bruce Posted July 25, 2014 Share Posted July 25, 2014 Today's job was repairing a radio mic pack that came back in with it's aerial separated from the body pack. It's a JTS unit - like most mic body packs the antenna is a pier of stiff wire a few inches long, which protrudes from the top. It's not detachable. On the board inside the unit, there's a little metal "box" with circular openings in the top and one side. The top has a round disc about 7mm diameter pressed into it. There's a similar cutout on the side, and the antenna mount is pressed in there. Popping out the top disc, there's a solder terminal inside. So repair looks straightforward. Press the aerial back into the housing, perhaps with a dab of superglue, solder the inner wire, press the top disc back in, job done. There's about 3mm of stranded wire protruding from the base of the aerial. Perfect length to reach the solder terminal. Only problem, I can't tin the end - I can't get the solder to "stick" to this bare wire. I've tried an ordinary iron and a gas iron, at full power. I've tried cleaning the wire with emery paper etc. I don't think it's lacquered or anything like that, although I could be wrong. Due to the design, stripping back the wire further isn't an option. Just using standard 60/40 multicore solder. I won't be back at work for a couple of weeks - if I was there, I'd probably have access to a selection of fluxes etc. Any suggestions? Link to comment Share on other sites More sharing options...
Jivemaster Posted July 25, 2014 Share Posted July 25, 2014 Bakers Fluid as flux has helped me before, as has some old tin lead solder. I found bakers fluid on the web for about £10 -old solder can be harder to find. Link to comment Share on other sites More sharing options...
DrV Posted July 25, 2014 Share Posted July 25, 2014 If you do use a really aggressive flux then be sure to wash off all the residue thoroughly as it will eventually find its way into places it shouldn't and cause corrosion damageDave Link to comment Share on other sites More sharing options...
simploerob Posted July 26, 2014 Share Posted July 26, 2014 You can still buy leaded soilder from most plumbing merchants. You will find stuff on the shelf but if you ask they normally hold the thin solder as well and a large selection of flux! Link to comment Share on other sites More sharing options...
Oldradiohand Posted July 26, 2014 Share Posted July 26, 2014 60/40 solder should be fine - it's the "old" recipe. I'm suspecting the wire is steel which takes a bit of tinning. A splash of Baker's fluid to tin the wire and then wash it off before soldering to the board should stop any corrosion problems and the tinned wire should solder fairly easily. Link to comment Share on other sites More sharing options...
Dmills Posted July 26, 2014 Share Posted July 26, 2014 One other trick if having real problems is to wrap the bundle of unsolderable strands in a strand of copper wire as a whipping and then solder to that.... Not ideal, but for this it will probably work. 73 Dan (Who remembers fitting Lemos to steel core lav cable, evil job). Link to comment Share on other sites More sharing options...
Bobbsy Posted July 29, 2014 Share Posted July 29, 2014 I had a similar problem last year fixing a radio mic (also a JTS for my son's school). In my case, I just gave up on the existing antenna and made my own--I had some stranded wire in a heavy, stiff jacket, did a back of an envelope calculation of the best length for the frequency then solder that other wire onto the internal connector. I covered the whole thing in heat shrink tubing to make it even stiffer, then another layer of one size bigger heat shrink as a strain relief at the base and another "lump" at the top so no copper protruded. I'm told it works better than the original but suspect they're just flattering me for the next time. Link to comment Share on other sites More sharing options...
bruce Posted July 29, 2014 Author Share Posted July 29, 2014 So, ordinary soldering flux made no difference. Plumbers flux also didn't help - but it was the "drinking water safe" type, not the more aggressive one that can be used on heating pipes. No Bakers at work - it disappeared in the last H&S/COSHH purge! But you can still buy it. Very frustrating - needing to buy a whole can of Bakers just for 1 wire! Might try the "whipping with a copper strand" trick next. Link to comment Share on other sites More sharing options...
timsabre Posted July 29, 2014 Share Posted July 29, 2014 Could it be steel or aluminium wire?You'll never solder to that - crimping is the only thing to do. Link to comment Share on other sites More sharing options...
bruce Posted July 29, 2014 Author Share Posted July 29, 2014 It's some sort of stiff, stranded wire. Don't know exactly what - there's only a few mm visible through the bush. It looks like it has been previously soldered. Link to comment Share on other sites More sharing options...
timmeh2 Posted July 29, 2014 Share Posted July 29, 2014 Hi You may find that the previous load of solder is of the silver variety. All the bestTimmeh Link to comment Share on other sites More sharing options...
bruce Posted July 30, 2014 Author Share Posted July 30, 2014 I tried Dan's suggestion of "whipping" the end with a strand of copper wire. Soldered with plenty of flux. Seems to have done the job. Thanks Link to comment Share on other sites More sharing options...
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