-----Oorspronkelijk bericht----- Van: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org] Namens Tony Duell Verzonden: zaterdag 15 januari 2011 18:20 Aan: cctalk at classiccmp.org Onderwerp: Re: HP 8018A heath sink getting hot equipment. That does sound rather hot. Personally, if I can't keep my hand on a heatsink, then I want to investigte (DO NOT try this with SMPSUs where the heatsinks are often live!) Ifr you don't already have it, you can get the operating/service manual from http://www.agilent.com/ . Once you've found the 'manuals page, you enter the model number (8018) and it'll give you a link to download the pdf manual. Said manual looks to contain full schematics, etc. Anyway, I've not really looked at it, but I did notice that the PSU is entirley linear, and that there's a -5.2V rail, presumably for ECL. To me that suiggests it might run hot, but how hot I don't lnow. -tony I've the manual and did some measurements, there are 3 current sense resistors one for each supply voltage. The 25V and -5.2V current are within spec. the 5V current is a little high but in spec when I remove the HP-IB option card. ESR of the psu elco's < 0,03 Ohm and tantalium cap's <1 Ohm on the board are good . Measuring the heath sing temperature gives 68-70 degrees Celsius, but the instrument keeps running stable. So I think it's 'designed' to get hot... -Rik

I really cn't beliueve it's that short. 2000 hours is less than 100 days. Which, given a reaosnable usage period of the equipment (say 8 hours a dayu on average) would suggest that on average an electrolytic capacitor would need replacing after 1 year. And that is not what I am seeing. Of course I've replaced electrolytics in classic computgers. But I've certainly not replaced all of them. Many of muy machines are over 30 years old, they have been used, and have had no capacitors fail at all. -tony