Replacing axial caps. Can I use radial electrolytics? - Page 1
Forum section: electronics / beginners

author: Josepsp
author_rank: Contributor
timestamp: June 14, 2021, 09:47:41 am
content: Hi everyone.I have a few questions regarding axial capacitors replacement options. The blue ones shown in the picture, that might or might not be electrolytic. (yes, indeed, my actual knowledge level is that bad)- can they be safely replaced with radial ones? (of same or superior voltage off course)- if so, which would be the positive side?- Is there a better alternative? The values range from 15uF to 680 with voltages in the 6v3 - 25 range, but for a few 100V ones.I have a very limited budget and was planning to use cheap radial electrolytic, as I have a box with plenty of them.If it were only a couple I might try to buy proper axial ones, but we're talking about 40-50 cap and I am on a tight budget. This repair isn't probably going to end well, so I would prefer to go chep and, eventually replace again all of them with quality ones if the device returns to life.BTW, I am working on trying to bring back to life an old Philips PM3323 oscilloscope rescued, literally, from the kerb 15 years ago that has been gathering dust in the attic since. I was hoping to fix it to be my first oscilloscope but it is so overwhelmingly complex that I finally got a cheap Hantek and this is a "lets try" protect.The mighty machine:I have already changed 36 smd electrolytic caps. So far, so good, but I'm hitting a wall understanding the axial ones, as the polarity confuses me.edit: title typo

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 14, 2021, 09:51:38 am
content: Sure, put one lead in, and just add a jumper wire to connect the far lead. Maybe add a glob of glue (preferably electronics safe silicone or the like?) to anchor it so it's not wobbly.Tim

author: Josepsp
author_rank: Contributor
timestamp: June 14, 2021, 10:05:28 am
content: Quote from: T3sl4co1l on June 14, 2021, 09:51:38 amThanks!Mechanically I am not that concerned. Most of them are way smaller so I can arrange a radial one vertically or resting on its side. I have done a few tests and they seem to stay nicely in place. Wobbling shouldn't be a problem in this static device, although I don't know if some of them could produce noise and require silicone. I have read about that in some posts here.My biggest trouble goes on the electric side, especially regarding the polarity of the ones shown in the picture. Is there a positive? Searching about similar axial capacitors read about the band being positive, but the + signs in the middle are confusing.

author: David Hess
author_rank: Super Contributor
timestamp: June 14, 2021, 10:19:53 pm
content: Quote from: Josepsp on June 14, 2021, 09:47:41 amThose are definitely aluminum electrolytic capacitors.QuoteRadial parts can be used as replacements for axial parts. Either one lead can be folded back, or often better is to attach the leads at more opportune spots on the board as shown in my example below.QuoteOn an axial aluminum electrolytic capacitor, the crimped side with the rubber seal is the positive side. In your photograph, the top parts is positive on the left.QuoteReplacement with radial parts is usually the best option. Higher voltage parts can be used for convenience.

author: BrokenYugo
author_rank: Super Contributor
timestamp: June 15, 2021, 04:01:24 am
content: I wouldn't mess with them unless you have good reason to suspect one. A box full of cheap caps of unknown specs are not necessarily an improvement over 30+ year old vintage ones.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 15, 2021, 03:34:59 pm
content: Why are you replacing them?

author: tooki
author_rank: Super Contributor
timestamp: June 15, 2021, 04:05:40 pm
content: If you’re replacing them, why not replace them with… drumroll please… axial caps? Several manufacturers still make them. In fact, that’s a Philips scope, so made with Philips caps, which are now Vishay, so you should be able to get something very similar to the original.

author: Josepsp
author_rank: Contributor
timestamp: June 15, 2021, 08:26:15 pm
content: Quote from: David Hess on June 14, 2021, 10:19:53 pmThanks a lot for the detailed answer. It's been a busy day and I've been unable to check the thread.I finally used yesterday late my few remaining neurones to cross the actual board with the diagram in the service manual to find the positive side, and I spend most of the day today swapping caps... 40 or 50, I've lost track (and in a bad way).I tried to start the oscilloscope afterwards and the first iteration has been quite explosive. Literally. Two caps hit the ceiling. I guess as a result of having mixed polarity in one of the boards. The ones that exploded were correctly oriented but near to a few others that weren't. Also, the rated voltages in the original parts were quite close to the actual voltages carried by the tracks after checking the schematics. Being the new ones crappy Aliexpress might have helped to the catastrophic failure. I have changed them for other rated higher, just in case.Lastly, I tried again to start the device and this time it carried the self-test giving a blinking light at the end and shutting himself down immediately, leaving a high pitch wining in the power supply area. The third time I tried to start it has blown the fuse, and right now there's a short to ground somewhere (not in the CRT high-volt area, as I have it in a test arrangement that leaves that detached).I guess that will need a different thread if I get stuck, although in the two power supply boards carrying mains I used trustworthy X2 and High voltage caps to replace some RIFA that didn't look ok.

