Replacing HP oval style power connector - Page 1
Forum section: electronics / repair

author: GregDunn
author_rank: Frequent Contributor
timestamp: September 17, 2018, 02:37:10 am
content: I have an old HP331A with the oval power connector. Fortunately, I have the cable for it, but unfortunately it's starting to degrade with age and I'm not sure how much longer it will be safe to use. I know:1) the connector can be replaced with an IEC standard socket.2) there are two types of "oval" power cables with hot and neutral wired oppositely. Fortunately, I know the polarity of this one.Part of me wants to keep the instrument original, and part of me says "update it and prevent future mishaps". Updating to a new IEC standard socket is something I can do easily with a nibbling tool, but I'm just curious if anyone has done this and has anything to offer that I might not be considering.There's also the possibility that I may acquire old HP gear in the future which doesn't have the cord; and I know the HP-compatible cords are getting harder and harder to find.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 17, 2018, 04:16:29 am
content: Sure you can replace the old connector with a new IEC C-14 panel connector.If you have enough space, the ability to do clean surgery, and the willingness to destroy the original vintage.OTOH, cables still appear to be available. I would just buy several to stock up before the prices inflate even more.

author: GregDunn
author_rank: Frequent Contributor
timestamp: September 17, 2018, 05:19:36 am
content: Do you mind sharing examples of where the power cables can be readily found? I did a search and after numerous hits of "out of stock" and ridiculous prices I finally gave up on them. But then I only tried the ones which came up high on a Google search, as well as the usual suspects of Amazon and the Bay. I'm not really interested in getting into a bidding war on what should be a $5 cable.Original vintage is only worth so much to me; by the time I've spent more than an IEC socket + a good cable costs, it doesn't really bother me.

author: Smith
author_rank: Frequent Contributor
timestamp: September 17, 2018, 06:00:51 am
content: I replaced the connector in my 332a, because someone glued the original. Had to file off a few mm, but it was quite easy. I used an old connector to make it look somewhat original. I was quite pleased with the result.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 17, 2018, 08:58:59 am
content: Quote from: GregDunn on September 17, 2018, 05:19:36 amDunno how you define "readily" or "ridiculous price"? They are a disappearing commodity, so finding them for $5 seems unreasonable. Depends on how important "original" is to you. Are you just wanting something workable, or are you trying to preserve a museum piece? Dunno what your priority is?https://www.ebay.com/itm/Old-Style-HP-Tektronix-IBM-AC-Power-Cord-for-Vintage-Test-Equipment-8FT-3-prong/252979611909https://www.ebay.com/itm/Vintage-Oval-AC-Power-Cord-3-Prong-7-5-Ft-NEW-OLD-stock/253835317251https://www.ebay.com/itm/Belden-800-5121-Vintage-Oval-AC-Power-Cord-3-Prong-7-5-Ft-NEW/332283807942Many other examples around $30. I agree that is frightful compared to the original price. But that was 50 years ago.

author: GregDunn
author_rank: Frequent Contributor
timestamp: September 17, 2018, 03:01:48 pm
content: I appreciate the sanity check on prices; I had another look last night and got much the same answers.I've already replaced the dodgy caps in the unit as well as substituted for a missing unobtainium pot, so it's no longer "vintage" in any way. In my view, spending nearly as much for a cord as I have invested in the unit is crossing the line and at that point I think upgrading the socket is the right way to go. It'll be safer in the long run as well, I believe.I like Smith's approach, though I'm sure the metal socket is elusive as well. I'm going to a couple of hamfests over the next few weeks, and if I can't find a cord in a "make offer" bin I think I'll just go with the updated IEC connection. Thanks to all for the input.

author: N2IXK
author_rank: Frequent Contributor
timestamp: September 17, 2018, 03:22:35 pm
content: One note of caution on those old HP style oval power cords. There are 2 standards for how they are wired, which swap the hot and neutral conductors. HP test gear used one standard, but the desktop calculator/adding machine market (the other major user of these cords) tended to use the other standard. Just something to look out for when working with this gear.I generally prefer to swap over to a modern IEC type connector whenever there is room available to do so.

author: GregDunn
author_rank: Frequent Contributor
timestamp: September 17, 2018, 04:23:42 pm
content: Yes, I was aware of that. And it means that even if I find a cable, there's still a chance it will be wired incorrectly for my equipment. Altogether a better choice to replace the socket, I think.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 17, 2018, 05:00:28 pm
content: Quote from: N2IXK on September 17, 2018, 03:22:35 pmI rather like the EU convention of just assuming that BOTH of the conductors are "hot". With proper commercial/laboratory gear, it shouldn't be difficult to wire it so that it doesn't matter which side is "hot".QuoteYes, that is my practice also. I have a big bag (lifetime supply) of IEC panel connectors which I got in the Tektronix surplus storeThey may have tossed them because while the contacts/pins are nice and bright, they aren't very solderable.I have to use extra flux to get them to solder properly before the plastic shell melts.Or perhaps they gave up on the solder-lug variety in favor of push-on tab termination?

author: Smith
author_rank: Frequent Contributor
timestamp: September 17, 2018, 09:04:10 pm
content: Quote from: GregDunn on September 17, 2018, 03:01:48 pmIf I remember correctly my IEC inlet came from an old Delta Electronika power supply, some older E015-2 or equivalent. I had one lying around with a shot transformer. Reasonably expensive for the outlet alone. Havent seen many devices with these types of inlets, even in older (>30yo) devices.

author: factory
author_rank: Super Contributor
timestamp: September 21, 2018, 09:34:48 pm
content: Quote from: GregDunn on September 17, 2018, 03:01:48 pmThe metal socket is easy to find & cheaper than the power cords, search ebay for PH163 and you should find some sockets.Yes the cords for 1960's HP equipment have reversed polarity as has already been mentioned, new replacement ones should be labelled to indicate this (see attached Volex 17952 PDF from 2007), Volex discontinued them a few years ago, but there seems to be no shortage of new or NOS cords on ebay under various names including Belden, Volex, Alpha, etc.Sphere have some new Alpha 543 ones here (scroll to the bottom of the page);http://www.sphere.bc.ca/test/wallwarts.htmlI bought a couple from them a few years ago, they always seem to have the comment about them being hard to find or last ones on their listing, but always seem to find more.Also note that IEC sockets can also fail after many years, I've changed a few with bad earth/ground connections due to the crap riveted type construction of the pins. And I expect after 40+ years the pins on IEC connectors will probably get tarnished too, especially if the equipment is stored badly in damp sheds/garages or attics/lofts like a lot of vintage stuff seems to be, not that that can't be easily dealt with a bit of cleaning.By the way if you end up buying more old HP equipment you will probably end up with plenty of the old cords, just like I have.David

author: bitseeker
author_rank: Super Contributor
timestamp: September 22, 2018, 02:48:18 am
content: You can get the cords on eBay for around $15. They don't stick around long (maybe people snatch them up and resell them?), but it's not impossible. A couple of them sold this week, and several sold last last month, in that price range. I paid $16 each for mine a year or so ago.

author: Krischu
author_rank: Newbie
timestamp: October 15, 2022, 07:58:23 am
content: Quote from: Smith on September 17, 2018, 06:00:51 amHi, do you happen to know a source for the left one of the depicted plugs?