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Desoldering problem with vintage pioneer recap project
Desoldering problem with vintage pioneer recap project
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Old 2nd July 2012, 07:25 PM   #1
jazzzman is offline jazzzman  United States
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Default Desoldering problem with vintage pioneer recap project

I am recapping a Pioneer turntable circa 1974-1977. I am having a dickens of a time melting and removing the old solder from the board to remove the original capacitors. I have attached a picture of the bottom of the PSU board that I started on. The motor board has everything closer together so I would like to get my technique down before starting that one.

I first tried using the desolder braid, I tried the M.G Chemicals brand (no clean and then the regular) and then the Radio Shack brand with no luck. I set the iron to 600 degrees, then 650, and finally 700 (I was reluctant go any higher than that). The solder would not melt with the braid between the solder and the iron tip. What temperature should I be using?

Removing the braid and applying the tip directly to the joint, at 700 degrees the solder melted. I used one of those spring operated one handed vacuum pumps to remove a few capacitors, but this operation is not as clean as I think I should be able to do with the braid.

I tried applying a bit of new solder to the joint, I tried putting extra flux on the braid (but I was using an old flux pen that may or may not have actually applied any additional flux). Does anyone have any suggestions? I do not know why it is so hard to melt the old solder. Is that typical? Should I increase the heat? or maybe buy a bottle of flux and try putting more on the braid?

Thanks for any help on this.
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File Type: jpg Bottom of PSU board before cap change.jpg (746.9 KB, 151 views)
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Old 2nd July 2012, 07:37 PM   #2
sofaspud is offline sofaspud  United States
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I would use just the iron to melt the solder and pull out the cap. Then use sucker, braid, and/or a thump on the table to clear away the solder for the reinstall. To me, tip temp isn't so important if contact time is adjusted accordingly.
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Old 2nd July 2012, 11:39 PM   #3
Simon B is offline Simon B  United Kingdom
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Stripped scrap flexible wire rather than braid, the end dipped in rosin flux. Solder flows better through this and it's available in a variety of sizes.

A little rosin flux to the joint to be de-soldered, with a cocktail stick.

Dry tissue and moist (not sodden) sponge in the wells of the iron stand, for a clean tip, and an appropriate width bit on the iron.

Good initial thermal contact is key to desoldering, start off with just the bit to the joint. Fresh flux helps this. As the old solder melts, roll the bit sideways to make room, insert the braid/wire then roll the tip back on to maximise heat transfer. As the solder flows move the braid/wire along to speed the soaking up, then disengage. Trim the braid/wire as needed, it's an unnecessary heatsink otherwise.

Do this to all the leads of a component, then extract it with a touch of the iron where needed. Save the vacuum pump for clearing through holes where necessary.
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Old 3rd July 2012, 04:38 AM   #4
dangus is offline dangus  Canada
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Desoldering problem with vintage pioneer recap project
When I'm desoldering something, I nearly always apply some fresh fluxcore solder.

Then the classic Edsyn DS017 Soldapullt to remove most of the solder. Braid if I need to get the pads really clean, but with braid you have to keep cutting off chunks as it becomes saturated. Also, I think the brand and type of braid is important: finer strands may wick better.

Last edited by dangus; 3rd July 2012 at 04:40 AM.
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Old 3rd July 2012, 03:12 PM   #5
jazzzman is offline jazzzman  United States
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Thank you all for the help. I plan to try again this weekend.
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Old 3rd July 2012, 05:19 PM   #6
macboy is offline macboy  Canada
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When I have problems melting old solder joints, I add more fresh rosin core solder (60/40 or 63/37). Not a little, but a lot of it. This always helps. I think that the hard-to-melt solder might be some alloy that melts at a higher temp. Mixing it with the low temp stuff (63/37 is the lowest common solder alloy IIRC) makes it easier to melt. The side effects of extra flux and the removal of surface oxidation also help a lot. I will often use the sucker to remove the initial big blob, then follow up with braid, otherwise you'll go through lots of braid.
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Old 4th July 2012, 12:45 PM   #7
indianajo is offline indianajo  United States
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I have a lot of irons that heat but the tip does not. Sometimes this can be repaired by removing the tip and dropping solder down in the hole to improve heat flow, but not always.
I've got a Weller WP25 iron that works pretty well now, but if there are more than 4 20 gauge wires on a joint (old tube equipment) the iron doesn't have enough wattage. Oh, the WP25 is modified with a 7/32" inch flat end screwdriver tip. The pointy tip sold with the iron is only useful for tiny microelectronics.
I've got an 80 watt weller from Home D**** with a big wedge tip that won't melt solder at all. And various R**** S**** irons that melted solder only the first month.
To save money I use the scrap stranded wire dipped in flux to soak up old solder, but an iron with good heat flow will melt solder through the commercial braid. I don't like solder suckers, they mostly burn up the tip when I used them. If the end of the part lead is bent over, it helps to save the PCB by removing the solder before trying to bend the lead up.
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Last edited by indianajo; 4th July 2012 at 12:50 PM.
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