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Death Watch Beetle on the motherboard?

 
 
Landmark
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      10-20-2007, 11:28 AM
Deathwatch Beetle on the motherboard?

I've got a problem with a PC that is really bugging me and I wondered
if anyone else had any ideas. Its an old machine that started off life
as a Compaq Deskpro but I'm not sure that there is any of the original
machine left in there these days.

Recently it has taken to "ticking" when I press the power on button.
The power led glows red and the ticking comes from the motherboard
speaker, evenly spaced at about two beats per second. After a period
of ticking it bleeps, the power led goes to the normal green, and then
it boots as normal with no problems whatsoever, and with everything
running cool to touch even when it is left running for days at a time.
This has been happening for several weeks so it doesn't appear to be
signalling imminent fialure.

The length of time it ticks for after power is applied is related to
how long it has been since it was last turned on. The longer the
machine has been turned off, the longer it seems to tick next time I
turn it on, almost like there is some sort of capacitor slowly
discharging while the machine is turned off. The ticking duration
ranges from zero seconds through to a couple of minutes. While it is
ticking, no power is being applied to the screen etc and pressing the
power and reset switches has no effect. I've tried keeping the machine
warm whilst it is powered off to see if it is a temperature related
problem, but the results have been inconclusive.

I've searched the net and quite a few people have reported the same
symptons but are ususally given answers like flaky hard drive, failing
psu, wires touching the fan etc. I'll emphasize that the ticking is
coming from the onboard speaker, it is not a mechanical rattle, and it
ticks at well defined precise intervals so it is not electrical noise.
The problem is not the disc drives. I have disconnected all drives and
the tick is quite independent of them. Likewise I removed the LAN card
and USB expansion card so it was only left with the motherboard and it
still ticks. I have also put in a different power supply unit (one
with way more power than the machine needs) and tried replacing the
processor fan and the motherboard CMOS battery, all to no effect. I've
also done all the normal things like check the seating of all the
components, check for scorch marks etc and not found anything
suspicious.

What I keep coming back to is that the ticking is generated by the
on-board speaker and sounds very deliberate rather than accidental, as
if it is the BIOS trying to indicate some sort of fault condition, but
it is not the bleep codes that are used to indicate permanent errors.
The bios screen lists the bios as:

AmiBios Hiflex setup utility version 1.30
DR742E BIOS Ver 1.00.18

Has anyone out there come across this type of ticking signal before
and are you able to shed any light on the meaning of it?

 
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Arno Wagner
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      10-20-2007, 02:52 PM
Previously Landmark <(E-Mail Removed)> wrote:
> Deathwatch Beetle on the motherboard?


> I've got a problem with a PC that is really bugging me and I wondered
> if anyone else had any ideas. Its an old machine that started off life
> as a Compaq Deskpro but I'm not sure that there is any of the original
> machine left in there these days.


> Recently it has taken to "ticking" when I press the power on button.
> The power led glows red and the ticking comes from the motherboard
> speaker, evenly spaced at about two beats per second. After a period
> of ticking it bleeps, the power led goes to the normal green, and then
> it boots as normal with no problems whatsoever, and with everything
> running cool to touch even when it is left running for days at a time.
> This has been happening for several weeks so it doesn't appear to be
> signalling imminent fialure.


> The length of time it ticks for after power is applied is related to
> how long it has been since it was last turned on. The longer the
> machine has been turned off, the longer it seems to tick next time I
> turn it on, almost like there is some sort of capacitor slowly
> discharging while the machine is turned off. The ticking duration
> ranges from zero seconds through to a couple of minutes. While it is
> ticking, no power is being applied to the screen etc and pressing the
> power and reset switches has no effect. I've tried keeping the machine
> warm whilst it is powered off to see if it is a temperature related
> problem, but the results have been inconclusive.


> I've searched the net and quite a few people have reported the same
> symptons but are ususally given answers like flaky hard drive, failing
> psu, wires touching the fan etc. I'll emphasize that the ticking is
> coming from the onboard speaker, it is not a mechanical rattle, and it
> ticks at well defined precise intervals so it is not electrical noise.
> The problem is not the disc drives. I have disconnected all drives and
> the tick is quite independent of them. Likewise I removed the LAN card
> and USB expansion card so it was only left with the motherboard and it
> still ticks. I have also put in a different power supply unit (one
> with way more power than the machine needs) and tried replacing the
> processor fan and the motherboard CMOS battery, all to no effect. I've
> also done all the normal things like check the seating of all the
> components, check for scorch marks etc and not found anything
> suspicious.


> What I keep coming back to is that the ticking is generated by the
> on-board speaker and sounds very deliberate rather than accidental, as
> if it is the BIOS trying to indicate some sort of fault condition, but
> it is not the bleep codes that are used to indicate permanent errors.
> The bios screen lists the bios as:


> AmiBios Hiflex setup utility version 1.30
> DR742E BIOS Ver 1.00.18


> Has anyone out there come across this type of ticking signal before
> and are you able to shed any light on the meaning of it?


The ticking may come in via power. When the speaker is powerd,
but by DC, every AC component on the DC is very audible.

The thing that it does depend on how long it has been off,
may not only be heat, but also leakage current in a capacitor.
This decreases with time under voltage. Capacitors age and yout
PSU has some in it that are under fairly high load and are
critical to PSU stability. So the ticking may well be comming
from your PSU.

Now the way to test this is usually with an oscilloscope.
You may also try a different PSU (could be difficult if this
is till AT-connector style). You could also hold headphones
to the +5V and +12V lines over a resistor of, say, 1k Ohm and
see whether you hear the ticking there.

If I am right, repair is by capacitor replacement or PSU
replacement.

Arno
 
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Landmark
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      10-21-2007, 02:35 AM
Arno Wagner <(E-Mail Removed)> wrote:

>So the ticking may well be comming
>from your PSU.


Thanks for the suggestion Arno but the ticking comes from the on-baord
speaker, not the PSU, and I have already tried swapping out the PSU to
eliminat ethat as the source of the problem. Also the ticking is
absolutely metronomic. If it was being caused directly by a capacitor
recharging or any form of electircla noise then I'd expect the tick
interval to be variable. I was hoping someone had come across this and
could identify it as some form of Bios indicator.
 
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Arno Wagner
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Posts: n/a
 
      10-21-2007, 01:46 PM
Previously Landmark <(E-Mail Removed)> wrote:
> Arno Wagner <(E-Mail Removed)> wrote:


>>So the ticking may well be comming
>>from your PSU.


> Thanks for the suggestion Arno but the ticking comes from the on-baord
> speaker,


I did not say the audible part comes from the PSU....

> not the PSU, and I have already tried swapping out the PSU to
> eliminat ethat as the source of the problem. Also the ticking is
> absolutely metronomic. If it was being caused directly by a capacitor
> recharging or any form of electircla noise then I'd expect the tick
> interval to be variable.


Not necessarily. A capacitor failure could cause somethine else
to tick that usually does not or has not enough impact.

> I was hoping someone had come across this and
> could identify it as some form of Bios indicator.


Ticking? No. There are beep-codes, but nobody uses ticking.

Arno
 
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