From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from viefep12-int.chello.at (viefep12-int.chello.at [213.46.255.25]) by dsl2.external.hp.com (Postfix) with ESMTP id E04454843 for ; Thu, 21 Aug 2003 15:32:56 -0600 (MDT) Message-ID: <3F453A84.5040305@gmx.at> Date: Thu, 21 Aug 2003 23:32:52 +0200 From: Christoph Plattner MIME-Version: 1.0 To: John David Anglin Cc: parisc-linux@lists.parisc-linux.org Subject: Re: [parisc-linux] Re: Apollo 9000 power problem References: <200308182034.QAA13970@hiauly3.hia.nrc.ca> Content-Type: text/plain; charset=us-ascii; format=flowed Sender: parisc-linux-admin@lists.parisc-linux.org Errors-To: parisc-linux-admin@lists.parisc-linux.org List-Help: List-Post: List-Subscribe: , List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: 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 > > -- ------------------------------------------------------- private: christoph.plattner@gmx.at company: christoph.plattner@alcatel.at