author: Josepsp
author_rank: Contributor
timestamp: June 15, 2021, 09:10:56 pm
content: Quote from: Siwastaja on June 15, 2021, 03:34:59 pmThe oscilloscope had several problems, both on the display and on the acquisition side. A few topics here discussing the model addressed the second area replacing 32 o 36 SMD electrolytic caps in one board. I did that last week and apparently helped, as I was able to glimpse son signals were before there was only white noise.All the guys on those threads also went straightforward to replace all the axial caps. I assume everyone knows better than me, so I thought that would be the way to go. Just to be sure I tested ESR and it was really high in 90% of the caps.In the area of the mains voltages I only changed 3 RIFAs that were scary and a few other low-voltage rated axials that had very high resistance, just in case that could be the reason for the issues in the CRT, as one of the boards has the flyback. (it didn´t solve the issue)Quote from: BrokenYugo on June 15, 2021, 04:01:24 amI am afraid you're absolutely right, looking at the resultsQuote from: tooki on June 15, 2021, 04:05:40 pmI'm a cheap bastard. ;PLongest story: I have little budget to drop here and I felt since the beginning I was quite unlikely to succeed in the repair, as I have almost no idea what I'm doing. Not as bad as electrocuting myself, but this thing is way too complex for my current or future skill level.I had the box of caps here, so I thought just dropping them in place (after checking values) could do the trick.It wasn´t aimed to be a final repair. I was hoping to reach if not a working device, at least a "good enough to hope is completely fixable" state, so I could eventually put together the money to get the proper parts and do a fine job. Time is the thing I have to spare right now, so doing everything again doesn´t bother me.I wasn´t going to really use it anyway. I recently put all my savings in the cheapest Hantek so this is just a long term project. I just wanted (and still want) to see it working. Hopefully, I wouldn´t have done any serious damage.

author: Josepsp
author_rank: Contributor
timestamp: June 15, 2021, 09:28:42 pm
content: So thanks again for the answers guys.I´m dropping a few pics of the work in progress:the starting point. Only grabbing noise and way out of range in focus, very wrong size in H and V and flickering/changing size badly constantly, this was the only readable pic I got:This one after replacing the 33 SMD electrolytics, and RIFA and a few others in the power boards: (that was the most readable pic, the screen was equally messy)Here exposing some of the boards to work with the axials (those 4 had to get out):working notes for every step:and the exploding caps. I mounted the two next to them with reversed polarity:edit: English

author: RayRay
author_rank: Frequent Contributor
timestamp: June 15, 2021, 10:36:15 pm
content: Last pic doesn't look right at all to me! Where's the other leg of each capacitor? It looks like you've just cut it away, or am I missing something? Doesn't look right (given the fact you're replacing axial with radial) And also, generic jwco vent caps? Seriously? You need proper, low ESR caps from a reputable brand here, not generic Chinese caps.

author: Josepsp
author_rank: Contributor
timestamp: June 16, 2021, 06:32:09 am
content: Quote from: RayRay on June 15, 2021, 10:36:15 pmI need a lot of proper things mate, but I have to deal with the crappy stuff I can afford or I already have, as mentioned previously.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 16, 2021, 12:57:39 pm
content: Just don't buy electrolytic capacitors from Aliexpress. Definitely don't ruin a scope by changing all electrolytic capacitors, 95-100% of which are likely just OK, to counterfeit crap.Even proper ones are dirt cheap, you need to pay some shipping costs with proper distributors but if you are replacing such large number of parts you should be able to get over the minimum free shipping limit especially if you are an electronics hobbyist and can combine something else you need on the same order.Getting good parts (i.e., no counterfeits, no scams) is essential for a hobbyist.

author: RayRay
author_rank: Frequent Contributor
timestamp: June 16, 2021, 01:05:03 pm
content: Quote from: Josepsp on June 16, 2021, 06:32:09 amGlad to see the legs were just hidden. But back to the choice of capacitors, those generic ones you're using wouldn't last long, and could potentially even cause damage to the circuit in the long run. Capacitors aren't overly expensive, and you could easily get better ones from TME or LCSC. Up to you, just know that laziness has it's price!

