Author Topic: Converting magneto/local battery to common battery  (Read 275 times)

Offline scottfannin

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Converting magneto/local battery to common battery
« on: May 19, 2020, 02:03:23 AM »
Continuing this in a separate thread.  Article http://www.classicrotaryphones.com/forum/index.php?topic=23802.msg237683#msg237683 was about inductors but it evolved into how to make a magneto/local battery device into a common battery one that can connect to a modern phone line.  For wooden wall phones and for early wooden subsets.  You can catch up on page 2 or so of that.  Where last we left it, we were making circuits for changing a wooden wall phone to work on a common battery system.  I have attached the most recent incarnation of a diagram for this as a carry over from the original diverged topic.  I'm pretty good with Visio so we can pretty readily convert what people share into documented versions and then send them back out, which is what we were doing. 

Being forced to hide, my relatively new telephone skills are advancing more quickly before.  I live in New Jersey just across from the New York border.  I only leave my house every 3 weeks to exercise the car and buy food because people I actually know are ill and a few people's relatives actually died.  Fun fact, my town has a large monument to the 1918-1919 flu epidemic, which was really bad here too.  So I have some time to study these things now.  And a kid to amuse, he hasn't left the house in something like 7 or 8 weeks now.  He's become able to tell a Stromberg-Carlson from a Western Electric just by looking and can guess the age of a WE 317 just by looking and he assembled a WE 500 from scratch using just the wiring diagram from TCI, not bad for 11 but when you're kind of in a nice cage for days on end you can learn stuff like that. 

But anyway, today we worked on condensers.  You need them for the modern phone network.  0.47uF for the ringer.  Give or take 2uF for voice if you can work it in.  But if you're lucky sometimes you find a single huge capacitor in the wooden phone.  It can be anything from 1uF to 5uF, often 2uF.  Even if it works perfectly, it will only be one.  Plus my experiments to see what happens if the ringer capacitor is not 0.47uF have shown a limited tolerance for that.  I see people solder wires onto a mylar capacitor and kind of suspend it in the air with no insulation.  It looks awful.  Bad enough you can't "restore" something that was rarely even there, but does it have to look too low-budget for old Doctor Who?  So we get to thinking, what do we have around?  We had stripped and re-stained two badly destroyed wall phones.  So we have some dark walnut Minwax left, from before the local hardware store closed down.  We have water-based polyurethane.  We have big and small size 0.47uF and 2.0uF film capacitors.  We have heat shrink tubing.  Solder.  One of those paddle-shaped drill bits for boring big holes in wood.  Glue.  I found some unexplained wood junk in the crawlspace, probably came with the house but it wasn't pine, there was some grain to it and no knots.  We have a miter saw machine and a drill press.  So...let's make "Amish Condensers"!

1) Chop the wood into various experimental shapes, sometimes making thin slices for potential covers.
2) Hollow them out with overlapping paddle shaped drill bit and drill press.
3) Sand lightly to remove splinters and rough edges.
4) Stain.
5) Coat 2 or 3 times with polyurethane, making sure last one is "matte" for that pseudo-patina look.
6) Select appropriate capacitors (shaped and sized for the block ideally).
7) Place solder blobs on the leads near the component itself.
8) Force small heat shrink tubing over most of the leads, leaving maybe 1/3 inch at end.
9) Shrink it, now the blobs act like holders even though the leads are usually too thin for the shrink tubing.
10) Drill 1/8" holes as appropriate in the wooden blocks.
11) Force the component leads through the holes.
12) If appropriate, put a lid on.  For some, just put the open side against the wall of the phone to protect it.
13) Usually, you can't drill through some side of it because the point of the paddle bit would go through.
14) Drill across that to make a hole for a wood screw or two to fasten it in the phone.
15) Bend the leads over a little so they are inclined to stay.
16) Stuff cardboard into any space left inside the hollowed block.
17) Hook the capacitor leads and some "condenser leads" together and solder.
18) Optionally shrink tube your connections on the outside of the condenser.
19) It's ready to go and looks pretty convincing.
20) I've attached a picture with some of my experiments.

So who knows how to make yourself an inductor?

Offline dsk

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Re: Converting magneto/local battery to common battery
« Reply #1 on: May 19, 2020, 05:27:06 AM »
Great ideas, and of course you may pretty often use whatever you have of old phone parts.

The induction coil where you only use one winding may be replied of approx any transformer or relay with a high number of turns and a winding with a resistance of 15-100 ohms.

It will of-course often be better if you have a coil from a CB telephone and use it with the circuit equal, or close to equal with the original circuit. 

