Recapping an ST board - is it worth?

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Did you ever find a faulty electrolytic capacitor on the ST motherboard?

Yes
9
45%
No
11
55%
 
Total votes: 20

tzok
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Recapping an ST board - is it worth?

Postby tzok » Sat Jun 09, 2018 8:53 am

Have you ever found an faulty electrolytic capacitor on the ST board? I haven't - either on the board, nor on the PSU. According to my experience these WANG'S CAPs were high quality, and all still, after 30 years, are up to their specs.

What is your experience in this matter?

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Re: Recapping an ST board - is it worth?

Postby Gaiyan » Sat Jun 09, 2018 9:18 am

It's only worth it if you succeed. Is it worth attempting? If you're having problems that could be related to caps, sure. If you don't know what you're doing, when to prioritize in ESR, when increased capacitance vs original is better, then no.

I've fixed dead PSUs with new capacitors but problem could have been something else that got fixed with soldering new caps. Like a bad solder connection.
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Re: Recapping an ST board - is it worth?

Postby Gaiyan » Sat Jun 09, 2018 9:58 am

To answer the other question "Did you ever find a faulty electrolytic capacitor on the ST motherboard?", it depends on the definition of faulty.

ESR gets worse over time on electrolytic capacitors. There's no way around it. So a 30 yo cap has a higher ESR than it did when it was installed. In that sense it is faulty. But if the higher ESR has no negative effect on the circuit it can't be considered faulty.

Same goes for capacitance. And many more characteristics.

So my answer is; I have not ever come across a single faulty capacitor on an Atari motherboard that was the sole cause of a major problem or malfunction.

I do not know, however, after changing caps, whether or not I have fixed stability issues that may or may not have been present.
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Re: Recapping an ST board - is it worth?

Postby Atarieterno » Sat Jun 09, 2018 10:09 am

I have not changed any capacitor on the motherboard.
Even the power supplies were still working, but in the STe I changed it to a modern PSU and in the Mega STe and TT I changed all the capacitors, for safety reasons according to the advice of the experts.

Fuente de STe (original).jpg


Fuente eXxos en mi STe.jpg


Old capacitors (Mega STe - TT).jpg
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Re: Recapping an ST board - is it worth?

Postby 1024MAK » Mon Jun 11, 2018 7:24 am

Electrolytic capacitors have a limited life. The manufacturers rate them at a specified number of hours when run at their rated maximum working temperature (often 85C, longer life types are rated for 105C).

How long they actually last is variable, as it depends on a number of factors. The main reasons being internal heating due to ripple currents, the temperature of the air surrounding them (that is, the air temperature inside the machine / PSU), radiated or conducted heat from any nearby components that run hot (if applicable), number of hours of use, quality of the capacitor, how conservative the working voltage rating is compared to the actual voltage the capacitors are being run at.

Assuming electrolytic capacitors are not abused, the normal failure mode at first, is for the equivalent series resistance (ESR) to increase. This does not significantly change the capacitance, but increases the impedance. This affects the circuit the capacitor is in. To the rest of the circuit, the effective value of the capacitor become far more frequently dependent. When used for smoothing and decoupling, or coupling applications, it will no longer be effective at higher frequencies.

As the capacitor continues to age, loss of electrolyte causes the capacity to drop. It may still be within it's tolerance at first. But as it's condition gets worse, so the rate of degradation increases. If there is more than one capacitor in parallel, the failure of one can cause the next capacitor to have to 'work harder' and so that one may fail soon.

A system that contains degraded capacitors may well work some of the time, but operation may become erratic, possibly with unexplained restarts / resets, or malfunctions when using power hungry sub-systems.

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Re: Recapping an ST board - is it worth?

Postby dlfrsilver » Mon Jun 11, 2018 9:09 am

tzok wrote:Have you ever found an faulty electrolytic capacitor on the ST board? I haven't - either on the board, nor on the PSU. According to my experience these WANG'S CAPs were high quality, and all still, after 30 years, are up to their specs.

What is your experience in this matter?


Are you aware that WANG'S CAPs is a pure poo 3rd grade Taiwanese brand of capacitors ? I don't even know for a start why Atari installed such junk inside their computers instead of using Rubycon, shoei or panasonic capacitors.

check the site called Bad capacitors, they have listed the poo capacitors companies, and guess what, Wang's caps are in ! :lol: :lol:

Those have to be removed and replaced, since they had a lower life span than 1st quality grade capacitors like the ones i cited above.

