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Old 17th Jan 2024, 3:04 pm   #1
Takapuna
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Join Date: Jul 2009
Location: Derby, Derbyshire, UK.
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Default JVC HR-D860 Cap Leakage Damaged PCB

MODS: Whilst this is JVC HR-D860 model-specific, it might be equally at home in one of the more general sections?

I have read many comments regarding the damage that leaking electrolytics can do to a PCB and the surrounding area but this one is hard work. Two or three of the smoothers on the secondary side of the SMPS released fluid some time ago and the resulting damage is proving very difficult to clean.

The "good" news is that only a very small amount of track has been lost, but electrolyte has wet the component side of the board and leached its way down several component leads. It has not eaten the leads but has left one or two that have the appearance of having been (perfectly) de-soldered. In many other places the solder pool is either depleted or has taken on a crystalline dry-joint appearance. Whilst all this is relatively localised it means the resulting quality of many of the surrounding near-by connections is a cause for concern. There are plenty of good-looking connections remaining on the board but only at a distance from the damage.

The unit appears to use lead-free solder and this doesn't help the clean-up operation. I don't find lead-free solder as easy to work with as 60/40 and a trial replacement of the start-up capacitor on a clean part of the board still took a little more effort to produce nice looking joints. I’m using 60/40 solder as that is all I have.

The semi-crystallised joints are very difficult to de-solder. They refuse to melt easily when a tinned iron is placed on them as if there is no heat transfer. Adding extra flux and attempting to add 60/40 solder to the joint doesn’t help much. When I do manage to melt the joint, it rolls up into a ball much smaller than the apparent mass of material and comes away from the PCB land but not perfectly so. Components can then be extracted with difficulty. Trying a number "8" Weller Tip instead of as the usual "7" makes little difference.

I’ve removed all the electrolytics at the damaged end of the board and cleaned it with warm water and detergent followed by a rinse and then plenty of IPA and a stiff brush. The pads from where components have been removed need whetting with extra solder and then some solder wick and gentle abrasion from a glass fibre pen and re-tinning to stand a chance of making a good joint. The legs of components from the damaged area do not easily re-tin and need to be removed and abraded to clean them. This is slow laborious work and this VCR would either have been scrapped or waited for a doner PSU from another machine had it appeared on a repair bench where people need to earn a living. Fixing the PSU does not guarantee a working machine of course!

I will continue to work on it slowly, but wondered what other folks’ experiences of this are and if I’m missing any tricks that would make the process a little easier?

Thanks.

Phil
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Old 17th Jan 2024, 11:38 pm   #2
whaka54
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Default Re: JVC HR-D860 Cap Leakage Damaged PCB

some high activity rosin flux are more efficient to get oxidized joints to melt and pad cleaning.
those flux are conductive, good cleaning is really required.

so they're not recommended if smd IC's are in the area to clean, because trapped flux residue behind pins can cause a lot of troubles and even kill components.
but for thru hole, they can greatly help.
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Old 18th Jan 2024, 11:32 am   #3
Takapuna
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Default Re: JVC HR-D860 Cap Leakage Damaged PCB

Thanks whaka54.

I will try to get some high activity rosin flux. Will high activity flux in combination with my 60/40 cored solder be OK or should I find lead-free solder with high activity flux? Wondering if the rosin cored 60/40 might reduce the effectiveness.

The PCB is a standard single-sided one with no surface mounted components, so it should be easier to clean afterwards.

Regards,

Phil
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Old 19th Jan 2024, 6:07 pm   #4
whaka54
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Default Re: JVC HR-D860 Cap Leakage Damaged PCB

personnally i use leaded solder, i think it's 60/40 too.
maybe the flux contained in wire may reduce a bit it's activity, but not that much.
but you can fill your solder tip and let the flux "burn" before using the high activity one.
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Old 31st Jan 2024, 8:27 pm   #5
Takapuna
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Default Re: JVC HR-D860 Cap Leakage Damaged PCB

Good news.

Some high activity rosin flux mixed to a syrup with IPA has made the salvaging of this board much easier. As whaka54 stated it makes heat transfer into the affected joints much easier and makes tinning the pads easier too.

After removal, cleaning and replacement of nearly all of the components at the transformer secondary end of the board along with new electrolytics everywhere (excepting the mains reservoir) the power supply now works as it should.

The board has been thoroughly cleaned in a bath of IPA and dried. It has behaved itself when left powered for many hours and cycled on-off several times.
I need to choose some form of coating for the repaired area where there is now a significant amount of solder showing and much less lacquered track.

Now on to the mechanical service...including replacement of the 3.3uF capacitor on the head drum board.

Thanks again,

Phil
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Old 1st Feb 2024, 9:33 pm   #6
whaka54
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Default Re: JVC HR-D860 Cap Leakage Damaged PCB

hi,

not really than heat is better transfered (IPA will eat a lot to vaporize) but high activity flux contain acidic mixture which help to dissolve corrosion.
and that's why it's conductive and need to be cleaned after use.
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