HP Forum Archive 19

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What type of caps are used in Classic power supply? Message #1 Posted by Dan W on 19 Sept 2009, 1:37 p.m. Hi all, In the Classic series what type of capacitors are used in the power generating circuits on the main boards? These are the silver radial lead caps, 2.2 uF to 60 uF. They appear to be non-polarized, but I think they might be non-polar electrolytics. On the HP-67 they switched to Tantalums throughout. TIA

Re: What type of caps are used in Classic power supply? Message #2 Posted by Walter B on 19 Sept 2009, 1:49 p.m., in response to message #1 by Dan W Assume baseball ... (sorry, couldn't resist ;)

Re: What type of caps are used in Classic power supply? Message #3 Posted by Karl Schneider on 21 Sept 2009, 1:24 a.m., in response to message #2 by Walter B Quote: Assume baseball ... (sorry, couldn't resist ;) I, too, find it annoying when a capacitor is termed a "cap"...

Re: What type of caps are used in Classic power supply? Message #4 Posted by Garth Wilson on 21 Sept 2009, 4:08 a.m., in response to message #3 by Karl Schneider Quote: I, too, find it annoying when a capacitor is termed a "cap"... To make it worse, the small values that are specified in pF (picofarad) are often referred to as so many "puff." This bugged me just a tad when I worked in applications engineering at a company that made VHF and UHF power transistors.

Re: What type of caps are used in Classic power supply? Message #5 Posted by DaveJ on 21 Sept 2009, 6:49 a.m., in response to message #4 by Garth Wilson Quote: To make it worse, the small values that are specified in pF (picofarad) are often referred to as so many "puff." This bugged me just a tad when I worked in applications engineering at a company that made VHF and UHF power transistors. That's how real electronics guys talk! And 10uF is "10 mike" Then of course you have the old timers who refuse to use nanofarads, it's "100,000 puff" son! Dave.

Re: What type of caps are used in Classic power supply? Message #6 Posted by Dave Shaffer (Arizona) on 21 Sept 2009, 7:56 p.m., in response to message #3 by Karl Schneider Quote: I, too, find it annoying when a capacitor is termed a "cap"... Can I call it a "condensor" instead?! That really dates me.

Re: What type of caps are used in Classic power supply? Message #7 Posted by Bart (UK) on 19 Sept 2009, 6:25 p.m., in response to message #1 by Dan W Looking at an explanation of the 35 & 45 PSU here, one can see from the photograph of the 45 that they seem to be polarised axial capacitors, with the lead starting with a thicker bit being +ve.

Re: What type of caps are used in Classic power supply? Message #8 Posted by Randy on 19 Sept 2009, 9:10 p.m., in response to message #1 by Dan W Quote: They appear to be non-polarized, but I think they might be non-polar electrolytics No, polarized for sure as they're Kemet hermetically sealed tantalums... which is why they still work after all these years. FWIW, HP always noted the + terminals or pin 1 with a square pad on the their pc traces.

Re: What type of caps are used in Classic power supply? Message #9 Posted by Dan W on 20 Sept 2009, 12:06 a.m., in response to message #8 by Randy Quote: No, polarized for sure as they're Kemet hermetically sealed tantalums... which is why they still work after all these years. FWIW, HP always noted the + terminals or pin 1 with a square pad on the their pc traces. Yep, you're right, I see Kemet written on one of them. That's the info I was looking for. thanks. I have 2 cases where I see a problem with a cap but you're right, these caps are rarely the problem. Funny thing, I went to Digikey today and ordered a set of replacement caps - before I read this, and ended up ordering Kemet axial Tantalums. On the pads, the square pad for positive is true for the 65 and 67, but not for the 35, 45 or 55. These have a small triangle next to the positive pad.

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