Need help replacing a power cord for an IBM Model 11 "C" Typewriter

[StudioAGT]

Hello all,

I'm new to this forum and came here because aside from having want to join for awhile, I'm quite stumped with connecting a modern power cord (US) to this machine.

Included is a picture of the back of the typewriter where a cord would go and a page from the respective Typewriter's service manual. It seems it is a 2-prong plug yet on the end of it is a 3-pin female end and that connects 2 wires to a condenser (capacitor) and one to the switch. I've never seen this sort of thing before. I'd like some advice please.

Thanks You in advance.

Sincerely,
Adrian

[StudioAGT]

It has come to my attention after searching the Repair section that the chassis inlet for this particular typewriter (which is from 1959) is similar to the PH-163, however, the pins in the inlet seem to align with each other where as in PH-163 connectors they're in a triangle arrangement (center ground pin being slightly above the left and right pins). Perhaps a proprietary connector like a lot of vintage equipment back then. I'd really like to change the inlet to a standard IEC C14 chassis inlet but I have no idea where to even begin. I remember usually the switch is on the hot side so perhaps the wired from inside that goes to the switch will be connected to the smaller (hot) side of a C14. As for the other 2 wires, not sure.

[StudioAGT]

Another observation:

Three pins but two prong plug. Looking again at the page from the service manual it looks like what's holding the condenser is a bracket, I wonder if that's a chassis ground, hence the 3rd pin? Would connecting that to the ground pin of a 3 prong plug make it safer? Hmm.

[perieanuo]

multimeter>check if middle pin goes with chassis (like close to 0 ohms resistance), and the other ones gives you some resistance between them.
be careful connecting them to mains, you have to be sure it's mains entry an not coming from some intermediar transformer in a box
you can open the thing and trace upto some internal transformer, in that age the transformers were marked with input/output voltages/currents.
post some pictures, someone will figure it out

[StudioAGT]

multimeter>check if middle pin goes with chassis (like close to 0 ohms resistance), and the other ones gives you some resistance between them.
be careful connecting them to mains, you have to be sure it's mains entry an not coming from some intermediar transformer in a box
you can open the thing and trace upto some internal transformer, in that age the transformers were marked with input/output voltages/currents.
post some pictures, someone will figure it out

Ah okay yeh I got a multimeter I'll check em out. Also I guess to really help everyone and myself I'll have to open up the typewriter (I'll have to anyway haha). Thank you for the suggestion.

[StudioAGT]

I happened upon the AMES Electric Typewriter Repair manual and it just so happened to contain a detailed schematic of the electronics (included).

And the connectors are intentionally proprietary, the middle pin is closer to the left side than the right and is indeed a ground. Oddly if I'm reading it right for some reason the neutral wire and ground are connected on one side of a 2 prong plug; why that is I can't say (but irrelevant I guess for converting to a C13/C14 connection). Perhaps now it'll be easier to replace with a C14 inlet, the middle pin would just be connected to the ground pin on a modern plug no?

As an aside I saw an article about "G-Girls" back in the day being shocked by this very type of typewriter due to plugging it in the wrong way (non-polarized). So if you weren't careful the chassis would be hot? In the article the problem went away when the repairman put the plug the other way. The chapter is G-Girls Shocked by Electric Typewriters from Safety Standards Volume XIV No. 1 1965. Yeah, I guess the two prong thing was because it was more convenient for the then current 2-prong only outlets rather than convert it to the safer three prong plug and outlet. They existed but not as common as they are now, some manufacturers included what we now call cheater plugs and people just left them on without connecting the ground wire.

[Ian.M]

Is there even enough space to fit a C14?  Offer up a C13 plug to the case opening to see if it can be done without extensive case surgery.   If not consider a C5/C6 ('cloverleaf') connector/inlet pair, as they are considerably smaller.    If that doesn't work out and you cant find anything else mains rated to fit, you could fit a permanent hard-wired line cord.

If you need to preserve it to original specs, you only have the evil option of trying to build a connector to fit.  The contacts aren't really a problem - a split hard brass tube of appropriate I.D. will make a reliable connection to those pins, however building a plug shell to fit with adequate contact and cord retention for safety  (preferably without 3D printing the shell in easily melted thermoplastic  ) is not so simple!

[StudioAGT]

Is there even enough space to fit a C14?  Offer up a C13 plug to the case opening to see if it can be done without extensive case surgery.   If not consider a C5/C6 ('cloverleaf') connector/inlet pair, as they are considerably smaller.    If that doesn't work out and you cant find anything else mains rated to fit, you could fit a permanent hard-wired line cord.

If you need to preserve it to original specs, you only have the evil option of trying to build a connector to fit.  The contacts aren't really a problem - a split hard brass tube of appropriate I.D. will make a reliable connection to those pins, however building a plug shell to fit with adequate contact and cord retention for safety  (preferably without 3D printing the shell in easily melted thermoplastic  ) is not so simple!

At most I was just thinking of desoldering the original chassis inlet, putting a replacement C14 inside and then see from there. I'd have to open up the typewriter first to truly see the situation even with a schematic (you never know if there was something not shown in the manual).

I also did think about just using a power cord with one end chopped off (3-wired) and connecting them to the pins on the existing inlet with soldered/crimped on tubes like you would find on Molex connectors but you are right that I'd have to find the appropriate ID connector to reliably slide and hold on to those pins lest we have a nasty loose connector situation. And you're right having a plug shell would make it safer but designing one with my abilities preclude 3D printing, I wish I knew how but if I really had to with my skills I'd probably make it out of wood!

[Ian.M]

*If* you have the skills and tools to make a good job of it, a fine grained durable high density hardwood would make a vastly superior plug body to any thermal 3D printable plastic, as it wont melt if one of the contacts becomes slightly loose and overheats, and if the wood species and grain direction are well chosen, it is likely to be significantly stronger.    Make the pin end and one side of the plug in one piece, drilled for the pin holes, then counter-bored from the back for the larger diameter for the contact sleeves, leaving enough at the pin end to retain them in their holes,  and drill and groove the side near the back so a cable tie can be used for the cord grip.  The rest of the plug body would be in the form of a close fitting partially hollowed out cover, with a ridge that partially obscures the contact holes so the contacts cant be pushed back as the plug is inserted, firmly screwed to  the first part.   Care should be taken to avoid a straight line path to any contact at the joint between the cover and the main part e.g. by putting a lip on the cover, so that conductive dirt buildup is unlikely to become a shock risk and to maximize the creepage distance.

Both parts should be made from kiln dried wood, and lacquered or preferably vacuum impregnated with epoxy or phenolic varnish to reduce the risk of moisture adsorption making the wood partially conductive, which could result in insulation breakdown, carbon tracking and possible fire.

I've made such connectors a couple of times for 12V applications, but am not sufficiently confident in my woodworking skills to attempt one for mains voltage use.

[perieanuo]

so it's mains, in your country should be 110V so no big deal to ...deal with.
beside design considerations (if you want to sell the machine), my advice is to eliminate that connector and secure firmly the cable after connecting the mains cable directly.
for securing, you have many cheaper options than changing the connector with lot of size matching issues...
having a removable mains connector in this case is not of big interest beside reselling purposes