Sark 110 battery temperature sensor.

[Dave Baxter]

Hi.

I've been given a "Faulty" Sark 110 by a friend who said he could never make it work.

It would power up "briefly" then shutdown.

I charged it for an hour, and then it would run for a while.  Nice piece of kit, seems to work very well.

However, knowing what LiPo cell's can be like, I opened the casing (friend had it for some time, so well out of warranty) to find the cell that was glued to the back cover, obscuring it's identification marks.

I also found loose in the casing, what looks like a small thermistor, just floating loose.

The battery was removed and investigated, and actually found to be good.  (Takes a charge using an external charger, without warming up and no swelling.)

I'd refit it to the instrument, but what to do with the thermistor?   Where should it be connected to?   I can't find any schematics for the Sark 110, and there are no obvious signs on the PCB where it might have come from.

This "Thermistor" is a small black bead, about 1.8mm dia, on the end of two short wires, also black insulated, some 12.5mm long.  (No exposed conductor at the free ends though.)

Replacing the battery if needed is no problem, but I need to know where to reconnect this thermistor to.   Assuming, it's a battery protection component.

Regards to All.

Dave (G8KBV.)

[Steven Andros]

Hi Dave,

I've repaired a few of these beauties, and as far as I can tell, there isn't a battery temp sensor, but without a full schematic there's no way to know with certainty.

You might try a full board assessment with a microscope, a strong magnifying glass or even your phone. You may discover the mounting point.
You Might also try contacting Melchor - with a photo of the part. Perhaps he can identify it and tell you where it's supposed to go. 

According to the Sark-110 website:  info at sark110.com

Naturally, you'll need to fix it.

I have a battery on the way from China. Once it arrives, I can send you a good photo (if needed) of the board. Perhaps that will prove useful.

If push comes to shove, you might consider sending it to me.

Cheers & 73 - Steve KG4LJB

[k3gau Dave]

GE Dave,

You might want to go to the SARK110 site and download the SARK110  Vector Impedance Antenna Analyzer Application Notes.  It has lots of info about the use and operation as well as info on the parts including the battery / replacement.  I just did a quick scan of that info and didn't see anything about a temperature sensor, etc. 

Good Luck

Dave K3GAU

On Tuesday, February 11, 2025 at 5:12:42 PM UTC-5 g8kb...@googlemail.com wrote:

[John G3PQA]

Dave,  I have repaired a few also and never seen a sensor. I you want to send it to me I could have a quick look to compare to see if anything loose and try my battery in it if you like.  QTHR.

Its worth the effort of repair because there are still few rivals for HF field use, IMO.

(I note your call is not listed anywhere?)

73

John