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Horizontal x-former

9/22/1998 5:16 AM
Horizontal x-former
How would I go about mounting a Horizontal PT?
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9/22/1998 8:06 AM

You mean the kind that is going to need  
a big square hole in the chassis so the  
one side can poke thru, right?  
You can drill the four corner holes of  
the square, and use a hacksaw, metal cutters,  
files etc. to make it a square hole...  
... OR, you can get some long standoffs  
and longer bolts and mount the whole thing  
above the chassis.  
... Or, you can do like I did once and just  
tape the thing in place :-)  
... Whit
9/22/1998 8:51 AM
Dave H.

"... Or, you can do like I did once and just  
tape the thing in place :-"
I once removed an old 19" chassis from a rack here at work and when I put it down on itís side there was a grinding crunching noise as the massive PT crashed to the bottom of the box smashing boards and ripping out wires as it fell. It had been fixed to the chassis with double sided tape !  
9/22/1998 9:44 AM

... that's why I always use good quality  
duct tape when assembling amps ;-)  
... Whit
9/22/1998 6:59 PM
Reid Kneeland

>... that's why I always use good quality  
duct tape when assembling amps ;-)  
Hey, don't skimp! Use fiberglass strapping tape. :-)
10/1/1998 6:14 AM

C'mon guys, enter the 90's! How about some of those wonderful new industrial superglue adhesives out now?  
Anyway, in all seriousness, I cut the holes for a horizontal x-former like this:  
1. Remove the end bell (if it has one) and use it to mark the hole pattern for the bolts. The bell should also give a rough footprint for spacing. When you remove the bell, be careful to note if there are fiber spacers around the screw head- they are very important and must be reinstalled properly when you put the bell back on.  
2. Make a best guess on how large the square hole needs to be. Leave plenty of room for the wires to exit and that no windings around the base contact the chassis; however leave enough metal around the holes for support.  
3. Drill a 12" hole in each corner of the square hole, and then get a sabre saw with a metal cutting bit. Cut the square hole with the saw by joining the 12" holes near their outside edges.  
4. File the square hole smooth, drill the holes for the screws, and you're done.  
I hope this helps.
10/1/1998 12:17 PM

Rather than actually removing the end bell for a pattern, temporarily mount some of those threaded metal standoff posts made from hex bar stock onto the mounting bolt tips. This will raise the transformer body far enough above the chassis plane. Trace around the four pegs where they contact the chassis. Center-punch these "circles" and drill your 4 bolt holes. In lieu of tracing standoff footprints, you could just measure the bolt-to-bolt spacing and draw your rectangle directly. Even use a compass to transfer the measurements from point to point.  
I'm not criticizing your method, just trying to mention a few more points that might help others not so familiar with routine fabrication.  
Before drilling the bolt holes, connect the four dots with pencil lines. It should be a rectangle, sides parallel and right angles, so adjust accordingly. Move in about 3/16" and draw another rectangle, inside the first frame. Check the end bell for the place where the curvature diminishes, measure the length & width of those locations across the end bell's mounting surface. Adjust the previously drawn inner rectangle size, if you think it really needs to be larger, but it should already be fairly close.  
After drilling corner locating holes (large enough for the sabre saw blade to enter), cut the metal out carefully. Final cleanup of rough edges and any oversizing still required for end bell curvature clearance can be done with files.  
Some builders raise the transformer off the chassis slightly with flat washers to allow for another ventilation path, or if there isn't enough room for that much transformer to penetrate into the cassis due to other components.

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