Sony RDR-HXD890 - Is this salvageable from water damage?

[HwAoRrDk]

Today I got a call from my mother: "The TV's not working! There's no picture and it says 'not tuned' on every single channel". TV seemed to be fine, just zero signal level. In addition to the TV, she has a DVD/HDD recorder as per thread title: a Sony RDR-HXD890. The aerial signal passes through it first before it hits the TV.

Upon further investigation, I find a crusty, corroded connector on the end of the aerial's coax cable. Hmm, that's odd. I replace the connector on the end of the coax. When I go to plug everything back in, I see that the RDR-HXD890's 'In' socket looked a bit crusty too, but on closer examination, I spied what looked to be something brown and gunky in the gap between the chassis and the socket. Uh-oh! I think I'd better open 'er up and take a look...

This is what I found:






Does anyone think there's any chance of cleaning this up and saving it? It appears to me that none of the components on the board itself are damaged, but I am doubtful about the state of a bunch of vias in several places; worried they may have corroded away to nothing. I'm also assuming the tuner module itself is toast - will probably crack the can to check - but that might be replaceable. The underside of the board is fine.

I'm slightly mystified how exactly water has found its way into the unit. I suspect it was through the coax aerial cable itself. This particular coax is of the type that has a hollow insulator, so it could easily wick down the cable, and the cable does come straight in from outside (no wall socket ) so there's plenty of scope for water to get in somewhere along the cable.

[james_s]

Wow that's a mess.

I've saved equipment that was pretty seriously corroded by battery leakage so I'd say there is hope, but it's a question of how much effort do you want to spend on it? Scrub it in the sink with something like Simple Green and a scrub brush, then rinse with clean water and let it dry. Look closely for corroded off pins, traces and vias.

[HwAoRrDk]

I popped the top off the metal can of the tuner module, but while there's no noticeable damage to what's visible, I suspect the underside of the internal board will be quite bad. But, I won't be able find out unless I de-solder the whole module.



I found that replacement tuner modules are actually listed as an official spare part (part no. 1-693-772-11), and can be purchased for around £20-40. So, perhaps if the board is okay, then the prognosis is looking better.

Unless anyone has any better suggestions, I think I'll try cleaning the board as suggested with distilled water, and then maybe try and de-solder the tuner module.

[james_s]

I would be inclined to look for an entire board on ebay if cleaning that one doesn't work. It wouldn't surprise me if one or more vias are corroded away, severing portions of the circuit.

Never seen water run down coax like that but I can see how it could happen.

[HwAoRrDk]

I cleaned the board last night. Scrubbed with a toothbrush with warm soapy water, then rinsed off with distilled water. I put it in the oven afterwards at 60C for about 30 mins to dry.

It came out better than I expected. All the vias appear to be intact (although I suppose only a continuity check will tell for sure - but my meter's probes aren't small and sharp enough to make proper contact with these small vias though ). There are a couple here and there that still have some white gunk in them, but they are only stitching vias on the ground plane, so not critical I think.

The only component damage I can see is that there are three zero-ohm resistors that were right next to the tuner module, linking two ground planes, that appear to have lost their tin plating on the end caps. I can always touch those up with a bit of solder and they should be fine.

Today I de-soldered the tuner module (which wasn't as difficult as I thought it'd be ) and whipped the bottom cover off.




Quite the mess there! However, upon closer inspection, everything still seems to be in place, so I might try giving this a clean too and see how it turns out.

[tablatronix]

Make sure your you put a drip loop outside on that coax also where it enters the house, in case it was from outside of the cable, not internal. coax acting like a hose is an interesting failure mode I will say.

[sokoloff]

In addition to the drip loop, you could use a run (or just a segment if it's too much hassle) of gel-filled coax to substantially block internal water migration.

[HwAoRrDk]

IT WORKS!!!

Did the same cleaning on the tuner module, and it came out looking quite reasonable. None of the components inside appeared to actually be corroded - just covered in brown crusty residue - and the only crustiness still on any components after cleaning I think was just leftover flux residue from the original manufacture.

So I soldered it back on to the board, re-assembled the machine and tried it out. Was able to successfully tune channels again, as well as pass through to the TV.

I was thinking that perhaps the brown residue was from the tuner module's metal can, but seeing as I was able to take an abrasive pad (i.e. dish cleaner) to it and it removed the brown staining to reveal clean, still-plated metal underneath leads me to think all this gunk maybe came from either the corroded coax connector or from the cable itself. Or perhaps something further upstream.

Definitely going to get the offending coax run replaced, and will make sure there is a drip loop put in on the new cable. Thanks for the suggestion.

[Gyro]

Water in the aerial cable used to be a common problem, not so much these days for some reason.

You'll find that the plastic cover or grommet on the TV aerial itself is either missing, cracked or leaking - water gets in and runs down the open channels in the insulation between the inner and the braid and out of the plug.

Yes, you definitely need a new run of cable, you probably also need a replacement TV aerial as there will be corrosion in the connection box too - I'm quite surprised it still works at all on a digital terrestrial signal. Make sure that the cable entry and lid on the aerial are fully sealed.


P.S. Well done on the repair! 

[james_s]

Nice job 

I'm pretty hard core when it comes to repairing things most people would write off, and even I was questioning whether there was reasonable hope of success there.