Cleaning up old equipment - Page 1
Forum section: electronics / general

author: Entropia
author_rank: Regular Contributor
timestamp: August 15, 2012, 05:56:24 pm
content: I bought this lovely old HP/Agilent 6632B DC Power Supply. Cosmetically it's seen better days (but calibrated just two days ago to within spec!). There are old sticker leftovers (both paper and plastic stickers) as well as regular dirt. What chemicals should I use to avoid damaging the plastics? I think the first step is to try mild soap water but that's probably not gonna make it all go away... Any ideas?Also, if you have any before/after shots of your cleaned up equipment, please do share!Here's the 6632B in its current condition:http://entropia.1g.fi/kuvat/Projektit/HP+6632B/IMG_6786.JPG/_big.jpg

author: Astroplio
author_rank: Regular Contributor
timestamp: August 15, 2012, 06:44:57 pm
content: I like to remove plastic parts and dirty metal brackets and give them a good bath in hot soapy water, then wipe them and let aside to dry, or use hot air gun (low-medium heat) if I am in a hurry.I use isopropyl alcohol with cotton swabs for places I can't remove and are hard to reach inside the equipment. Care must be taken though because sometimes cotton fibers are left behind.George

author: JuiceKing
author_rank: Regular Contributor
timestamp: August 15, 2012, 06:48:37 pm
content: I've had good luck with Windex (active ingredient is ammonia) for getting grime off of plastic, and Goo-Gone for removing sticker residue. Both are pretty mild and haven't damaged any HP equipment from 1963-1992 or so. (I've had Windex remove the "V" from the INVERT button on a late 70s Tek scope--the paint is not robust, so you must use special care. But with HP that's never happened.)I've used an Xacto knife to get under and remove a thick plastic sticker from a metal (aluminum) front plate. It was very hard to get it all off, but with much effort and only slight scratches to the finish of the instrument face, I managed to clean it up. Since then, I've left those thick plastic stickers alone. Paper stickers are usually no problem if you use Goo-Gone to dissolve the gum.I'm very cautious on any clear plastic (meters, displays, etc.) because it's all too easy to scratch or cloud them, but I've found that clearcoat car polish can help remove light scuffs.

author: LaurenceW
author_rank: Frequent Contributor
timestamp: August 15, 2012, 06:53:54 pm
content: I'd agree it is worthwhile doing some minor dismantling of the outer case, front panel, knobs and buttons. Try washing them first in warm, soapy water. You might also be able to buy mild cleaning liquids which will dissolve and remove sticky label glue. Do not apply too much pressure, though! it is easy to rub off some types of silk screen print, if you apply too much "elbow grease" (pressure)

author: Entropia
author_rank: Regular Contributor
timestamp: August 15, 2012, 07:39:15 pm
content: Thanks for the tips so far. The instrument is already half-way dismantled on my desk, I'll try the warm soapy water first. I'm gonna install banana plugs to the front panel in the same go. I'll let you guys know how it goes.

author: robrenz
author_rank: Super Contributor
timestamp: August 15, 2012, 11:38:08 pm
content: The melamine sponges "magic erasers in the US" do an amazing job with whatever solvent/cleaner you are using.I use IPA with one on most all plastics and it gets stuff off that does not come off with just a cloth. A must have for cleaning old equipment.

author: slateraptor
author_rank: Frequent Contributor
timestamp: August 16, 2012, 12:43:22 am
content: You'd be surprised what a toothbrush, mild soap, and hot water can wash away.Before and after pics of my HP 3468A, which was in comparable cosmetic condition when acquired from a university surplus auction.P.S. I removed the enclosure prior to cleaning, so not sure how that will work out with your cal sticker and all...that is, if you care.

author: Entropia
author_rank: Regular Contributor
timestamp: August 16, 2012, 05:18:12 am
content: robrenz: I remember seeing a product called "magic sponge" in some stores that claim to clean up any stains... Better give that a try too!slateraptor: Nice transformation! The meter looks like new after your treatment. :-)

author: G7PSK
author_rank: Super Contributor
timestamp: August 16, 2012, 05:26:35 pm
content: Remove old glue from stickers with alcohol and then buff the plastic up with T cut this will bring the plastic and paint work up like new.

author: dcel
author_rank: Regular Contributor
timestamp: August 16, 2012, 06:07:23 pm
content: I have been cleaning computers and equipment cases with 'Formula409' cleaner for years. It wont harm plastics and will usually not harm paint, dilute 50/50 with water to test. I disassemble my meters occasionally and use the 409 to clean up the cases from all the shop grime. To protect the stuff I have cleaned, I use Lemon Pledge liquid in the trigger spray, wipe on, buff off.Chris

author: slateraptor
author_rank: Frequent Contributor
timestamp: August 16, 2012, 11:43:54 pm
content: Quote from: Entropia on August 16, 2012, 05:18:12 amBelieve me when I say it looks even better in person; that pic doesn't do it any justice.

