XPost: alt.home.repair, uk.d-i-y
From: roger@hayter.org
Max Demian wrote:
> On 03/03/2019 18:59, Mark Lloyd wrote:
> > On 3/2/19 1:20 PM, Art Todesco wrote:
> >
> > [snip]
> >
> >> Here's the way it is. There are 2 full wave rectifiers. The DC
> >> outputs are connected together; + of each and - of each. These feed
> >> the converter which is the standard chip, pulsing a transformer. The
> >> output of this is 1/2 wave rectified, filtered and goes to the string
> >> of LEDs. Now back to the 2 full wave rectifiers (FWR). One input to
> >> the 1st FWR comes from a pin on one end of the tube and the other
> >> input to the 1st FWR comes a pin on the other end. The 2nd FWR is
> >> wired the same way, except it uses the unused pins on the ends of the
> >> tube. For some reason there is a 5 ohm resistor in 3 of the 4 inputs
> >> to the FWRs. The 4th is direct connected. But if you trace is out,
> >> you can supply 120 VAC to any 2 pins and it works. You can even power
> >> from one end and short the pins on the other end and it still works.
> >> Clever!
> >
> > And I seem to remember some that work on any supply voltage from 120V to
> > 277V.
>
> Did anyone need to run a TV on DC, or was it just to save having a heavy
> mains transformer?
I don't know when the last public DC mains supply was replaced, but I
tend to think that AC/DC TVs were actually designed to work on DC mains
up to the early 1950s at least.
>
> There were certainly AC/DC *radios* that would cope with 120V to 250V or
> so. Needed a whopping great dropper resistor when working on the higher
> voltages. I used to have such a (portable valve) radio which would work
> on battery as well. The dropper was originally in the mains lead but had
> been replaced with a component in the case.
--
Roger Hayter
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
