Sony Cmt-cp33md power transformer blown

[notallbad]

Power transformer has open circuit on the 230v primary side, its tapped for 115v too which is also open so most likely the thermal fuse has blown. It doesnt look like it would be possible to open it up to check the thermal fuse so looking to replace.
What are peoples thoughts on repair?
replace the one transformer with 2
replace like for like, though unlikely to find a direct replacement

[notallbad]

Re: Sony Cmt-cp33md power transformer blown

Looking at this it would seem its possible to bypass the open circuit thermal fuse on the transformer by simply forming a bridge.

Of course, the safety aspect will no longer exist but will at least allow me to power it up and operate the unit to test full functionality.

[R_J]

Re: Sony Cmt-cp33md power transformer blown

Yes you can bypass it, The power supply has an external fuse so if the primary IS shorted, that fuse would blow. In most cases the thermal fuse seems to be a bit under rated and after time just goes open.

[notallbad]

Re: Sony Cmt-cp33md power transformer blown

Ok so bypassed the thermal fuse but after a few seconds of the unit powered up and running the transformer does begin to overheat and smoke.
So guessing the transformer is definately shot?

[R_J]

Re: Sony Cmt-cp33md power transformer blown

It only takes one shorted turn and the transformer will do that.

[notallbad]

Re: Sony Cmt-cp33md power transformer blown

Managed to find a similar model unit with the same transformer inside.
Swapped it over and its all working again now.

[UNITRAX]

Re: Sony Cmt-cp33md power transformer blown

In which model did you find the matching transformer?
I had an adventure with the Sony TA-F210. Suddenly it stopped playing and started to throw sparks. It turned out that the transformer unsoldered itself from the pcb. I mean the primary winding pins were on fire. It's strange that the transformer survived and the amplifier probably still works.

[notallbad]

Re: Sony Cmt-cp33md power transformer blown

The original xfrm is a 1-435-386-11.
Found identical xfrm in a CMT-CP11 even though the service manual gives reference to a different part number (1-435-657-11),though I guess not knowing the history its possible its been replaced in the past.

The difference between the psu pcb is that the CMT-CP11 does not have the extra ribbon pin/cct Ac det, I believe. Hence why the xfrm was soldered out and not pcb swap.

The replacement xfrm primary read 630 ohm between pin 6 and/or C(ommon) and pin 2. And between pins 1 and 2 is 140 ohm, just for info.

The original was def shorted, read around 13 ohms between pins 2 and 6.