"Cydrome Leader" wrote in message
...
In sci.electronics.repair William Sommerwerck
wrote:
"Cydrome Leader" wrote in message ...

That's pretty high tech for a product from the 1970s
to use a switching power supply.

My first color TV -- purchased in 1974 -- was a Sony KV-1920. It had a
switching supply.

that is pretty advanced.

I don't know which company was the first to make consumer products with
switching supplies -- but I wouldn't be surprised if it were Sony.

It could be.

the oldest thing in the junk pile with a switcher I have is an apple ][
computer.

Of course they forgot to add a cooling fan or ventilation slots which
Franklin Computer got right in their Ace series of clones.

I want to know more about this 1970s disco lighting system.



Discos were not confined to the 1970s. They still run now. In fact I was out
on one handling the lighting and visualizations for a friend, just this last
Saturday night gone ...

Anyways, I've fixed the bloody thing now, and I have to say that it had me
fooled. The problem turned out to be a knackered lamp socket. Looking closer
at the specs, it's actually 250 watts not 150 as I first thought, so even
with the forced air cooling it has, the lamp house runs pretty damned hot,
and the lamp socket with it. Basically, the ballast is not a very good
design. It doesn't run at all with no load on it, and as the lampholder was
effectively open circuit, it indeed didn't run, which was the first way that
it fooled me. The second way was that not only does it not run with no load,
it only runs properly with the full designed load. So when I had it out on
the bench, and just had a couple of 50 watt 12 v halogen lamps in series as
a test load, it ran, but only until the mains input voltage got to 160 v on
my variac. Once it went past that, the switching activity progressively
died, until it stopped altogether again.

I had a replacement ceramic holder to hand, as I fix a fair few of these
lighting fixtures, so I grafted it in, and reconnected the lamp wiring to
the ballast. This time, it kicked up and ran the lamp at full intensity
without issue, so that's one to remember if I come across another of this
particular fixture type.

Arfa