Archive for the 'Mods' Category

Welltech wireless headphones – batteries replacement

Published on March 2, 2012 in Equipment, Mods and Repairs. 1 Comment Tags: , .
Welltech FKH51

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 god 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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FT-1000D Noise Blanker Modification

Published on February 8, 2012 in Mods. 0 Comments Tags: , , , .

Opened up the ft-1000d today and discovered that the famous w8ji noise blanker modification was missing. Well, no need to dwell. Fired up the soldering iron, picked up three 1n4148’s and a 10k resistor and started to work the mod. And the modification went smooth as oil. The process can be seen in pictures below. I’m not going to discuss the technical detail of this mod, for this information please visit w8ji and n1eu. Oh yes, another thing I discovered was that the rig had the inrad roofing filter mod already installed, that was a nice surprise!

 

IF board area where the mod is going to be applyed

Connectors in the right corner removed for easier access.

Soldering diodes to connector J2001.

10k resistor soldered to ground lug and third diode soldered to TP2001.

Modification completed