The pulse-dial telephone and its associated mechanical exchange represents the pinnacle of late-19th and early-20th century electromechanical technology, but its vestiges have disappeared from view with astonishing rapidity. [Matthew Harrold] is a telecoms enthusiast who’s been kind enough to share with us the teardown and refurbishment of that most signature of pulse-dial components, a telephone dial. In this case it’s on a rather unusual instrument, a British GPO outdoor phone that would have been seen in all kinds of industrial and safety installations back in the day and can probably still be found in the wild today if you know where to look.
The teardown soon identifies a dial that runs very slowly and is sorely in need of a clean. There follows a detailed part-by-part dismantling of the dial mechanism, followed by a careful clean, polish, and reassembly. He notes that a previous owner had used grease to lubricate it, probably the reason for its slow operation.
The result is a smoothly running dial and a refurbished phone that would probably last another half-century or more before needing more maintenance. It’s enough to make others who’ve experimented with pulse dial phones very envious.
8 thoughts on “A Dodgy Dial Gets A Teardown And Some Oil”
My old phone’s dial became “dodgy” being stored in the garage (humidity?),
Does anyone have a source for the “telephone oil” like he used?
It looks like “GPO Rotary Dial Refined Mineral Lubricating Oil” which a quick search brings up this as a source: https://www.britphone.net/gpo-rotary-dial-refined-mineral-lubricating-oil-10ml-342-p.asp.
Old NY Telephone tech, we used to carry spare dials and just swap them out on site and send the defective ones back to Western Electric in Syracuse for refurbishing. When I moved to the Teletype group, we would swap out the dials on some of the old TTYs and take them back to the shop and refurbish them ourselves. We had a guy who never could get the hang of taking the spring out of the governor, so we nicknamed him “Pinnggg.” The biggest problem with the dials, early on, was cigarette smoke, that stuff would gum eveything up.
Nice read. I’ve been lucky with my rotary dial phones so far. But sooner or later one will turn up that needs more than a light cleaning.
Haha – brilliant!
I have a Northern Telecom rotary dial that has been needing this exact TLC, so this is getting bookmarked for when it gets taken apart for cleaning :)
This retro tech stuff is great. Keep it coming!
My understanding is that pulse dialing only has gone away as Verizon enabled DSL.
Back in High School we learned how to dial out from locked phones by clicking the receiver button to pulse dial. Then there was trying to dial as fast as possible, pushing the dial back as fast as it will go, to try to win tickets from radio stations.
I remember the same thing here in Tennessee. Last time I tried a phone with a pulse dial switch it still worked.
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