[parisc-linux] Re: Apollo 9000 power problem

[parisc-linux] Re: Apollo 9000 power problem

[Christoph Plattner]

Hello HP Hackers !

I have a work around for the POWER SUPPLY Problem.

Using schematics and analysing this very very hard thing,
I found out, that the problem we all have was created
by an exploded capacitor.

The thing running out of the capacitor mixed with the dust
in the machine generates an resistor on the PCB board.

On the low voltage end of the power supply (near front),
ther is a small SIM-like module which does the supervision of
all volatage lines (plus over current protection) and which
generates the reset impuls.

Now to the problem. The line coming from the current measure
transformer is the neighbour line of the -12V line. Because
of the electrical resistor because of the dust, etc, the
negative voltage comes to the current supervision line, and
therefore one supervision comperator does a wrong failure
reaction !

Workaround:

- step 1 -
Try to clean the space on the PCB around this supervison module.
(I soldered it out for cleaning, a resoldered it in)..

- step 2 -
This helps. But after weeks the problem returned again ....
I soldered in a resistor between the +Vaux (about 12..16V)
and this current measure line to compensate this negativ
voltage of the -12V line.
This is no relevant impact to the over-current protection,
as the resistor has a high value against the measurement
output.

This worked for me.
If you need help on this, please contact me ...

Christoph




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company:	christoph.plattner@alcatel.at

[parisc-linux] Re: Apollo 9000 power problem

[John David Anglin]

Christoph,

I saw your recent note on power supply problems.  It looks like
my 735(730) has suffered a similar failure in the recent blackout.
The symptoms appear similar to what you described a a couple of
years ago.  On power up, leds flash for 100-200 ms and then all
go out.

Did you replace the failed capacitor?  Adding a resistor between
the +Vaux line and the current sense line to compensate for leakage
between the -12V line and the current sense line seems like a
bit of a hack.

Do you have docs for the supply?

Dave

Re: [parisc-linux] Re: Apollo 9000 power problem

[Christoph Plattner]

Hello,

of course it is a "hack", but it is a constructive one, not
a bad thing like disconnecting the suppervision or so ...

I have replaced some of the capacitors, but it was not so simple
to detect the one, which has lost a bit of it's fluid ...

The problem is relly the layer of this chemicals of the capacitor and
the dust mixture, which generates the lack current. (I really have
problems to explain this all in English here ....)

I was not my thing to take the power supply out and hold it under
the water to clean, so I tried it with clothes, etc, but - as I
mentioned already in the last mail - some weeks later the problem
occured again. New dust on this checimal stuff .... (or new chemical
stuff ??? ...)

This SIMM-like suppervison thing checks six itmes on the power
supply (the other 6 comperators are use to generate the RESET
signal in case of "power good").

One measures the current. If the input of the comperator increases
2.35V (comming from meassure transformer meassuring the current
of some secondary linesm e.g. 5V, 12V...), then the protection
stops the power supply (the stop is done per thyristor, so one
short "stop" signal hold the power supply down until POFF/PON,
then the cycle starts again).

In idle operation (my test setup was a 10 Ohm + LED to see,
if the power is stable while repairing it), the voltage of
the current transformers is near 0V. All current transformers
have an own diode to one line. So if the output voltage of
the current transformes is lower the e.g. 0.6V (voltage of
the diode), behind the diodes the line has high impedance.
So the very low lack current of the near -12V line can drop
this line easy. If the voltage drops below 0V, the comperator
does not work correctly and asserts the "stop" (although
e.g. -0.5V is below 2.35, which should be OK !).

If there is an over current, there is a voltage on the output
side of the current transformer, and a representative voltage
is on the other side of the diode. This will pull up the the
line up to some voltage (higher than 2.35 leads to the stop ..).

So the 220KOhm resisitor only pulls the high impedance sense
line up against the "dust" resistor. But both "resistors" have
a high value against the output of the over current transformers,
if a big current is comming up.