author: madires
author_rank: Super Contributor
timestamp: June 16, 2021, 01:28:15 pm
content: Quote from: BrokenYugo on June 15, 2021, 04:01:24 amThe old blue Philips electrolytics are known to go bad after 20 to 30 years.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 16, 2021, 01:50:21 pm
content: Quote from: madires on June 16, 2021, 01:28:15 pmAre they? I have used dozens of those, new old stock, and they seem to be just fine after 30 years or more. I have actually measured a bunch and ESR was top notch. Can't say the same about every capacitor.

author: madires
author_rank: Super Contributor
timestamp: June 16, 2021, 02:27:38 pm
content: I came across multiple of them while repairing stuff and a while ago I had to throw away a few hundred NOS (smaller values around 2.2 - 100 µF).

author: David Hess
author_rank: Super Contributor
timestamp: June 16, 2021, 03:02:32 pm
content: Quote from: tooki on June 15, 2021, 04:05:40 pmAxial capacitors cost a lot more, and have poorer availability and variety.

author: Josepsp
author_rank: Contributor
timestamp: June 16, 2021, 05:38:43 pm
content: Quote from: RayRay on June 16, 2021, 01:05:03 pmIt is not laziness. I am in fact doubling the workload, as if this repair succeeds I totally will recap again everything with branded caps... if I get a bloody job some decade.It is plain and simple cheapness. I can try my best to fix the thing with the stuff I can afford and if I fail it's going back to storage for a while without having put money in it. As simple as that.I have purchased proper caps every now and then, and here they are bloody expensive. I don't have any contacts, there is a single place where I live that shells electronic parts and they charge 0.50€ for a bloody resistor. They are a no-go for me. Online catalogs aren´t cheap.Add the fact that I know nothing and can´tdifferentiate a good brand from a bad one. Sure, Philips, Nichikom and a few others ring a bell, but I have no criteria to go for good affordable options. These cheap caps I am using are bad material, but I bought many of those on Amazon hoping they would be slightly better. Obviously, they are not.If we were talking about a couple of caps or a dozen I would do it, but we´re adding 80+ caps. Close to 120 if I go for the >50v which I haven't touched. That´s money that I would rather save for some other stuff, or even better tools, as everything I have is the cheapest crap.edit: typos & English

author: Josepsp
author_rank: Contributor
timestamp: June 16, 2021, 05:48:13 pm
content: Just for clarification: I tested every single cap I removed for ESR, and all of them but maybe 3 tested very high values, way above the ones in the chart of maximum values my tester has.Regarding capacity, the smd ones were plainly dead. The axials still had some, although many of them had gone seriously down. The RIFA I didn´t even test. Dave scared me enough in the video talking about them.I also tested every new cap I put there. Approximately 50% of the box gave a lower value than expected, so in many cases, I went for the next value (choosing an already decreased one). I did the same for voltages, going for larger ones than the ones they were replacing (but for a few ones like the ones that exploded). The ESR for all of the new radials was 00 or very low.

author: tooki
author_rank: Super Contributor
timestamp: June 17, 2021, 04:46:03 pm
content: Quote from: Josepsp on June 15, 2021, 09:10:56 pmThere are places to use cheap components, but test gear isn't one of them if you ask me. You want to be able to depend on your test gear. In the end, "expensive" capacitors are still cheap in the grand scheme of things.Quote from: Josepsp on June 15, 2021, 09:10:56 pmYeah, you really want to avoid having to resolder the joints over and over. Each time there is a risk of direct damage (like a damaged solder pad) or indirect damage (like ESD damage to a component elsewhere on the board). For a single component to see if it brings the device back to life, temporarily installing a cheap component is viable. But I wouldn't do a whole untargeted recap using cheap ones.

author: Josepsp
author_rank: Contributor
timestamp: June 17, 2021, 05:09:48 pm
content: Quote from: tooki on June 17, 2021, 04:46:03 pmThis is going to read sacrilegious, but I don't see this unit as test gear in my context. I know it really is, but for me is more a fascinating piece of vintage equipment. Using it hasn't been the plan since I grasped the complexity of the project and the null chances to have it properly calibrated, as I lack any reference material.As I bought the Hantek I just wanted to have it displaying properly and safe from further leakages (there was some damage from the dead smd caps). The plan was to keep it as a curiosity or maybe backup equipment for specific tasks where the analogue display could have better use than the cheap new one.Doing an untargeted recap has been my humble uninformed approach, as I lack any base to do better. I am a proper noob that is just starting this year reading schemas and datasheets and trying to develop some skills repairing vintage stuff which I'm enthusiastic about. It was a blind shot trying to at least discard high ESR caps being the root of the issues.I now realize it has been a huge mistake to go that way, but on the bright side, I am now quite familiar with the different boards and the service manual, which at first were utterly terrifying. Baby steps. Hopefully, I wouldn't have caused any permanent damage. Fingers crossed.I haven't thrown the towel yet, but I'm procrastinating for a while focusing on a couple of apparently easier projects I was also struggling with, just to recover some spirit.Thanks again everyone for the support guysedit: grammar, again

