I'm doing some service and updating on a solid state preamp/power amp pair soon. The person I'm doing the work for is specifically interested in longevity. Would it be a good idea to pull the PCBs and inspect both sides for cracked solder joints? Should I reflow the joints just to be on the safe side?
If it is RoHS lead free solder, dry joints are common.
Also common fault on Sony and Sansui.
European boutique makes, it is normal, do not bother to inspect, just do it. Do not worry about their reputation...B&O were junk. Many others too.
Use leaded solder, re flow ALL joints, replace capacitors if needed, spray all mechanical contacts - switches, pots, etc....
Then test it, once final, clean off all flux residue with a soft wire brush, then use pure iso alcohol to really clean, check for residue with a magnifying glass. Clean again if needed.
After it is clean, apply insulating varnish / PCB spray coat on the track side as insurance.
That should be enough.
Also common fault on Sony and Sansui.
European boutique makes, it is normal, do not bother to inspect, just do it. Do not worry about their reputation...B&O were junk. Many others too.
Use leaded solder, re flow ALL joints, replace capacitors if needed, spray all mechanical contacts - switches, pots, etc....
Then test it, once final, clean off all flux residue with a soft wire brush, then use pure iso alcohol to really clean, check for residue with a magnifying glass. Clean again if needed.
After it is clean, apply insulating varnish / PCB spray coat on the track side as insurance.
That should be enough.
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Yes, or steel, glass fiber, something as stiff as a 'hard' grade toothbrush, but it must not leave conductive residue on the tracks.
Material, and pressure are both important.
If you are able to, get a fiberglass brush, they are pretty common.
I use brass, because I had one lying around. And another in fiberglass...
Material, and pressure are both important.
If you are able to, get a fiberglass brush, they are pretty common.
I use brass, because I had one lying around. And another in fiberglass...
This
No need at all to remove boards and blanket solder willy nilly , a careful and close inspection of the various boards under a good strong light and a loupe will tell if areas need rework or not.
Then either leave it well alone or attend to the positively indentifed problem areas..... even more so if the user reports no actual problems found in operation.
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No ! - the bottom obviously
You can ID the potential hot spots from the top though.
Ultimately it depends on the model in front of you, some manufacturers make it easy to get boards out, some have access panels to gain access to the bulk of the main board.
Problem areas include hot spots as mentioned (components near heat sinks ), run it up for half an hour and you’ll soon see where they are..
No point in removing boards with just chips on them, rarely get drys, other areas to check are board to board connectors , not wire connectors.
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I did mention pressure and experience using a brush...
Some amps need the board to be removed to get at the track side.
It would be good if you mention make and model of the unit you intend to work on.
Get the service manual, and do a search, it might have been done earlier by others. And many makers had a dud model, with known issues, check that.
And you say longevity, so maybe it is working well right now, and you want to do the equivalent of a car wash and lube / adjustment job?
Some amps need the board to be removed to get at the track side.
It would be good if you mention make and model of the unit you intend to work on.
Get the service manual, and do a search, it might have been done earlier by others. And many makers had a dud model, with known issues, check that.
And you say longevity, so maybe it is working well right now, and you want to do the equivalent of a car wash and lube / adjustment job?
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It’s a Hafler DH-110. I’ve read some service accounts from people. There’s the electrolytic to change. Apparently there’s a pair of transistors in the muting circuit that go bad and cause channel imbalance or no output, so I’m going to replace those. One guy mentioned the voltage regulators get pretty hot, so I’m getting new ones and beefing up the heat sinks on them. No mention of cold solder joints, but I’ll take a look at least. Clean all the pots. There’s two ribbon cables and people suggest cleaning the plug pins on those.
I made the mistake of using ISO alcohol to the clean the pots, the carbon track deteriorated and It was a centre tap pot which was very hard to replace. I now use Deoxit D5 for pots & switches. Oxidized 6.5mm phono & phono sockets, I curl up very fine grade sandpaper 1200 grit to polish the inner contacts. Seems quicker to use a cordless drill for polishing. All in all, no more crackling regardless turning knobs or sockets.
Best to desolder the suspect solder joints and apply new solder. ISO alcohol cleaning with a small thin 1" paint brush with the bristles cut shortly works for me.
If you want to be lazy cleaning the whole PCB, Electrolube safewash is very good, cover foam all over the PCB (removed from chassis) and rinse in water and dry with a hair dryer.
Have fun!