I’ve got these cheap but good working wireless headphones branded Welltech 40699/FKH51a.
After several years of use the two AAA NiMH Rechargeable Batteries dies and I replace them with new ones. But hey, they will not recharge, what is wrong? Having a closer look at the headphones I discover that the battery cases have a protective device to prevent non-rechargeable batteries getting charged. This device is a simple contact spring that has to be grounded to the battery minus potential to enable recharging. So the solution was to remove some of the insulation material at the bottom of the batteries, and now the headphones again are recharging the batteries.
I have also done a small modification to the base unit. I have removed the small internal wire antenna and fed the signal to an external sma connector. This enables use of a better antenna which improves coverage when moving around. A simple antenna for the 850 or 900 Mhz GSM bands works good for this unit which operates on the 860 Mhz LPD band.
Here are some pix…
Battery holder. Upper left: Safety contact spring.
insulation prevents grounding of contact spring.
Bottom insulation removed from battery.
Modified battery on the right
External antenna connector mod
Thanks for the info ! i’d changed my batteries but he wont charge sow i thought the headphone was broke, stupid protective thingy :p thanks !!
This was doing my head in so many thanks.
Glad to help.
cheers!
Congratulations. Your electronic “teach” is wonderful. My welltech is alredy working. Thank you!!!!
THANKS, YOU HAVE JUST SAVED ME 25 QUID I WAS ABOUT TO BIN THEM
MANY THANKS, BRIAN
Hi – I had just replaced a wire to battery terminal that had corroded and gone o/c, caused by a leaking battery. Then fitted batteries that had been charged on a separate charger. All worked fine EXCEPT it did not charge. Fortunately thought of looking for manual on www – saw your advice – all working fine now! Thanks a 10**6! John in Scotland.
somebody know the schematic of the Welltech wireless headphones?
Thank you very much for your effort and sharing with us your findings! I really like these headphones!
(mainly because they are compatible with other brand, but same frequency transmitters). I have one transmitter connected to my TV, and one to my PC (on different channels), so I can change the “source” with a single button on my headphones. 🙂
Thanks again!:)
Zoltan from Hungary
Thank you very much for the tip. After a long time not using them I have put them back to life thanks to your advice 😉
Thank you very much man!!! wery simple and very neccesary info!!!
Dima, Ukraine, 2014
Fantastic info. And the extra mile with the antenna replacement. Cheap at half the price!
If I may impose on your knowledge further… I assume that you replaced the cable coming out of the ‘audio in’ with this?
Many thanks
Thank you ! You saved my day with this insulation thing I hadn’t noticed !