I think we need the 22V for IC91 to work. Double check you have D91 the right way around and check the diode next to it is not shorted (was this replaced?). You should have continuity between R91 and R98 as you say - I think I need a pic of the underside of the board covering R98 to D91 and IC91. If you have a high voltage on R91 it could damage C92 - what voltage rating is C92? C92 could get very hot and even explode!!!!!!!!!!!!!!!!
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Actually I am getting continuity between R91 and R98, and I always checked for continuity between each pin I fitted (not the solder) and a distant point on the same track before trimming the pin. However this particular doesn’t always show up with continuity.
D91 and D93 are Ok, and D91 pointing same way as before. D93 was not replaced. Pic attached.
A pic of the underside in all its horror, together with approx the same area some weeks ago. The fact is I had a lot of problems getting solder hot enough to free the folded over part of the pin, and even to resolder yesterday. I’d get a small blob near the hole, but the next thing I knew I had a little ball bearing running around the boar – in fact just spotted a tiny one from the photo that I hadn’t cleared. I have a hotter iron on order and should be here in a day or two. I hope the damage is repairable.
C92 is 50v 22µF. So I’ve done something serious to let 100v get to it. I should have mentioned that there is no voltage at R93 next to R91. Could the two faults be connected?
Yes you are right it is a bit of a horror picture - the only option is to do some serious patching up. Please remove R91 and R93 clear solder from their holes and take another pic so I can formulate a plan - I am assuming you have more replacements for these resistors. I will probably need to show you the next step using a pic - I wonder if I will be able to post it?
Sorry, I forgot to say you should be sitting down with someone at hand with a cold sponge to mop your forehead before looking at my pics.
Looks like my new soldering iron arrives Thursday (from my normal electrical wholesaler). So, best wait until then to minimise further damage. And yes I have plenty of those resistors - ordered two of each before realsiing they came in packs of ten!
Thanks for, in the cir***stances, a measured response.
I would not have thought you would need a high power iron to work on the PSU board. I hope we can patch this up although it won't be pretty when we've finished. I am still hoping to see the box work but if was a cat it would be really short of lives by now. By the way the PSU board is only single sided (tracks on one side only and no internal ones) and does not have plated through holes and so solder will not be drawn into the holes. The cause of your difficult in soldering is due to damaged tracks and missing pads - nothing to solder to - the one leg of R91, for instance is surrounded by fibreglass and not copper.
I've got things to do tomorrow so do not expect quick replies.
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Pic attacheIMG_5020.jpgd.IMG_5020.jpg
Thanks I need to think about this.
I am beginning to think your soldering iron bit could be a problem - does solder stick to it? The first time you use a new bit you need to apply solder to it as it warms up so that you coat just the tip with solder this is very important otherwise you will struggle to solder with it. You need to keep the tip coated with solder at all times and remove excess solder and crap with a wet sponge (or just flick it off into a bin). If you have a spare bit perhaps it may be worth changing it. Modern bits are coated with iron and you are not meant to file them because you will remove the coating. If it is your only bit or if you are not worried about it's lifespan you can file the end down to the copper and then coat it with solder as it warms up. I will have to leave you to decide what's best.
Ah, that explains a few things. Yes, solder has been sticking to the tip. Will try the treatment before the next job. That’s assuming you think a repair can be done – fingers crossed.
Try this link - if I am allowed to post it - Moderators this is just a link to soldering tips.
_http://www.instructables.com/id/Soldering-101%3A-Lesson-1%3A-Tin-the-Tip/
Last edited by cosworth4x4; 19-04-2017 at 09:08 PM.
Long silence again – lots of distractions.
Pic of re-fitted C92. Not very happy with it. I had mislaid the new cps, so had to use the old one, and that meant I had to hold it in one hand. I used my new iron which boasts a ceramic tip. I put a lot of solder on, but a lot of it seems to have stayed on the iron tip. I’ve now found the new caps, so perhaps I should have another go.
As regards the power connector, Pin 3 had retracted and in doing so had gone at an angle so it wasn’t lined up with the others. I’ve bent it a little, and have been able to fix the connector, so perhaps OK. Pic of connector and the soldering attached. The dark patch is where the flux has dried.
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I think for now we should concentrate on the motherboard because the PSU is such a mess we need to get the soldering right before we attempt repairing it.
On the motherboard pin3 does look better but still not as good as I would like. Also the flux residue and other debris is a concern, although zooming in on your pics makes things look worse than they probably are. Having said that we cannot afford for any of the debris to cause shorts - no more bangs!
See if you can clean things up using an old toothbrush and some alcohol based fluid, perhaps meths. You can buy PCB cleaner but if you have something suitable we can save time and money.
Alcohol is also usable as a flux, some fluxes are over 90% alcohol, so perhaps you can try to use it instead of the flux to see if you can get the solder to flow better. If you compare the pins you have not soldered you will see how much neater they are with the solder flowed to the bottom of the pin and no stray bits left further up the pin. Pins 1 to 7 need attention and also the last 3 pins but concentrate on a few pins until you get good results and perhaps only add a small amount of solder.
If you have an old/scrap circuit board it may be useful to practice on that first, remove solder and re-solder. Good luck and let me know how you get on.
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