author: tooki
author_rank: Super Contributor
timestamp: June 17, 2021, 10:38:22 pm
content: I doubt you’ve damaged it, either, since it is working. It’s only a matter ofriskany time one performs surgery on a device.And you will learn! If you stick around here, it’s basically inevitable!

author: Josepsp
author_rank: Contributor
timestamp: June 18, 2021, 06:40:17 am
content: Quote from: tooki on June 17, 2021, 10:38:22 pmI'm afraid it isn't working anymore. Somewhere up there in my long answers (I'm useless being concise), I mention that it doesn't boot anymore. After fixing the blown caps and checking again the polarity of the others, it did a full start without display image to drop a blinking error led but then immediately went off and never started again.There's a clear high-pitch whine coming from the power area, and I suspect something has gone wrong with the very early replacements in there (Rifas and a few axials). Probably unrelated to the last complete recap and exploded caps, as the last time it worked when I took the pic with the blurry sine wave, it needed two tries to start and some whine was perceptible during the early start.I'm extremely glad to read about the inevitability of learning. I drifted to electronics converging from two other ends of the hobby repair spectrum: a high level of abstraction from IT where I'm stuck with a bunch of old sick computers in the hardware side, and the bare automotive electrics repairs where things are simple and straightforward but I was stepping into simple circuits. This is honestly awesome, both the field and the forum.

author: tooki
author_rank: Super Contributor
timestamp: June 18, 2021, 10:46:50 am
content: Oops, I did miss that it won’t boot.As for cars: theyused to besimple. One of the biggest changes in cars over the past 30 years or so is the electronics. They’ve gone from “simple” ECUs controlling simple 12V lines to monster integrated systems running on networks with encryption all over the place. (There are some very sound reasons for locking down at least critical systems, but it’s a PITA for third party repair, including DIY.)

author: Josepsp
author_rank: Contributor
timestamp: June 18, 2021, 12:12:00 pm
content: Quote from: tooki on June 18, 2021, 10:46:50 amBeing an issue located in the power supply I feel slightly more confident to perform diagnostics. Somehow I am more familiar with how they work and have even had some success in easy repairs. The original malformed CRT display and signal acquisition issue were way out of my comfort zone.My experience in automotive carries from the last century, always with second-hand stuff and in the last years has been focused on motorbikes, so I've been lucky enough to spare the recent exponential increase in complexity and the drift towards software and DRM.Beyond the ECU the electrics in the vehicles I've worked with were ridiculously simple and easy to follow, and even those ECUs were to some extent understandable and hackable for the average Joe. My own motorbike's (2012) injection has a Frankenstein solution to fix a burnt ECU output using a 555 and a few passives patch board inside a relay. One of the works I'm most proud of and probably the early one that pushed me towards this field.The definitive stimulus went from my other passion and also career choice which is IT. Both my old 386 and 486 early computers developed serious hardware problems, which going below certain layers are impossible to diagnose with the tools a regular IT guy has, so here I am: learning electronics to fill the gaps.

author: wizard69
author_rank: Super Contributor
timestamp: June 20, 2021, 04:05:41 am
content: If you have actually tested the caps and they are bad, I wouldn't put old caps back in the unit. That is buy new ones and further buy good quality ones. I'm rather surprised that they are all bad so you might want to check you testing hardware.As for this scope as a piece of test equipment I think you need a change of attitude. if you get it to work it can be useful for years even if it is never calibrated. Depending upon what you are doing simply seeing the wave form can be very enlightening.As for the cost of components, have you looked for EU distributors that will ship to Spain? That is a get on a web site, order the components and have them shipped in. Charging what amounts to $1 a resistor is a rip off if that is what your local supplier is doing. As for local employment conditions, it sounds like there is a business opportunity selling electronic components. Otherwise I have to agree with others, stay off EBay and the China sites and stick with high quality caps.