author: metalphreak
author_rank: Frequent Contributor
timestamp: August 17, 2012, 08:43:08 am
content: There's a product called "Goof Off" that's sold in Australia. Works pretty well at dissolving adhesives. They have a few different versions, some of which are safer on a wider variety of surfaces (mostly plastics).Available from Bunnings for any Aussies who need it

author: JuiceKing
author_rank: Regular Contributor
timestamp: August 17, 2012, 11:06:19 am
content: Quote from: metalphreak on August 17, 2012, 08:43:08 amWe have Goof Off here in the U.S., too. It's used to remove latex paint splashes and is considerably more aggressive than Goo-Gone. (Obviously, the two are easily confused. I mixed them up myself and made a mess of things once!) I wasn't aware that Goof Off comes in different versions. You really need to be careful with this stuff.

author: metalphreak
author_rank: Frequent Contributor
timestamp: August 17, 2012, 02:53:41 pm
content: The stuff I have is labelled Goof Off 2, comes in an orange spray bottle, and is safe for all plastics (glycol ethylene and n-propanol based). The other one I had was just "Goof Off", came in a small metal tin can (like zippo lighter fluid) and is NOT safe on all plastics (it's xylene based, so anything that says xylene, test it on a spot first before going nuts).

author: AndyC_772
author_rank: Super Contributor
timestamp: August 18, 2012, 11:59:57 am
content: Quote from: Entropia on August 15, 2012, 07:39:15 pmI wonder whether we bought the same PSU from Ebay? There's a guy in Finland who was selling off a whole pile of these at a remarkable price; I bought two for myself, and a couple of my customers bought them too on my recommendation. It's a shame I don't think he has any more.Fortunately mine didn't need quite so much cleaning up - just a wipe over the case with a damp sponge and a quick scrub with PCB cleaner to get off a bit of label residue.I thought about installing banana terminals on the front panel but decided against opening up a working, calibrated unit just to risk making a mess of it. So, instead I attached a small plastic box with the banana terminals to one of the rack mounting brackets, and ran wires from there to the screw terminals on the back of the unit.I fitted 5 terminals so I can retain the use of remote sensing, and have optional earthing too if required. Inside the box I fitted 10 Ohm resistors between the main output jacks and the sense terminals, so I still get the correct voltage at the terminals even when the remote sense jacks aren't used.Incidentally, the manual is wrong about the screw size for the terminals at the rear of the unit - mine were M3.5 x 6, not the 6-32 x 3/8in that the manual states. Maybe they were changed at some point during the model run, but I have both an earlier HP branded 6632B and a later Agilent one, and both are identical.Here's the end result. I can't pretend it's especially pretty, but it's certainly functional and that's what matters (to me!):

author: T4P
author_rank: Super Contributor
timestamp: August 18, 2012, 12:14:57 pm
content: Locally there's 5 6632A going for 100 bucks each, i assume that's decent?Well at the same time there's a 6632B Agilent labelled that has it's cal sticker missing and something else ... if i recall not quite detrimental to the functionality of the PSU

author: Entropia
author_rank: Regular Contributor
timestamp: August 19, 2012, 05:08:32 pm
content: Quote from: AndyC_772 on August 18, 2012, 11:59:57 amProbably the same guy sold me the unit. Somehow I got the feeling he bought them from a bankrupt company's equipment liquidation or something like that, but I don't know for sure. I didn't buy mine via eBay but I paid silly money so it's still probably the same guy. :-)Here's mine after some TLC and banana plug installation:

author: dcel
author_rank: Regular Contributor
timestamp: August 19, 2012, 09:34:18 pm
content: Quote from: Entropia on August 19, 2012, 05:08:32 pmNice job! Trashed to treasure! Damn those things are big. Is there a lot of empty space inside them? Nice mod with the banana jacks.Chris

author: Fluxed Matter
author_rank: Regular Contributor
timestamp: August 20, 2012, 01:07:18 am
content: I would like to share my latest acquisition. It is an HP 6205C that I got off fleabay real cheap. I was listed as "for parts only" but after checking it over I found that it is working. The reading on the meters are off but I think I can fix that. I have to start searching for the service manual and see if I can find it so I can clean it up and check the calibration. Here are some pictures that I took earlier. Enjoy

author: Entropia
author_rank: Regular Contributor
timestamp: August 21, 2012, 06:40:20 am
content: Quote from: dcel on August 19, 2012, 09:34:18 pmThanks! There is certainly free space inside, but not as much as you'd think. There's three PCBs, one for DSP stuff, one for power stuff and the front panel PCB. The power PCB takes up half of the bottom area and the other half is taken by the enormous transformer and the DSP board.Quote from: Fluxed Matter on August 20, 2012, 01:07:18 amNice find. A bit of elbow grease and it's as good as new. :-)