Replacing old capacitors with modern ones - Page 1
Forum section: electronics / beginners

author: mehoff
author_rank: Newbie
timestamp: May 12, 2025, 09:08:14 pm
content: Hi, I'm not really a hobbyist, just someone who's trying to get something to work. I have an old ultrasonic cleaner from 1980 that has old-style canister capacitors in it. They have specs that are very hard to find. I have spent a lot of time looking online, but I feel like I'm looking for something that doesn't exist. One capacitor is marked .002 mfd 3.5 kVAC and the other is .022 mfd 3700 VAC. I would ideally like to find modern replacements. I've attached a picture of the two units. I have contacted the manufacturer and they don't have anyone working there who knows anything about this model, or they're not talking. Thanks for any help you can offer.EDIT: I have disposed of the ultrasonic cleaner. Thank you all for your input.

author: jwet
author_rank: Frequent Contributor
timestamp: May 13, 2025, 06:00:10 am
content: These are oil filled capacitors that just aren't very common anymore. They were used in old RF Transmitter equipment. The good news is that made trillions for military equipment a long way back. The best source would be Surplus Sales of Nebraska. You can likely find the values but you might have to do a little mounting work.Here's a link-https://www.surplussales.com/categories/2651-oil-capacitors-0-to-099-microf/

author: calzap
author_rank: Frequent Contributor
timestamp: May 13, 2025, 06:55:12 am
content: You say you're not a hobbyist, and presumably not an electronics engineer or technician. I'm concerned that you are working with equipment that has lethal voltages. Recommend you get some knowledgeable, live help with the project. Mike

author: RoGeorge
author_rank: Super Contributor
timestamp: May 13, 2025, 07:39:22 am
content: Those are high voltage capacitors, and they will probably outlast everybody alive today. Sure, any component can become defective at some point, but those are not the typical low ESR electrolytic capacitors that "must be all replace after a couple of years".Why do you want to replace them?Have you measured the capacitors?

author: Whales
author_rank: Super Contributor
timestamp: May 13, 2025, 10:38:14 am
content: Oil filled capacitors explode when they fail (it's fun trust me). The oil does not last forever, it degrades over decades.The oil in these is likely toxic, wear gloves if you spot any leaks.What's wrong with the ultrasonic cleaner?

author: mehoff
author_rank: Newbie
timestamp: May 13, 2025, 01:03:09 pm
content: I'm aware of the dangers surrounding capacitors. After testing the machine, I touched multimeter probes to the capacitors and watched the (low) voltage drain to zero within seconds. My hope is that I can find new capacitors, install them, and have a working machine, and never have to deal with charged caps again.

author: mehoff
author_rank: Newbie
timestamp: May 13, 2025, 01:13:38 pm
content: When I bought the ultrasonic cleaner as government surplus, I filled the tank with water, plugged it in, turned on the power, and flipped the switch for the generator. The tank hummed and the water rippled--for about a second. After a silent 15-20 seconds, it hummed and rippled again, then another 15-20 seconds of silence. It did that a few times, then I decided to shelve the project for a while.Recently, I brought it out again and this time I let it run for a while. The intervals gradually became shorter and shorter until the on and off periods were about the same ( one second on, one second off). I decided to switch off the generator but leave the power on overnight, and hopefully charge the capacitors. The next morning, the machine would do nothing--no on, just off.My multimeter's capacitance readings are suspect, as I tried testing capacitors that I knew were good but read bad, so I don't know the state of them. But at the end of the last round of testing, I tested for voltage after shutting down, and the readings dropped to zero within seconds.

author: mehoff
author_rank: Newbie
timestamp: May 13, 2025, 01:15:55 pm
content: Thank you for the link. I haven't had a chance to search, but it looks promising.

author: calzap
author_rank: Frequent Contributor
timestamp: May 13, 2025, 03:30:22 pm
content: I don’t know what voltage the ultrasonic cleaner has internally, but having caps rated at several thousand volts implies a high operating voltage. Most multimeters aren’t rated for this range. Mike

author: Uunoctium
author_rank: Frequent Contributor
timestamp: May 13, 2025, 04:12:14 pm
content: my humble suggestion is a replacement with MKV capacitors, wich are still in prodution. Very common brand were Siemens-MKV and after sale to EPCOS now under TDK brand.https://www.tdk-electronics.tdk.com/download/530830/782552aee3a6f87ddbd8108b964820fa/pdf-pqs-mkv-ruggedtypes.pdfIf you could find a similar model to yours, make sure they are marked "No PCB" or "Non PCB"!Bayer still has a very expensive legacy to settle from its acquisitions. One school alone, which had PCB capacitors in ceiling lights as part for reactive current compensation in the '70s, will have to pay Bayer billions in reparations.Long term uptake of slightest doses of PCB's are liver and nerve toxic .I bet, the one shown in picture on the left is filled with.

