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robb robb is offline
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Default 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