Some old equipment restoration/repair/safety checks before real use - Page 1
Forum section: electronics / repair

author: reef.pi
author_rank: Contributor
timestamp: September 30, 2024, 04:57:53 pm
content: Hello,Over the years, in an attempt to one day spend time working on hobby projects, I have purchased a number of bench equipment. I have got power supplies, signal generators, multimeters and so on. They are quite old, I will try to get an aprox date of manufacturing once I start taking them one by one and properly check, but certainly they are at least 6-7 years old.I'd like to start using them, I read it is quite mandatory to replace old electrolytic capacitors if the device is more than 8 years old, even if they may look fine from the outside, is that correct?Another thing, I have read some stories and admittedly I am a little terrified, about IEC mains input filters, which are found in some, if not all of them. For some reason, occasionally, the capacitors inside of them tend to short causing a lot of smoke if not worst? Since they are positioned before apparatus power on/off switch, a safe alternative would be to use an extension socket with switch? Or just ditch them altogether?Anything else to check, replace?Thanks.Cornel

author: agent_power
author_rank: Regular Contributor
timestamp: September 30, 2024, 08:46:04 pm
content: 6-7 years isn't much.Tube based equipment from 50s, 60s and earlier will have electrically leaky wax / paper capacitors and needs to be checkedEquipment past 70s can have RIFAs / WIMAs which tend to crack and unleash the smoke, those are sometimes hidden inside the IEC inlet in a canEquipment past late 80s until early 2000s will have physically leaking electrolytics and/or RIFAsIf it's 2010 and later you can just plug it in

author: inse
author_rank: Super Contributor
timestamp: October 01, 2024, 12:14:31 am
content: Golden rule: If it ain’t broken, don’t fix it.If there were Rifa‘s in kit, they still have plenty of years of run-time before them.

author: reef.pi
author_rank: Contributor
timestamp: October 01, 2024, 10:24:53 am
content: The idea with caps replacement comes from xdevs, he was saying it is mandatory replacing caps on Keithley 2001 if the unit is 7 years older

author: coromonadalix
author_rank: Super Contributor
timestamp: October 01, 2024, 10:44:06 am
content: same hereaint broke dont fix it, but you can check for the famous Rifa's ... and old Shaffner iec line filters / ac socket ...do an internal visual checks for sure, bulged caps, leaked caps etc ... crust / dustlube pots or slide switches with good products, not cheap stuffcheck where you have big parts who can heat for solders quality, mostly psu's / big physical partsseeing people always changing caps without REAL problems .... and create REAL problems ...

author: lowimpedance
author_rank: Super Contributor
timestamp: October 01, 2024, 11:17:54 am
content: Quote from: reef.pi on October 01, 2024, 10:24:53 amThe Keithley 2000, 2001, 2002 are special cases for the mandatory electrolytic cap replacement as they do leak with dire consequences for the instrument if not discovered in time.Otherwise best is to check them, particularly if subjected to heat, high ripple currents etc, and only replace if found to be suspect.Just give your gear a good inspection if they are in good condition to give yourself confidence. If they have had a hard life before you acquired them then spend more time on it, cleaning and checking for issues before power up.

author: reef.pi
author_rank: Contributor
timestamp: October 01, 2024, 11:49:06 am
content: I got it now, thanks everyone for their comments.I have thought all equipment should gone thru the same process of caps replacement, not ideal, I have accumulated quite a number of various equipment over the years, it will take me quite some time to do it. But then, I don't want to risk them neither, if it has to be done, then I shall do it.Starting with bench multimeters, I got two Keithley 2001, one Keithley 2700 with some expansion boards, one HP 3478A and a Fluke 8842A; all of these should undergo caps replacement? The only quite new bench multimeter I have is a TTi 1908, that was bought new, but again, maybe 7 years older now, also caps replacement? This one still has the original foil protection over its display.Would a visual inspection and cleaning be actually good enough for some of them?

author: squadchannel
author_rank: Frequent Contributor
timestamp: October 01, 2024, 12:00:52 pm
content: It is too much of a waste to throw away a test equipment.7 years is still safe and sound.In my case, I disassemble it, including replacing the capacitors, if they are 20-25 years old after manufacture.Inspection items include,-Clean dust from the inside of the capacitor.-Check for damage to the internal circuit board and capacitors.-If there is a fan, disassemble it, clean and grease the bearings.-Check for the use of RIFA.-Check the date of manufacture of AC input filters.If the test equipment contains a HDD, remove the HDD and backup.This is very important. If it gets damaged, there is no way to recover it.Some older test equipment, such as the 3478A, may use RAM with hanged battery to store calibration data.Batteries, of course, wear out. If they wear out, the calibration data will be lost.They should be replaced.Also, for us hobbyists, I think most of the expensive test equipment such as Tek, hp, Agilent, etc. are used.All my test equipment are used. 20 years has definitely passed.Well, I am a germaphobe, so when I get a used test equipment, I basically disassemble it to the point where I can disassemble it, one screw at a time, and clean it.I also do the aforementioned inspection items and make sure they are in good working order.Capacitors are replaced at that time.RIFA is a time bomb that can explode at any time. Immediately replace the capacitors with TDK capacitors.I get attached to it, so well, it's nice for me.It is not surprising that terminals and other parts are rusted. Especially hp, the BNC is often rusted.In my case, polish those with minor damage, but in the case of severe damage, look for compatible items to replace them.The question is how much money can I put into that test equipment.I'm only 20 years old and I don't know how much better this maintenance will be, but it will work until I pass it on to my grandchildren.PS.It is NOT allowed to use capacitors made in China. No, I am not hating on you because I am Japanese.I just think nichicon or chemi-con is the best for durability.

author: tggzzz
author_rank: Super Contributor
timestamp: October 01, 2024, 01:20:37 pm
content: Quote from: reef.pi on October 01, 2024, 11:49:06 amAny operation involves a risk-reward tradeoff.Replace RIFAs on sight with appropriately rated X/Y capacitors before they self-immolate. Benefit: self-immolation means you can sometimes pick up good equipment very cheaply, e.g.https://www.ebay.co.uk/itm/146048945605No, I didn't bidOther equipment capactors depends on the specific equipment and capacitor type. (There are some milspec tants that cost £70 each, and probably don't need replacing) If you can't find specific information, close visual inspection and measuring ripple voltage is often indicative.The other major point is battery-backed calibration constants. Tek 24*5A/24x5B (not 24x5), have them. HP3468 has them and I expect the 3478 does too.With the latter there are ways to replace the battery without losing the calibration, and ways you caneasilylose the calibration. Procedures are well documented on the web.Replacement electrolytics: make sure the ripple current and frequency is appropriate. Higher temperature spec tends to mean longer lifetime. Panasonic, Nichicon, Rubycon, Wima, Nippon Chemicon are all decent.

author: lowimpedance
author_rank: Super Contributor
timestamp: October 02, 2024, 01:55:52 am
content: Quote from: reef.pi on October 01, 2024, 11:49:06 amLots of good advice aboveI would definitely replace the electro's in the 2001 and check carefully the 2700, (not sure if that model is affected the same... but still!).For the other two just check them first.The 3478a has a CAL battery backup as well as the infamous RIFA mains suppression caps that should be replaced. Search the forum for the proceduresAs for the 8842a, check the mains transformer PCB joints for cracked/dry joints etc. Most likely the Vacuum Fluorescent Display is worn and the brightness has dropped right off which is common on these meters. So depending on your tolerance for reading the display you could leave it or there is a LED replacement which may still be available, see here:https://www.ebay.com/itm/156079740588and,https://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/