author: mehoff
author_rank: Newbie
timestamp: May 15, 2025, 06:26:03 pm
content: Thank you everyone for your kind input. I have decided to scrap the project. Even though it would be a nice setup if I could get it to work, it's too old and too much work to reach the finish line. Besides, I found two more oil-filled capacitors under the top panel, bringing the total number of unfindable parts to four. And who knows how long the vacuum tubes (!) would last before I'd have to replace them, too.

author: CaptDon
author_rank: Super Contributor
timestamp: May 15, 2025, 07:19:53 pm
content: Those oil filled caps are likely to be in 100% like new condition!! You don't test capacitors by how fast the voltage drops to zero!! Besides, their capacitance value is very small to begin with. Chances are better a resistor has gone way off value and gotten worse while you were testing the unit. How do you know the tubes have any life left in them? That may be why the unit failed in the first place. What are the tube numbers?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: May 15, 2025, 09:38:05 pm
content: As long as the oil does not leak from these caps, they really do not fail very often, If there is no bleeding resistor they can charge up by themselves from the environment and are stored with a wire short across the leads. There are probably high value bleeder resistors in the circuit.

author: Zero999
author_rank: Super Contributor
timestamp: May 16, 2025, 07:20:53 am
content: Quote from: mehoff on May 13, 2025, 01:03:09 pmWhy do you think the capacitors are bad? Refer to your other post:Quote from: mehoff on May 13, 2025, 01:03:09 pmThat implies the capacitors are good, because they held a charge. It's not conclusive, but it does point towards something else being the problem.

author: geggi1
author_rank: Frequent Contributor
timestamp: May 16, 2025, 08:16:59 am
content: These capacitors have low capacitance. You could get a bunch of 500v or 1000V capacitors and make a series parallel circuit of these to get the correct value. This is common on older tube based CB amplifiers.Dependent where the capacitors are placed in the circuit the capacitance might not be very critical.

author: Zero999
author_rank: Super Contributor
timestamp: May 16, 2025, 09:30:58 am
content: Quote from: geggi1 on May 16, 2025, 08:16:59 amBear in mind there are other things to take into account, other than voltage and capacitance. These capacitors will have a low ESR and low dielectric loss, making them suitable for high currents, at high frequencies. Smaller ceramic and film capacitors will burn if subject to the same conditions, even if they have sufficient voltage ratiing.

author: factory
author_rank: Super Contributor
timestamp: May 16, 2025, 01:07:02 pm
content: Is there some kind of timer function built into this cleaner? the description of it cycling on & off makes me think it could. And the on/off period becoming shorter also makes me think the fault is timer related, what else is in this machine that you didn't photo?What is the brand/maker that has no interest in their history, or are they just badge engineering someone else’s product and dumped all their archive?David

author: mehoff
author_rank: Newbie
timestamp: May 16, 2025, 06:12:51 pm
content: It's a reputable American brand that has been around for almost 100 years. My guess is that they moved on to solid state decades ago and decided to never look back. Besides, after 45 years, anybody who knew anything about the old technology has long since retired.It has a switch that can time the machine or, if turned the opposite way, allow it to run indefinitely. It's an electromechanical switch, like you have on your toaster oven. Pretty sure that's not the problem, but what do I know. Most of the suggestions I'm getting are going straight over my head.I bought this machine for short money and, when I found out it had problems, I hoped I could fix it with short money. The only option I can think of now is to spend a raft of money to ship this tank to an ultrasonic repair shop (they do exist), wait for an estimate that could break me, then spend another raft to have it shipped back to me. Nah.I’m going to scrap it.

author: radiolistener
author_rank: Super Contributor
timestamp: May 16, 2025, 06:26:10 pm
content: be careful, some of these old age oil-capacitors can contain extreme toxic substance inside.

author: BillyO
author_rank: Super Contributor
timestamp: May 16, 2025, 11:10:36 pm
content: Safely dispose of this at a hazardous waste depot, then go out and get yourself a nice cheap Chinese ultrasonic cleaner. They work well and keep working. I've had mine for 13 years and no problems. I see now 10 liter cleaners with temperature control and digital timers are going for about $100. Replacement capacitors could well cost more than that and may not even be the problem.