So this "hack" is acceptable for me.
It was not acceptable for me, to  short-cut or isolate the
over-current protection (I did this for one day for tests, but
I could not live with this feeling, not having this important
protection.

And see the alternative. A new powersupply of this type costs
about 1000 EURO, an "fresh repaied" about 300EURO, an old one
- perhaps having the same problem soon - costs about 150EURO ...

So I am happy to have a correct working power supply with a
full functioning protection and a "well defined" hack !

Ok, I cannot take any warranty for others ..., but I thought,
I know what I am doing.

Further questions are welcome.

Christoph P.





John David Anglin wrote:
> Christoph,
> 
> I saw your recent note on power supply problems.  It looks like
> my 735(730) has suffered a similar failure in the recent blackout.
> The symptoms appear similar to what you described a a couple of
> years ago.  On power up, leds flash for 100-200 ms and then all
> go out.
> 
> Did you replace the failed capacitor?  Adding a resistor between
> the +Vaux line and the current sense line to compensate for leakage
> between the -12V line and the current sense line seems like a
> bit of a hack.
> 
> Do you have docs for the supply?
> 
> Dave
> _______________________________________________
> parisc-linux mailing list
> parisc-linux@lists.parisc-linux.org
> http://lists.parisc-linux.org/mailman/listinfo/parisc-linux
> 
> 



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-------------------------------------------------------
private:	christoph.plattner@gmx.at
company:	christoph.plattner@alcatel.at

[parisc-linux] Re: Apollo 9000 power problem

[Alexander Gabert]

hi,

On Fri, Aug 01, 2003 at 12:04:12PM +0200, E. Pavletic wrote:
> Hi Alex,

nice to meet you :-)

> 
> I've got an apollo 9000 series 735/90 and now I'm experiencing a problem
> like yours: when I try to switch the power on, the leds flash up for a
> part of a second and then it's dead again.
> I have no idea what's the matter.

when it starts blinking for less than a second, try pushing the button
again and again and keeping it in the middle of being pushed.
this way you shortcircuit the logic but do not turn it off again!
> 
> I've looked on the Internet, but there I've found discordant opinions:
> someone says that the problem is in the power supply, others (like you)
> that it is in the power switch instead.

the power switch was not the problem.
the power suply has gone bad.
a new costs around 150 euro :-(


> 
> Would you be so kind as to tell me how you resolved the problem and
> what's the real reason of this failure, if you know it?

as said, the power supply has gone bad and i did not find a way other
than replacing it...
www.gall.de

> 
> Thanks
> enzo

HTH,

Alex
> 
> 
> # From: Alexander Gabert <pappy@nikita.ath.cx>
> # Date: Fri, 10 May 2002 22:37:45 +0200
> 
> > hi fellows,
> >
> > tonight i ran into a major problem: one of my two hp workstations is
> > having problems with the power on switch:
> 
> > the button must be pushed and tricked more than 5 times to turn the
> > machine on (led's blink only for a second when you push the button
> > once).  i did not mind and just did not turn the machine off :-)
> >
> > but now, i have the problem that the machine runs for 5-6 minutes and
> > then suddenly powers off itself.
> >
> > i really suppose it to be a problem with the A1094-66541 PCBA Switch
> > that is the little power switch assembly behind the drive cage that is
> > connected to the leds with the small ribbon cable and connected to the
> > chassis backplane with a long cable.
> >
> > does someone of you (preferably in germany, or the best would be
> > munich) know somebody, who i may ask to get me such a part?
> >
> >
> > i am quite sure, that this PCB is generating the problems with
> > powering
> > on the machine and recently that it powers itself off.
> > some months ago i took the power switch PCB from my second machine and
> > put it into this one and the PCB worked, but i need it for the other
> > machine of course, which happens to be the web/mail server from which
> > i am currently writing and receiving my mails.
> >
> > thank you in advance for any help to get this machine up and running
> > again...
> >
> > alex
> 

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