blown board snaffu, where to start ?
"legg" wrote in message
...
On Tue, 6 Nov 2007 07:25:01 -0500, "robb"
wrote:
this is the board where the 32 V line shorted with 5V line at
the
green ribbon connector near transformer and only blew center
busman fuse . i get continuity between 5v and 0V ref and now i
need some advice where to start looking for problems or some
methodology on what to do (pull ICs, etc)
and of course no schematic, i am trying to map the power
section
now
Pull connectors. Repeat 5-0V z test at both ends.
On the end with zero ohms:
- Is there anything that looks like a zener or crowbar across
the 5V
rail? Not likely, but check anyways. Disconnect them and repeat
z
test.
- Identify the 5V regulator, if present. Remove and repeat z
test.
- Apply 5V current-limited to 100-1000mA. Check mV appearing on
5V
tracking, looking for lowest values and finger components ( IC
and
caps ) for temperature rise.
Thanks for help RL,
i forgot to thank you earlier so tanks for that help.
i followed your advice to get to my current status.
looks like the ROM and 8031 MCU are sacrificial toast
thanks again,
rob
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