13 Aug
2000
13 Aug
'00
5:26 a.m.
Tony Duell wrote:
Good news/bad news. Good news is that the 12v part of the system is work. Bad
news is that one of the 28F020's smoked.
Here is what I've been able to determine so far:
1) 5V section is fine.
2) -12V section has a major short (measured 0 ohms across it, not the
power supply).
3) The flash programming circuit has a problem.
4) The NIC seems to work as the hub now recognizes it but I haven't seen
what traffic is on it. Sniffer doesn't show a MAC address or anything.
But that may be the sniffer.
Conclusion/assumptions:
1) 5V is working, there for the main part of the mother board is unaffected.
2) Fails diags at LAN (7 error lights), may be SQE setting.
3) 28F020 fried but it's for D/L of image from tftp server.
4) -12v is only for RS232, there for short exists in that section.
Of course this is kind of weak right now.
BTW, the reason I asked the question here is that folks like us (real hackers)
tend to want to fix things and have the right kind of software/hardware
knowledge for this kind of stuff.
BTW(2), this is my $2 ebay find, a Nupon LTS-4 terminal server. When I fix it
I'll upgrade it to an 8 by adding the components. I should probably let it go
since I also have another terminal server on the way. But old electronics
shouldn't just be tossed in the trash, kind of feels wrong (yes I'm out of my
mind).
--
Linux Home Automation Neil Cherry ncherry(a)home.net
http://members.home.net/ncherry (Text only)
http://meltingpot.fortunecity.com/lightsey/52 (Graphics)
http://linuxha.sourceforge.net/ (SourceForge)
I need to double check a diagnostic I'm making. I have a board that fried
the a 1/2W ceramic resitor (in the -12V section of the PS). It also took
out a tant cap and the fuses for the +/- 12v (between the MB and the PS).
Are you sure it wasn't just that the tants shorted and took out the
resistor and fuses? I've had plenty of tantalum bead capacitors do that
over the years. I suspect the
RS232 driver chips but I need to know if the ethernet nic
(aui & bnc) use -12v. Anyone?
You're going to love this : Probably not, but it might do!
The thing is that the AUI port, and the internal 10base2 transceiver need
a 12V supply. But that supply can float with respect to the data lines
(which are transformer-isolated anyway) and with respect to local ground.