author: CaptDon
author_rank: Super Contributor
timestamp: May 17, 2025, 09:56:09 pm
content: Some oil filled capacitors can have various degrees of PCB content. PCB's are known to cause cancer, however, so does diesel fuel and almost any other petroleum distillate. Having handled a few slimy leaky capacitors has no real threat assuming you don't lick your fingers or the capacitors and wash your hands afterwards. You know how they destroy PCB contaminated oil.....In a typical gun style oil burner!!! That's right, they simply burn it. There must be tens of thousands of ham radio operators who obtained 'inerteen 50% PCB transformer oil' for their Heathkit Cantennas. Heathkit recommended contacting your local power company to obtain transformer oil and we are talking a time frame of mid 60's up until the end of production in the '80s or even 90's. No one wants cancer but I think the real hazard was blown way out of proportion!!! We had PCB contaminated capacitors at our commercial broadcast facilities and it was nearly moronic for all of the stickers we had to place on things including warnings on the doors to advise the fire departments that the building contained 'hazardous substances'.

author: mehoff
author_rank: Newbie
timestamp: May 18, 2025, 07:53:22 pm
content: That's true here as well. The state of California passed a law decades ago that requires any manufacturer in the state to put a label on their product if it contains a known carcinogen. The list of carcinogens is very long and includes things like nickel, which is used in stainless steel. So you have spoons and forks being sold with warnings that they contain "chemicals known to the State of California to cause cancer". And businesses that are small and would be burdened by the cost of testing their products to make sure they don't contain those chemicals simply find it easier to just slap a label onto their product, knowing that people generally ignore the warnings.I used to buy scientific equipment at auctions and resell it on ebay. I bought some radiation detectors and put them on ebay. Some guy from a government nuclear agency started harassing me saying I needed a license for them because of a warning label on them. I removed the detectors from ebay and just figured I would contact the manufacturer to see if they would take them off my hands. I spoke to an engineer there who told me that after the Nuclear Regulatory Commission made them put those warning labels on their products, the company appealed the decision on the grounds that they contain less radioactive material than a smoke detector. They won the appeal. The engineer told me I could simply dispose of them in the trash if I wanted to.So the government errs on the side of caution, I guess, and sometimes makes a mess of things.

author: BillyO
author_rank: Super Contributor
timestamp: May 18, 2025, 08:00:44 pm
content: PCBs themselves are not nearly as toxic as we were lead to believe, however .. if exposed to high enough temperatures, or burned, they will release furans and dioxins, which are very bit as toxic as we are lead to believe.

author: calzap
author_rank: Frequent Contributor
timestamp: May 19, 2025, 07:10:42 am
content: Quote from: mehoff on May 18, 2025, 07:53:22 pmIt was California voters that passed proposition 65 with good intentions, but it turned out to be one of the stupidest and most useless propositions ever passed. In addition to the government, it allows individual citizens to sue manufacturers and sellers who fail to put a warning on their goods or in their store that one of over 1000 carcinogens may be present. As a consequence, the warning is nearly universal and universally ignored. I've seen the warning even on food items. A manufacturer or seller is foolish not to use the warning even if they a pretty sure no carcinogens are present because the warning will have almost no effect on sales. But if a listed carcinogen is present and someone notices, then a lawsuit may follow.Mike

author: Haenk
author_rank: Super Contributor
timestamp: May 19, 2025, 12:51:55 pm
content: Quote from: BillyO on May 18, 2025, 08:00:44 pmI don't think instant toxity is the major problem with these - it's the accumulation in your body which leads to cancer and slow death. Your really don't want thatThough exposure to larger amounts can lead to significant short-term health issues as well. And you don't want that either.So it's best to just avoid these - just in case - and have them professionally waste treated (i.e. burnt at very high temperatures). Don't just toss them into the bin.

author: MariuszD
author_rank: Regular Contributor
timestamp: May 19, 2025, 03:42:53 pm
content: This is interesting piece of old technology. Give us more photos. In modern ultrasonic cleaner there is no reason for kV rated capacitor. Is it made with vacuum tubes?To repair something it is necessary to know how it works. Show us more. What components are used? How they are connected?Old devices can have service manuals with schematics. Can you find it?Capacitor plague happened 20 years ago, different capacitors, different era. After capacitor plague some people think that that nothing other than a capacitor can fail.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: May 19, 2025, 10:40:20 pm
content: Billy is quite correct. The PCB itself is not necessarily the toxic part of the oil. There are other seemingly unavoidable chemicals in the oil that cause harm over a long period of exposure, so the oil should be avoided. If it is confined inside the can, that is good confinement.Quote

author: mehoff
author_rank: Newbie
timestamp: May 20, 2025, 01:56:06 am
content: I'm sorry, but it has been disposed of.

author: Zero999
author_rank: Super Contributor
timestamp: May 20, 2025, 12:31:09 pm
content: Quote from: mehoff on May 20, 2025, 01:56:06 amI think you made the right decision. Please update the original post, to save a newcomer from reading through. Don't delete, just append EDIT: I have now disposed of it, so it's unnecessary.