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Old 14th October 2007, 04:29 AM   #1
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Default drilling transformer mounting holes-bit broke!

I am almost finished with the restoration of a magnavox amp 83.

My last peice was the power transformer. I removed it and sanded the thick epoxy on the sides, however in the process of removing it , all four bolts snapped off in the transformer. I was able to get one out successfully, and the other two I drilled out.

However, the third i had almost drilled completly out...when the bit snapped!! I don't know how to get it out, I tried everything!

I also wanted to ask if it hurts the transformer to drill into it at all, because the mouting holes arent perfect... just enough to hold the transformer together and hold it to the chassis. It wont effect performance/hum will it?
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Old 15th October 2007, 08:38 PM   #2
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Maybe I am not following, but can you drill from the other side? Smaller hole then punch out the bit that busted off?

Your going to have a nightmare of a time trying to drill out a drill bit. No can do without some hardcore tools (that I am not familiar with).

Evan
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Old 15th October 2007, 09:39 PM   #3
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If you are talking about the type that has the bolts running through the laminations you do have a problem. Probably best to grind off the remaining head, chuck it up in a vise and try to pop it loose with a punch from the head side or drill it from that side. If its going to cause too much damage you can always remount it with the three remaining bolts, just dont tell anybody[????]
A machine shop could get it out but that will cost you a few bucks.
Regards, Bill
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Old 17th October 2007, 03:02 AM   #4
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I was able to break the bit up with a punch. One of my holes drilled a tad off when I went through, but I don't think that will affect overall performance at all. It holds it together and holds it to the chassis.

As for the hole I got the bit stuck in... the laminations expanded during all that banging and drilling.. at least a few mm! I chucked it in a vice and tighened it up as best I could and stuck a bolt through it to hold it. I don't think any of the epoxy potting came out of the cracks. Will I have problems with the transformer buzzing or should it be ok?
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Old 17th October 2007, 01:02 PM   #5
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You probably lost a little transfer efficiency and it might buzz a little. You should mix up some epoxy and pour it into the hole with the bolt in it and tighten all four nuts til it sets up. Grease up the threaded end of the bolt so you dont epoxy the nut to it. That should work but you never know til its done.
Good luck, Bill
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Old 27th October 2007, 03:36 AM   #6
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well I have it mounted to the amp. Seems to be working fine and looks tons better than it did. I have had a problem with it buzzing, but if I press on it in certain areas I can get it go away.. I think a peice of potting chipped off and is bouncing around in there between the bobbin and the bell cover.

Does seem to get a bit hot, but I think that should be normal for what it is.I am going to set up a bucking transformer in front of it to keep the voltage down to around the 117 v it was designed for.
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