Author Topic: Replacing axial caps. Can I use radial electrolytics?  (Read 1100 times)

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Offline Josepsp

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Replacing axial caps. Can I use radial electrolytics?
« on: June 14, 2021, 09:47:41 am »
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





« Last Edit: June 14, 2021, 09:52:05 am by Josepsp »
 

Online T3sl4co1l

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Re: Replacing axial caps. Can I use radial electrolitics?
« Reply #1 on: June 14, 2021, 09:51:38 am »
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.

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Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolitics?
« Reply #2 on: June 14, 2021, 10:05:28 am »
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
Thanks!
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.

 

Offline David Hess

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #3 on: June 14, 2021, 10:19:53 pm »
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)

Those are definitely aluminum electrolytic capacitors.

Quote
can they be safely replaced with radial ones? (of same or superior voltage off course)

Radial 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.

Quote
- if so, which would be the positive side?

On 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.

Quote
- 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.

Replacement with radial parts is usually the best option.  Higher voltage parts can be used for convenience.
 

Online BrokenYugo

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #4 on: June 15, 2021, 04:01:24 am »
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.
 
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Offline Siwastaja

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #5 on: June 15, 2021, 03:34:59 pm »
Why are you replacing them?
 

Online tooki

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #6 on: June 15, 2021, 04:05:40 pm »
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.
 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #7 on: June 15, 2021, 08:26:15 pm »
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)

Those are definitely aluminum electrolytic capacitors.

Quote
can they be safely replaced with radial ones? (of same or superior voltage off course)

Radial 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.

Quote
- if so, which would be the positive side?

On 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.

Quote
- 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.

Replacement with radial parts is usually the best option.  Higher voltage parts can be used for convenience.

Thanks 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.

 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #8 on: June 15, 2021, 09:10:56 pm »
Why are you replacing them?
The 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)


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.
I am afraid you're absolutely right, looking at the results :(


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.
I'm a cheap bastard. ;P

Longest 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.
 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #9 on: June 15, 2021, 09:28:42 pm »
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  :palm::

edit: English
« Last Edit: June 15, 2021, 09:32:05 pm by Josepsp »
 
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Offline RayRay

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #10 on: June 15, 2021, 10:36:15 pm »
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.
 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #11 on: June 16, 2021, 06:32:09 am »
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.


I 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.
 

Offline Siwastaja

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #12 on: June 16, 2021, 12:57:39 pm »
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.
 
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Offline RayRay

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #13 on: June 16, 2021, 01:05:03 pm »
I 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.
Glad 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!
 

Offline madires

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #14 on: June 16, 2021, 01:28:15 pm »
I wouldn't mess with them unless you have good reason to suspect one.

The old blue Philips electrolytics are known to go bad after 20 to 30 years.
 

Offline Siwastaja

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #15 on: June 16, 2021, 01:50:21 pm »
I wouldn't mess with them unless you have good reason to suspect one.

The old blue Philips electrolytics are known to go bad after 20 to 30 years.

Are 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.
 

Offline madires

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #16 on: June 16, 2021, 02:27:38 pm »
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).
 

Offline David Hess

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #17 on: June 16, 2021, 03:02:32 pm »
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.

Axial capacitors cost a lot more, and have poorer availability and variety.
 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #18 on: June 16, 2021, 05:38:43 pm »
I 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.
Glad 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!
It 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´t differentiate 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
« Last Edit: June 16, 2021, 05:51:19 pm by Josepsp »
 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #19 on: June 16, 2021, 05:48:13 pm »
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.
 
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Online tooki

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #20 on: June 17, 2021, 04:46:03 pm »

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.
I'm a cheap bastard. ;P

Longest 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. 
There 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.


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.
Yeah, 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.
 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #21 on: June 17, 2021, 05:09:48 pm »
There 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.


Yeah, 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.
This 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 guys  :-+

edit: grammar, again
 
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Online tooki

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #22 on: June 17, 2021, 10:38:22 pm »
I doubt you’ve damaged it, either, since it is working. It’s only a matter of risk any time one performs surgery on a device. :)

And you will learn! If you stick around here, it’s basically inevitable!   >:D
 

Offline Josepsp

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #23 on: June 18, 2021, 06:40:17 am »
I doubt you’ve damaged it, either, since it is working. It’s only a matter of risk any time one performs surgery on a device. :)

And you will learn! If you stick around here, it’s basically inevitable!   >:D
I'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.  :-+
 

Online tooki

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Re: Replacing axial caps. Can I use radial electrolytics?
« Reply #24 on: June 18, 2021, 10:46:50 am »
Oops, I did miss that it won’t boot. :(

As for cars: they used to be simple. 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.)
 


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