Katz (516) 231-5400 x430 | | | | ...uunet!ncrlnk!adds!tanya | | tanya.katz@adds.newyork.ncr.com | | | | ADDS Inc, 100 Marcus Blvd, Hauppauge, NY 11788 | #-------------------------------------------------#
wtm@neoucom.UUCP (Bill Mayhew) (11/13/89)
The screeching might might have been coming from the speaker, which is located in the back of the CRT housing. The speaker audio comes from the modem circuitry. I noticed on my 3b1 that there is a white ceramic Western Electric chip in an ersatz sort of socket (pins but no plastic surround) near where the volume control is on the motherboard. I believe that chip could be the trouble maker. I don't know about all 3b1/7300 motherboards, but that socket-like arrangement doesn't look real long on reliability. A cure might be to rock VERY gently under the chip with a screwdriver, lifting up a millimeter or so then reseating the chip, finally pressing down CAREFULLY with one's thumb. Extreme care is advisable with that chip since it is in a thin ceramic package and it is a custom part. On my own 3b1, the 68010 apparently lost contact in its socket. I experienced a crash a while back where the machine was totally functionless; pressing reset didn't generate the so-called lace pattern on the screen or anything. Removing and reseating the 68010 cured the problem. (This happened about 2 weeks after AT&T replaced the motherboard in my machine. Ironically, the original motherboard wasn't bad.) Its been about a year and a half since I reseated the 68010, and the machine is still running fine. Bill