Just to illustrate, in my ST machines, once i recapped them (removed the Wang's caps junk caps), by panasonic and nichicon, which are doing a way better job than their old counterparts, the display was then way clearer and brighter than before, and the noticeable dim i got on screen each time the ST accessed the floppy drive disappeared.

Atari only used good quality caps on some ST series, but not all unfortunately, this to cut their cost.
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Re: Recapping an ST board - is it worth?

Postby mlynn1974 » Mon Jun 11, 2018 9:06 pm

I think it is worth it to recap your power supply if you want to keep your Atari running. I had a 20 year old epoxy filled Spectrum power supply go up in smoke and was glad it didn't damage my Speccy.

I don't know if Wang capacitors were that bad. The Bad Capacitors web site was, I thought, in response to the millions of bad caps that were made in the early 2000s due to the cheap caps using the stolen Rubycon formula the plagued the PC industry for a decade. Maybe Wang were at that point bad.

I've had one ST power supply that failed and I got a replacement and binned the old power supply. I didn't know it could be reconditioned. The capacitors certainly weren't bulging but I didn't know of anyone locally that could repair it.

The thing is that most STs are now over 30 years old or are coming up for 30 years old, and that's not bad for a computer using components that will eventually fail. It's nice that there are alternative power supplies available now.
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Re: Recapping an ST board - is it worth?

Postby dlfrsilver » Tue Jun 12, 2018 8:03 am

mlynn1974 wrote:I think it is worth it to recap your power supply if you want to keep your Atari running. I had a 20 year old epoxy filled Spectrum power supply go up in smoke and was glad it didn't damage my Speccy.

I don't know if Wang capacitors were that bad. The Bad Capacitors web site was, I thought, in response to the millions of bad caps that were made in the early 2000s due to the cheap caps using the stolen Rubycon formula the plagued the PC industry for a decade. Maybe Wang were at that point bad.

I've had one ST power supply that failed and I got a replacement and binned the old power supply. I didn't know it could be reconditioned. The capacitors certainly weren't bulging but I didn't know of anyone locally that could repair it.

The thing is that most STs are now over 30 years old or are coming up for 30 years old, and that's not bad for a computer using components that will eventually fail. It's nice that there are alternative power supplies available now.


Bad Caps forum lists the companies making crap capacitors, it's not related to the early 2000's capacitors problems.

the CapXon capacitors you can also find in some ST PSUs are also junk. they leak from the under and not from the top of the caps. You can only see it when you disolder them from the PSU.
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Re: Recapping an ST board - is it worth?

Postby tzok » Tue Jun 12, 2018 5:41 pm

I've actually checked not only the capacity of de-soldered caps, but also ESR and leakage current. For the tested units, they were all well in specs. Actually their ESR was better than some brand new generic Chinese LowESR 105*C rated equivalents.

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Re: Recapping an ST board - is it worth?

Postby dlfrsilver » Fri Jun 15, 2018 7:11 am

tzok wrote:I've actually checked not only the capacity of de-soldered caps, but also ESR and leakage current. For the tested units, they were all well in specs. Actually their ESR was better than some brand new generic Chinese LowESR 105*C rated equivalents.


anyway, capacitors are parts made to make the machine go out of order. Once they dry, they can make short circuits, which will in turn do damages on the hardware.

Capacitors life span for good ones are 25 years. Bad capacitors or 3rd grade ones life span is shorted. So yes, in order to not get any problems, just change them, and you will be safe. Don't wait for them to fail on you.
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Re: Recapping an ST board - is it worth?

Postby kcr2000 » Sat Jun 16, 2018 9:17 pm

Well, I have a lot STs and other Ataris and way more went through my hands. None of my Ataris has bad capacitors, neither on the PSU nor the board. I am with Atari since 1994 I guess ;-) and it's really been very few times, I have seen a bad PSU due to capacitors. On the board probably never... at least I don't recall having seen that at all. So much for the bad quality.
Remember, those machines are now around 30 years old! I'm sure they were not produced for longliveness but according to my expierience they do very well ;-)
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