Sony STR-DE945 transformer teardown

[repair-it]

Just wondering if anyone has any experience doing a non-destructive tear down on a transformer like this one. I'm trying to get to the thermal fuse and was hoping it was possible. So far, not much success this appears to have been immersed in varnish during manufacturing. The plastic core housing appears to have been inserted from both sides when built, just not sure how to take apart without snapping the plastic core into pieces.

thanks,
rich

[repair-it]

Re: Sony STR-DE945 transformer teardown

UPDATE: ok I think I figured this out. There is a weld strip on top that goes across all of the plates and the mount on the bottom has 4 spot welds that attach to the plates. I think if I take a grinder to it, I should be able to 'crack it open'. Gonna give it a try.

[goodpsusearch]

Re: Sony STR-DE945 transformer teardown

Please post some pictures of it, it would be really helpful for future reference

[repair-it]

Re: Sony STR-DE945 transformer teardown

Sorry, didn't think there would be much interest in this, see attached. I could only locate 2 of these transformers online, used, and replaced this one with one I purchased online from Canada. Did some re-soldering on receiver front panel as there were several cracked joints causing it to flicker on & off, unit is working again. My hope was to repair this transformer and maybe someone would buy it from me since these are very rare .... and heavy. I'm hoping that the windings are still ok, will test once I get it opened.

Still work in progress, will post updates, doing a video as well as I go, with the hope I can restore this transformer in the end.

[R_J]

Re: Sony STR-DE945 transformer teardown

Grinding the lamination welds still won't give you access to the thermal fuse it is there.
In your first post it looks like you opened the secondary side of the transformer not the primary side.

[repair-it]

Re: Sony STR-DE945 transformer teardown

I haven't worked on one of these before so all I've had to go on is this video: https://youtu.be/BpTERBlryBo

This seemed liked a similar transformer. Either way, it needs to come apart to get to the fuse. The video doesn't show much of the process but I'd like to gain some knowledge on these through this experience. I have some time right now to play around with it and am using this project for a learning experience .... I hope and not just wasting time.

The orange & white wires are primary.

[R_J]

Re: Sony STR-DE945 transformer teardown

Do the primary wires enter this side of the transformer?

[repair-it]

Re: Sony STR-DE945 transformer teardown

This is a pic of opposite side.

[repair-it]

Re: Sony STR-DE945 transformer teardown

UPDATE: ok, so I was able to figure out how to open the transformer up.

It required grinding welds on top and bottom. The bottom mount(see previous pics), which was welded, needed to be drilled out and removed to access the bottom weld. I used a 3/8 bit but a 5/16 would have been better. The laminates were welded because the 'I' laminates are all stacked together and not staggered. The 'E' laminates are all stacked together as well and butt to the 'I's which is why they were welded together.

Once all that was done, I tapped on the top of the transformer with a hammer several times and the 'I' laminates separated as a solid piece from the 'E' laminates. The 'E' laminates were difficult to loosen but after several good taps to the center of the bobbin from the hammer, they eventually freed up.

Now I have the bobbin exposed but haven't figure out how to separate what looks like two sections so I can get access to the primary. I broke it in 2 places trying to see if I could pry it loose to access the primary coil. I believe that is the thermal fuse in the primary winding, center of last pic.

[repair-it]

Re: Sony STR-DE945 transformer teardown

UPDATE: So after all this - unfortunately, this particular transformer is not really repairable in a practical sense. It has multiple windings on what looks to be a single bobbin, which would require undoing to get to the thermal fuse and then re-doing the windings that were removed. I am calling this a 'no-fix' for that reason, however there is some recyclable copper wrapped around the bobbin, not a total waste of time for this project. Here's a link which gives an idea of how this type of transformer was assembled.

https://youtu.be/s6NyTprQCBI

The project transformer was 20 years old and doesn't look like it was intended to be repaired the way it was assembled, expected fix was to just buy another, good luck finding a replacement today. Hope that this project may help someone know what they are getting into.

[petehall347]

Re: Sony STR-DE945 transformer teardown

is this where the thermal connects ?

[repair-it]

Re: Sony STR-DE945 transformer teardown

Yes, I believe it is buried in there - that lead looks like it belongs to a thermal fuse. I haven't gone any further taking it apart, doing as time allows.

[repair-it]

Re: Sony STR-DE945 transformer teardown

The ultimate end to this attempted repair. Thermal fuse was open. Will recycle the windings.

See attached pics. Unless this transformer was not replaceable, I would not attempt a repair as it requires destructive dismantling to access the thermal fuse and it would be difficult to do without damage to the windings. I learned something new and hope this info/experience is helpful to someone else. A torroidal might be a better replacement option.