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Old 25 March 2010, 13:59   #1
Precious & fragile things

Join Date: Feb 2009
Location: Victoria, Australia
Posts: 1,946
Caps, When They Should Be Changed

In various threads you read about dying hardware, the two quick fixes are leaking battery and capacitors, but the quick fix of capacitors get bandied about fairly often. - This article talks about the capacitor plague, when and how

So when should you think about replacing capacitors?

I have just taken the main board out of my A2000, its serial is 000184 and it was manufactured in Hong Kong, a REV 6.2 most likely made in 1990/1991, give or take a few years, which means the caps are somewhere around 20 years old. Before I dismantled it, there were no obvious faults, it's been pulled apart to have the case modified for a PC supply, fixing of the second CF slot and a custom adaption of the audio connectors. With such an opportunity I am replacing all of the electrolytic capacitors with good quality parts, replacing all of them at the same time. The reasons for this should be obvious, but if they are not, the reasons are;

1. By replacing all the capacitors at the same time you know that you very much lower the risk of having a failure in the future due to a cap you should have replaced, thereby saving yourself a dollar or two at the time.

2. With the mainboard being completely removed from the frame, capacitor replacement is far easier for through-hole parts.

With Amiga models using SMD type capacitors, ie. the aluminium round style, these are far more likely to fail than standard electrolytics, they have a shorter life span. You can easily tell if these parts fail by two simple tests;

1. Visual test, you look around the capacitor for a greasy substance, or a perpetual 'wet look'.

2. Smell it, electrolyte, when leaking out of these capacitors has a smell much like well matured urine or fishy type smell.

Lower voltage capacitors are more likely to die earlier, along with lower values, so a 10uF 16V capacitor is more likely to fail earlier than a 220uF 25V capacitor, this was highlighted on my A4000 mainboard and A3640, I replaced all of the A3640 caps in 2005 and only now am I having some issues with the A4000 mainboard. You could say that I didn't live up to my first rule at not changing all the caps at the same time, truth be told, I wasn't planning on using the A4000 at the time but I could see that the A3640 caps were greasy.

Power supply issues are another common problem with Amiga units, keeping the original brick style PS units is fine, if you're purely interested in aesthetics, like some people on this forum, but if it doesn't matter, a PC PSU of ***GOOD*** reputation is a far better bet. Think like this, if you replace your Amiga PSU with a PC PSU, by spending an extra $20 - $50 now, you are most likely saving your valuable Amiga hardware from being accidently fried due to a poor quality PSU that you saved that initial $20 - $50 on, cold comfort when you have $500 - $2,000 worth of fried Amiga hardware sitting in front of you. The problem with the older supplies is that they were never designed to power the multitude of add-ons that some people like to put in their Amigas. My A2000 supply didn't like two hard drives, two floppies, GVP '030 and a CD Burner, would work about 40% of the time as an example.

Give Amigamaniac's site a visit if you would like the adapter cables for all classic Amiga hardware PC PSU conversions, he provides them with a jumper setup which acts as a crude on / off switch, but with a little forethought and electronic skill, adding a nice little box and a power switch is very easy, I used a simple toggle switch mounted on the holes at the front of the A2000 as an on / off switch. I'll be posting pictures of this setup soon, Chain is waiting with baited breath

Everyone will add their own 2 cents worth to this thread but all I hope is that it can provide some information to people about what and how, also perhaps stopping people from 'automatically' blaming capacitors.

Ian Stedman ( Stedy ) and Zetr0 both have guides towards power supply replacement and adaption, if people are interested. Rkauer is the advocate for capacitor swapping and I don't like to see him crying

Last edited by Loedown; 27 March 2010 at 10:25.
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