stumpf@gtenmc.UUCP (Jon S. Stumpf) (02/08/90)
I have a power supply dead and no other means to verify other components are not affected as well. Visual inspection reveals only the power supply has problems. Power supply problems were confirmed with simple tests with a voltmeter. I am looking for suggestions to repair this machine. I will send it out to get fixed, buy new parts and do it myself, but I would prefer not to buy another PC and cannibalize. Thanks in advance. jss The gruesome story follows. My UNIX PC had been powered down for a month since I was going to be away and no one would be around to monitor it. Prior to my return, my father powered it up so I could do some uucp stuff. He said he came back after the initialization sequence, logged in, switch the phone to data and started some other things and walked away. When he returned five minutes later, he noticed the machine had tried to reboot and the disk was speeding up (as in accelerating) and winding down in a 5-10 second cycle. He powered it down, waited a few minutes, and powered it up again. It never got to the point to access the disk. When he reached back to power it off again, he noticed the top of the case (over the power supply) was hot. He said it would burn his hand if he left it on the plastic. So, extremely hot. Taking apart the machine and looking at various components, I noticed scorch marks on the power supply circuit board. Testing the components that had connections in the scorch marks revealed 8 out of 9 blue resistors (I don't do EE 8-/) and one capacitor out of commission. There is also a proverbial black box, a cube (actually), that I have no idea what it is or does or how to test it. It is sitting right next to the capacitor and shares a connection with it. I have a power strip with a line filter (big deal) and the various fuses at the power cord entry point on the PC were intact. If a component, or combination thereof, was drawing too much power and caused this problem, how do I prevent this from happening again? -- jss - Jon S. Stumpf
donlash@uncle.UUCP (Donald Lashomb) (02/12/90)
Geez, I hope not too much is fried in your machine - anything is possible, you might find that just putting in a new power supply is all you need -or- so much might be fried that it isn't worth fixing - I hope the former. Anyway, here's a source of 7300/3b1 power supplies: Halted Specialties Co. Santa Clara, Calf. 1-408-732-1573 or 1-415-969-1448 The power supplies are real inexpensive, too, like $10 -Don
chim@eceimg.ncsu.edu (Bill Chimiak) (02/13/90)
I had a similar experience when my fan failed. The plastic above my power supply was warped from the heat and the machine, from the log files' history, had rebooted numerous times. As recommended on the net, I replaced it with an AC fan. Since the day of the failure, I always make sure I feel air coming out of the back of the fan. What was interesting was that I discovered my fan HAD NOT FAILED! I placed it to a DC power source and it ran fine. About a couple months later, when I fired up my 3b1, I did not here my noisy AC fan come on. I pushed it with a cable tie and it started (just like a World War I airplane). So make sure the fan comes on when you start your 3b1. bill chimiak chim@mrips.bgsm.wfu.edu chim@eceimg.UUCP
twong@athena.mit.edu (Terry Wong) (02/14/90)
I'm interested in replacing the noisy fan on my 3B1 with a quieter one. I believe there was a thread during the summer on fan replacement, but I didn't save the articles. Can anyone give me what information they have. Recommendations, instructions? Thanks in advance. -------------------------------------------------------------------------- `Be yourself, no matter what they say' ---Sting