01-27-2015, 07:37 PM
Been procrastinating digging into the power switch on my 41-280 for over a year while prowling hamfests for a proper looking old switch.
Got the original working over a year ago with some DeOxit and poking in one of the wires that had been whacked short back and was loose. Worked, but barely.
Seemed the best idea was to keep the bits of brass rivet out of the bottom so did a tape off before starting with he Dremmel. A shop vac got things cleaned up before removing the tape and paper.
[Image: http://i1356.photobucket.com/albums/q734...f9b1cf.jpg]
The switch slid off the rivets fine and interior looked OK so figure it was hard grease for the failure that caused a toggle switch to appear in the side of the case.
Referring to the pictures in The Notebook http://www.philcoradio.com/notebook/41226.htm it appears the wires were soldered to the contacts in some of the switches. From the look of mine only a little arc solder melt occurred. Maybe an original defect. The wire still held in firmly was held by pressure on the insulation. The short wire end was mostly gone but had not damaged the contact finger.
[Image: http://i1356.photobucket.com/albums/q734...cf2b_1.jpg]
The remaining wire is just slid behind contact - not soldered
[Image: http://i1356.photobucket.com/albums/q734...a8f8_1.jpg]
Replacement wires were soldered to the contacts like the picture in repair notebook. This is the original switch.
The idea of using a screws to mount the switch made a lot of sense. The outboard rivet appeared to have the flange stuck in the assembly, but some wiggling and mashing with needle nose pliers if finally dropped out. The inboard rivet fell out fine.
Rivet OD was 0.093" The push button frame holes would pass a #42 bit .093", but not a # 41 .096". My chart shows a 4-40 tap drill as #43 .089 for 70.8% and a 4-48 as #42 for 68.4%. The clearance hole spec is a #33 but a 32 .111" is enough and leaves more original body so that was used to enlarge the holes in the original switch.
Checking the price on 4-48 machine screws made 4-40 screws (that I have lots of) with a #42 hole @ 57% look OK.
The outboard mounting hole has a slight over lap of the back of the push button assembly end plate a bit under the surface. Take care not to jam your tap & SNAP! Got about 2 turns on a taper tap, another 1 or 2 with a plug tap and finished with a bottom tap. Tapping here is an exercise if slow and cautious.
Screw length is also critical in both holes. The inboard will stop the operator if it is too long or has a standard size head. Get a small size head or use a grinder. The outboard has interference in my switch stack, maybe not yours.
[Image: http://i1356.photobucket.com/albums/q734...9e05_1.jpg]Note the small screw head on the inboard mounting screw. It has to be flush with the edge of the case.
The bracket is thin so use a gentle torque on the screwdriver.
I like fuses so added an inline 2A on one switch wire to the transformer. In picture above.
Finish up Knobs and push buttons
The push buttons were sliding on hard. I tried a bit of silicon grease on the metal and added a tad inside the new push buttons with a dental pick. Did the same on the knobs. Wonder what others have tried.
Got the original working over a year ago with some DeOxit and poking in one of the wires that had been whacked short back and was loose. Worked, but barely.
Seemed the best idea was to keep the bits of brass rivet out of the bottom so did a tape off before starting with he Dremmel. A shop vac got things cleaned up before removing the tape and paper.
[Image: http://i1356.photobucket.com/albums/q734...f9b1cf.jpg]
The switch slid off the rivets fine and interior looked OK so figure it was hard grease for the failure that caused a toggle switch to appear in the side of the case.
Referring to the pictures in The Notebook http://www.philcoradio.com/notebook/41226.htm it appears the wires were soldered to the contacts in some of the switches. From the look of mine only a little arc solder melt occurred. Maybe an original defect. The wire still held in firmly was held by pressure on the insulation. The short wire end was mostly gone but had not damaged the contact finger.
[Image: http://i1356.photobucket.com/albums/q734...cf2b_1.jpg]
The remaining wire is just slid behind contact - not soldered
[Image: http://i1356.photobucket.com/albums/q734...a8f8_1.jpg]
Replacement wires were soldered to the contacts like the picture in repair notebook. This is the original switch.
The idea of using a screws to mount the switch made a lot of sense. The outboard rivet appeared to have the flange stuck in the assembly, but some wiggling and mashing with needle nose pliers if finally dropped out. The inboard rivet fell out fine.
Rivet OD was 0.093" The push button frame holes would pass a #42 bit .093", but not a # 41 .096". My chart shows a 4-40 tap drill as #43 .089 for 70.8% and a 4-48 as #42 for 68.4%. The clearance hole spec is a #33 but a 32 .111" is enough and leaves more original body so that was used to enlarge the holes in the original switch.
Checking the price on 4-48 machine screws made 4-40 screws (that I have lots of) with a #42 hole @ 57% look OK.
The outboard mounting hole has a slight over lap of the back of the push button assembly end plate a bit under the surface. Take care not to jam your tap & SNAP! Got about 2 turns on a taper tap, another 1 or 2 with a plug tap and finished with a bottom tap. Tapping here is an exercise if slow and cautious.
Screw length is also critical in both holes. The inboard will stop the operator if it is too long or has a standard size head. Get a small size head or use a grinder. The outboard has interference in my switch stack, maybe not yours.
[Image: http://i1356.photobucket.com/albums/q734...9e05_1.jpg]Note the small screw head on the inboard mounting screw. It has to be flush with the edge of the case.
The bracket is thin so use a gentle torque on the screwdriver.
I like fuses so added an inline 2A on one switch wire to the transformer. In picture above.
Finish up Knobs and push buttons
The push buttons were sliding on hard. I tried a bit of silicon grease on the metal and added a tad inside the new push buttons with a dental pick. Did the same on the knobs. Wonder what others have tried.
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