Actually I didn't say they have leaked, but I do say that they could only have leaked from the bottom, but you can't tell. This does appear to be what happened to some of the capacitors I had on the other PSU I repaired recently, although again I can't be sure. However there *is* something on the board to which dirt and little shards from the heat sinks appears to be sticking at least a bit, but perhaps it is just dirt that has absorbed humidity. Certainly the board has been in some kind of humid environment, the case itself is quite rusty in places. So it is probably more like someone else suggested, and not capacitor leakage but a humid/damp storage environment. Either way, does anyone know if those heatsinks are a standard part? If not I am not averse to replacing them with something else, but it would be nice to keep things as original as possible. Regards Rob From: dwight [mailto:dkelvey at hotmail.com] Sent: 23 October 2017 23:10 To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> Subject: Re: Cleaning and Restoring a Badly Corroded PSU I don't see why you have assumed that one of the capacitors has leaked. The corrosion could have come from water or condensation onto the board. I don't see any corrosion on the components. Dwight _____ From: cctalk <cctalk-bounces at classiccmp.org <mailto:cctalk-bounces at classiccmp.org> > on behalf of Rob Jarratt via cctalk <cctalk at classiccmp.org <mailto:cctalk at classiccmp.org> > Sent: Monday, October 23, 2017 1:45:42 PM To: General Discussion: On-Topic and Off-Topic Posts Subject: Cleaning and Restoring a Badly Corroded PSU I am now looking at the H7826 PSU that came with a TURBOchannel Extender. It looks like there may have been capacitor leakage and some heatsinks will need to be replaced. I have posted pictures here: https://robs-old-computers.com/2017/10/23/corroded-h7826-power-supply/ So two questions: 1. Any suggestion on how to clean the board? Some of the corners are a bit inaccessible to reach with just a cotton bud and isopropyl. 2. Do those heat sinks have a particular name/spec that I can search for? Thanks Rob

have another your photos, Hello Maciej, That 4700uF/10V capacitor is really hard to remove, it seem to be connected to large planes on both sides, which suck all the heat away. I have a suspicion that it may have leaked from the underside as the area around it is certainly quite dirty in a way that suggest the dirt has stuck to something. Did you manage to remove this part without destroying it and without damaging the board? Regards Rob

On Sat, 28 Oct 2017, Maciej W. Rozycki wrote: On second thoughts if solder has corroded, which may well be the case given the overall state of your PSU, then you will have troubles melting it, because, obviously, oxides and other compounds which would have formed won't usually melt as easily as metal. In that case I suggest trying mechanical means to remove the contamination and then applying extra solder to increase its mass in the joint before trying to undo it. I do remember having problems with handling corroded joints next to leaked capacitors in my H7874 PSUs, even though those specific joints didn't have any way to lose heat easily. HTH, Maciej

Thanks Maciej, really, pen. Your technique has to be better than mine because I used an iron, a suction desoldering station and a flux pen. However, after multiple attempts throughout the day, I finally succeeded a short while ago. I am not sure what is wrong with my technique. twice the where Indeed, there is no interference from the capacitor on that daughter board, that didn't cause me a problem. you voltage). I will have to dig out the replacements I bought a while ago, I can't remember what I chose, but I generally get the ones with higher hour-temperature ratings. need to I wish you luck with that! In my case I have not actually tried powering it on yet, I really wanted to clean it up first as I am sure some of the bits off the heatsinks were likely to create some shorts and I am pretty sure some of these capacitors have leaked. By the way I just noticed a 15uF/25V one next to the fan connector. It isn't one of the SXF ones as far as I can tell, do you recall replacing it? Regards Rob

I have ordered the part now anyway. Whether I will replace it or not I don't know yet. I am told that ESR measurements are not enough to detect bad caps though, although I always replace ones with ESR that is at or close to the limit on the table printed on my meter. Regards Rob it? did leaking replacement for its capacitors correctly. I am of suspicious

I would remove the transformers before putting it in the wash. The big one doesn't look to be hermetically sealed. Dwight ________________________________ From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Phil Blundell via cctalk <cctalk at classiccmp.org> Sent: Monday, October 23, 2017 3:27:29 PM To: rob at jarratt.me.uk; Rob Jarratt; General Discussion: On-Topic and Off-Topic Posts Subject: Re: Cleaning and Restoring a Badly Corroded PSU On Mon, 2017-10-23 at 21:45 +0100, Rob Jarratt via cctalk wrote: Maybe the photos don't do justice to the full horror but it doesn't look all that bad from what you've posted. The heatsinks do look a bit corroded but, if they are aluminium (which I would guess they are from the photos) then this might just be dampness rather than anything more sinister. Aluminium does tend to rot a bit in prolonged contact with water, and if it is also in contact with steel then you get an electrolytic reaction which can be fairly ruinous. I doubt the heatsinks are a standard part you can buy off the shelf. They have a bit of a custom look about them. But, unless you are worried about authenticity of those parts, a standard heatsink from Farnell etc will work just fine. If you do want the authentic article then you might need to get some replacements machined. As for cleaning the board, given that it seems to be relatively low- tech I would probably be fairly comfortable putting it in the dishwasher on a shortish cycle. Then give it a bit of a rinse with deionised water and let it dry out. The caps don't look obviously leaky, and (unlike batteries) it doesn't seem to be common for capacitors to ooze their electrolyte without fairly evident physical distress. But replacing them is probably a good plan anyway! p.