Lightbulbs as a "constant current" source is electrical engineering 101. Analog arts have been lost in recent years.
Inside the vintage Xerox Alto's display, a tiny lightbulb keeps it working
51–54 of 54 posts
Re: Inside the vintage Xerox Alto's display, a tiny lightbulb keeps it working
#52Earlier quoted context omitted.
> My old Dodge instruments need 5 volts, so there's a mechanical device to convert 12V to 5V. It involves heating a bimetalic strip that opens and closes a circuit quickly, i.e. buzzing, which produces 5V. Are you sure that this is not a https://en.wikipedia.org/wiki/Vibrator_(electronic) that would be powered by a solenoid and not just a bimetallic strip?
I think you're right.
No.
You were actually initially right, I searched for that actual part and it is indeed a bimetallic strip along with a heater (that turns off when the strip moves away from a contact) and not a device with a solenoid/relay.
Apparently whatever it supplies is tolerant of that sort of interruptions in its power source -- I imagine that it would operate on a quite lower frequency than a "vibrator"-type power supply where magnetic force moves the contacts (and elasticity returns them).
Re: Inside the vintage Xerox Alto's display, a tiny lightbulb keeps it working
#53Earlier quoted context omitted.
I think you're right.
No. You were actually initially right, I searched for that actual part and it is indeed a bimetallic strip along with a heater (that turns off when the strip moves away from a contact) and not a device with a solenoid/relay. Apparently whatever it supplies is tolerant of that sort of interruptions in its power source -- I imagine that it would operate on a quite lower frequency than a "vibrator"-type power supply whe…
I read about this probably 10 years ago, my memory was clearly a bit faulty on it. I didn't want to take the device on my Dodge apart just to verify it :-).
The thing is, the instruments require the noisy 5V.
You can buy kits with an electronic 5V source, and also to replace the old guts of the instruments with modern ones. That retains the original look, with modern accuracy and performance.
Re: Inside the vintage Xerox Alto's display, a tiny lightbulb keeps it working
#54Earlier quoted context omitted.
Hmm... If regular CRT televisions behave the same way, that means at some point in time it would have been possible to create a "jamming signal" that transmitted a signal with the wrong refresh rate and blew up all the TVs in the area.
Regular CRT televisions weren't multisync - at best they'd be able to deal with both 50Hz and 60Hz inputs, but they wouldn't attempt to sync to anything else.
Multisync means the CRT will succeed at syncing to multiple specified frequencies.
There is nothing stopping non-multisync monitors (including TVs) from trying to sync to an out of range signal and depending on the design they might damage themselves trying.