GW Instek GOS-6112 Power Transformer Repair

[4s6tmp]

Hi all,

My GOS-6112 went kaput due to a power surge. The 230V 400mA fuse, MOV, and finally the Transformer Primary were blown. I was reluctant to rewind it as it would almost cost me the price of the entire scope. Thus I was looking for a replacement transformer.



At last, I wrote to GW Instek Taiwan. After some back and forth emails, they sent me this datasheet of this Transformer P/N GOS-6103-PT .
https://drive.google.com/file/d/1D93kymphGQkTa4NEuIaPETEYmKxPj2W_/view?usp=sharing

The 0V Primary tap is an open circuit in my transformer. I am now hopeful that it could be this thermal fuse that has been blown.
 

Have you ever ripped off a GOS-6103-PT? Is the thermal fuse eacily accessible? This seems to have been soaked in Shellac. Feels very rigid and strong. 

[fourtytwo42]

I have had thermal fuses open from current surges but that's a very expensive custom trafo so if your gonna do the job be EXTREMELY careful, I saw a post recently where some fool tried to open a trafo by slashing it with a knife and completely destroyed it! Think of it as open heart surgery!

It's most likely on the side with the primary wires. On that side very carefully peel back the copper (remember it has to be resoldered afterwards, then each layer of insulation (WITHOUT CUTTING ANY WINDING WIRES UNDER IT) cutting alternate sides so the cuts wont overlap when it is re-assembled. Keep following that 0V lead and if you are lucky you will find it jointed to a bare wire or something other than winding wire, that will be a lead of the cutout.  Hopefully you can gently prise the cutout out of its enfolding layers of insulation and replace it (dont be tempted to just short it out).

Good luck

[nctnico]

If you look at the pictures you'll see the primary windings seem to be under the secondary windings making it impossible to get to the thermal fuse. I'd use the  working primary windings (perhaps add a 230V to 115V transformer if necessary).