Andromeda

TUTORIAL Repairing 12v transformer 7684

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Evening All,

I had a transformer that was only outputting around +/- 7.5V from the speed controller output. I had a dig around online and found conflicting information on how to open the unit up, includung an old 2011 post here on Eurobricks.

One person said to drill them out, another said to push them in, and another said not to pull them, I pulled them!

They are round pegs with two plastic barbs at the end, well after pulling them the barbs were fairly non existant. I have left an entry mark down the side of each hole and the pegs have a dent were my 120 degree desoldering tool was pushed in and pulled them out, not ideal for reselling!

Not sure how drilling would go as the pegs seemed easy to rotate in their holes, but If you were to drill in 2mm with a 3.7mm bit then you would be able to push them in.

I tested both caps for ESR and correct value, ok, and both 1K resistors were fine. Outputs from Tx itself on full tilt gave 16.89 A.C. All of the diodes rectifying the speed output tested as conducting, but when the voltage was measured across each, one was dropping 6V. I relaced all four (located top right when you lift the cct) and they are 1N4003's.

Edit: The caps are 2.2uF, 400v @ 85 deg.C.

Here are a few pics to give you an idea:

dsc00692zp.th.jpg

dsc00693hh.th.jpg

dsc00694fc.th.jpg

dsc00695mw.th.jpg

dsc00690jv.th.jpg

dsc00699oy.th.jpg

dsc00696ft.th.jpg

These were the fellows:

dsc00697eo.th.jpg

Any questions or comments welcome.

Edited by Andromeda

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