Regarding ringers, the most of the old ringers (non party-line) will do the job, at least if the magnet is still having a little of its magnetism.  If the total resistance of the coils are less than 600 ohms (Common on older German phones with only 600) you are on the edge of what who is easy to use.  Most ringers works well in series with a 0.47 uF capacitor, but some of the older ones may require a higher value.  It look like weak permanent magnets pretty often are helped by the use of the ringer, so weak ringer may be stronger after some use. 

When it comes to receivers with a flat iron membrane the distance from the magnets could be adjusted by putting in or remove thin rings of paper put between the membrane and the receiver element.  I'm looking forward to see how this project will turn out, it is almost as building a new old phone  :)

I have to admit that when I got a 1920 ish European S.E. telephone with no transmitter and no receiver did I put in elements from a WE 500 that did get in and just packed up with some cotton. That phone worked so well that I was asked if used a modern phone  8) and that's not common for me.

dsk
« Last Edit: May 19, 2020, 05:34:44 AM by dsk »

Offline scottfannin

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Re: Converting magneto/local battery to common battery
« Reply #2 on: May 21, 2020, 12:46:47 AM »
Today's work on the Kellogg restoration--to be the first complete wooden wall phone I make.  We got a wood wall phone cheaply, American Electric, from Goodwill several months ago, when you could still do that.  It was rusty and full of mud--literally.  I don't know the history of it.  The wood was weirdly solid, but the induction coil was mush.  The bell coils looked like disaster victims.  No winding covers, caked with mud, rusty metal parts.  But what the hell.  I blasted them with WD-40, then de-greased, rinsed, and generally made my wife's laundry sink look like the shower scene in Psycho.  Then quickly hair-dryed.  Amazingly they worked, excitedly and strongly ringing the badly bent clapper.  So in for naval jelly.  Then muslin wrap to make what I think looks nice if not original.  I soldered the hair-like wire between them to patch it after it snapped during muslin wrapping with 0.015 thickness solder.  I glued the wrapped wire to the edges of the cylinders so it would stop unraveling.  Then using two helping hands, I soldered cloth-covered tinsel wire to the fine wires and shrink-tubed it.  Crimped ends on, one with tracers so it looks mysterious to a viewer.  Turned them carefully during re installation in the bracket so that the fine wire between them was held tight and thus not touching the bracket, so I didn't have to put a lame looking muslin square to insulate it.  Pinned the shrink-wrap in the mechanism as I tightened it, so the exposed few mm of the winding wires wouldn't touch the bracket either.  Placed it in the tester with phone line and 0.47 uF ringer capacitor, and it's clean and rings like a puppy wagging its tail.  It's amazing what you can do when you're hiding out from the plague in your basement all day.  Picture attached.

Offline dsk

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Re: Converting magneto/local battery to common battery
« Reply #3 on: May 21, 2020, 03:13:04 AM »
Looks great!
dsk

Offline RB

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Re: Converting magneto/local battery to common battery
« Reply #4 on: May 21, 2020, 08:08:11 AM »
Nice work!
Tiny wires are Sooo much fun to work with! ;)

Offline scottfannin

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Re: Converting magneto/local battery to common battery
« Reply #5 on: Yesterday at 11:38:42 PM »
So we're almost done.  It works.  We've got a sort of punch list we're working through, like we need to add the door fastener, that cage nut and screw thing.  We need to get acorn nuts to fit the bells.  An easy thing but we will attach the shelf last because obviously that is subject to scratching while working on the rest.  Based on "feedback" (well, to myself and my assistant) we have designed a new Amish condenser.  Soldering tinsel upside-down while it was fastened into the box with bent leads for terminals was a bit tedious and presumably error-prone even though in this case it worked.  I separated stranded 22 gauge wire as recommended in a post somewhere here and then tied the tinsel together with a few knots under a magnifying glass, tinned it, and then soldered it like it was solid wire.  Next time, screw terminals and crimp connectors.  I've attached the new condenser design.  "CEI" is the pretend company my son and his friends operate when playing "technology startup".  No cops and robbers anymore.  "Ghost" is what they call the wooden models of the pretend phone offerings, of course (never mind that it's the only one so far).  Mk. 2 because it's the second iteration.  My point is none of the name info means anything but us goofing around.  The shell will be made out of scrap wood hollowed, drilled, and then once known to be a surviving piece (I shatter about half right now, due to extremely primitive tools), stained and coated with my quick antiquing.  It will get 1 coat gloss oil-based polyurethane and then 2 coats of matte water-based polyurethane--instant old.  Closing the back?  No problem, if you screw it in so that the back faces a wall, there isn't a need for a back and no line where you glued it.