Re: Dead A7V333 (maybe) - how do I tell ?


"ScottHW" <scotthwnet-ng@xxxxxxxxx> wrote in message
news:1151073516.632422.57370@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

snipe.........of excellent post by:
Roger Hamlett


Scott,

Roger made some good points but let's take it one step further to address
the one question you have - is it the mb or the CPU if it's not something
else..

One test is with a barebones system as I explained in my other post, and
using some coolant (freeze) spray. This would involve removing the heat
sink/fan off the CPU. With power off, cool the CPU chip with a few seconds
spray. Then apply power and see if you get any beeps. Obviously the
speaker must be known to be good and it's connected. Also (WARNING) do not
allow the power to be on for more than a few seconds - just long enough to
determine if it will beep or not. At this point you're not interested in
the beep pattern. One beep and shut it down or you run the risk (on some
CPU's) of frying them within a relative short time. Your's being an older
CPU, I would guess its in the 25-40 watt range and certianly won't fry as
quick as an 89w dual-core chip.

Using freeze spray is a time honored method for quick troubleshooting which
IC croaked on a board (I'm dating myself) but it's just as valid today to
see if a cold chip will contract enough to make an internal connection that
has separated by a micron or two. That is a common failure mode for IC's.
When you see something like a black glob on the board or smell something
acrid - that typically means the on-board power regulators shorted and took
some circuits with it and usually it makes a good boat anchor at that point.

You've not noted a "burnt smell" nor indicated seeing a BIOS screen - and no
beeps or other sounds. Test the speaker by putting the VOM leads across the
leads and see what the resistance reading is. I'm not sure what the
resistance of those speakers are but being nothing special, I would *guess*
8 ohms. Could be higher but you should get a reading and not just an open
circuit if the speaker is ok. Of course, disconnect the speaker from the mb
before testing. You should also hear an audible noise (scratching sound) as
you touch the leads to the speaker. The voltage from the VOM will cause the
voice coil to move and you'll hear - scratchy something if it's good.

After a few tries and nothing happening - and you're at the nothing to loose
point - then hit the CPU with the freeze spray until it frosts over or (and
this is the preferred method) remove the CPU, place it in a static free bag
and place that bag and chip into a zip-lock type bag to prevent
condensation, and put the whole thing in the freezer for a couple of hours.
The chip specs are published on the manufactures site and they probably say
the chip will operate to minus -40° F or close to that. Your freezer may be
cold but not that cold. After a couple of hours, put the CPU back in the
MB, hook up the heat-sink/fan and go for the gold.

Now if it fires up it should (potentially) boot to your floppy and run for
awhile - until it heats up again and quits. Then you'll know for sure it's
the CPU. If still nothing - the CPU is not out of the woods but most likely
it is the mb. With power on you could hit the power regulator chips, cap's
and other IC's on the mb with the freeze spray and everytime you cool a few
chips down, hit the reset button and see if it jumps to life. If it
does...... smile, you need a new mb...and still maybe a CPU depending on the
failure.

Radio Shack still carries the spray and I've seen it in auto stores also as
well. Again, this is a last ditch effort and you can cause damage just
doing this type of testing. It may get you closer to finding out if you
need both a mb and a CPU but in the end, do you really want to invest money
into that technology? A mb and CPU upgrade is not all that expensive for a
decent quality mb and a good CPU these days. Consider that you can purcahse
a new Dell for $399. But yse, I understand that if you don't have the coin,
you need to look at alternatives. That's why I'm making the suggestions
above.

You still have a few things to try but when you're satisfied it's dead meat
no matter what, you can do the final freeze spray tests or freezer bag thing
and either get a determination (CPU or mb) or maybe not.

There are a lot of way's to troubleshoot something and steps to follow.
Doing what you're doing now is correct - asking questions and taking it one
step at a time. My suggestions above are typically last ditch efforts for
the typical repair shop. Back in the days of bold.... this was a common
method when the board was dead and diags did nothing. Then we just replace
the last chip we froze when it started working and got on with the next
repair. Nice to know what caused the problem but chips do - just fail - and
if after a 24 hr burn-in (and some diag checks), the boards were certified
good to go. Got the soldering skills, IC tools and source for the chips? If
not and you want to learn - this would be a good one to start with....;-)

One final thought..........think www.NewEgg.com

Bob S.








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