I restore antique radios and recently picked up a very unusual GE window sign with a Mazda 15W blue fluorescent bulb inside.  To start the bulb, you have to turn the switch on then forward for 2-3 seconds and let go to make the bulb start.  I have never seen this and wondered how common this is/was?  Also, it had two capacitors, one on each side of the AC line.  As they were not marked, I replaced them with .01@630v mylar caps. 

No ideas?

The Push/Hold/Release starting method was common.  The blue Mazda lamp, that's pretty rare and old! Be careful, it has zinc beryllium phosphors, and if broken those are VERY toxic, as in causing gangrene in open wounds kind of toxic.  Very neat fixture, though!

Thank you for the note.  I have a couple of other single bulb signs from the same period but none with the push to start switch.  They just go on when plugged in.  Do you know why it has capacitors on the AC line.  Did this have something to do with the special switch?

Regards,
Donald

My guess is if it was across any part of the switch is to prevent arcing of the contacts and prolong the switch life. In my 1949 circline desk lamp it had a .006uf cap across the line and neutral, my guess is noise suppression on the line or again some sort of starting arc suppressor. If the other signs you speak of come on when plugged in, and they're late 30s, you could have done very rare magnetic or thermal aux ballasts. Please post pix if possible of the ballasts.
Welcome to the club bulb buddy btw.

The condensers across line and neutral will be for noise suppressor probably better than normal suppressor as its in a radio shop the last thing you need is noise to spoil reception of the radios your trying to sell. Also would probably be fairly effective in band 1 tv to stop noise bars on nearby tvs

Thanks again.  I am surprised it works and the Mazda 15W tube is good.  Really pretty blue color.  I bought two replacements as I understand they don't make blue T8's anymore.

Donald

Buying replacement tubes is a good move. Interlectric still has the F15T8/B listed on their site, and I found this site where you can buy them individually, but it probably won't be long before you won't even be able to buy those tubes anymore.

I'll share what I found.  This place was a lot less expensive and the bulbs arrived well wrapped.
https://atrlighting.com/

Donald