remember i posted the f48 ho tubes new in box?
funny how things happen but a friend has a garage we fix up stuff in.
the "attic" is a crude platform to store lightweight stuff in.i looked up at it and saw a approx 4'x2' plywood patch in it.
i joked that someone of my build must have gotten up there and came through.
no "thats an antique fixture that i am just keeping clean.cant buy bulbs for it but since it was put in in 61 when my grandfather built the place we are just preserving it".
since i cant get up there to see it i had him take the board off.
rdc sockets.hmmm.
wanna run me to the shop?i think i have these!
well it works fine with these!
he said it has huge starters bigger than a d battery.
it definatly is a preheater.lots of loud pinging and clicking on startup.
i thought ho were all rapid start.
h will lower it for pics and to see if the ballast temp is safe.
its sure a bright sucker!

Sounds like a cool adventure you had there....

There are Preheat HO ballasts, well not exactly but pretty close....

I have one for 1x110w HO on 240v 50Hz. It is labeled Quick Start but it is actually Capacitive Preheat with ordinary 2-pin electronic starter hidden inside the ballast enclosure (the starter can be swapped with a glow starter then it would be even more Preheat then it is now....)

The UK 100w and 125w 8ft T12s run on a mercury HID ballast which specs are 1.15A (at least when used with the mercury lamp), so i guess that would count as HO despite the tubes are not normally called HO. Starting is with  starter

this is a big heavy shoplight type fixture with the ballast and starters on top in a box.
120vac us spec.
so when were ho lamps with rdc base introduced?

You have GOT to post photos please!  The first HO (actually VHO) were the 90 and 100 watt T17s in the early 1940s.  I would love to see the ballasts and starters in that thing!  The 90/100 watt T17s have starters the size of a D battery but I have never seen any for anything smaller in the USA market...