4 Jul
2006
4 Jul
'06
9:31 a.m.
On 7/4/2006 at 3:53 AM der Mouse wrote:
I wrote about an old oscilloscope which was giving me
trouble. After
some poking and prodding, I managed to get things tweaked back into
operation. Then I was hacking on some software, pursuant to driving
the 'scope as an X-Y display off a soundcard output, when I became
aware of the 'scope making small popping noises.
When you described your beam-location problem, I was about to send an email
recommending that you check power-supply components, but changed my mind
when you seemed to have things straightened out. Apologies for the blank
message.
At any rate, the first order of business is to see if you've still got a
power transformer left. The easiest way is to simply remove all of the
tubes (I'm assuming that there are no solid-state recitifiers) and unplug
the CRT. Power it up and see if the transformer runs cool and silent. If
not, it's toast.
Old transformers are made with magnet wire, paper, cloth and varnish. Any
of this stuff can break down, resulting in a short. The popping you heard
was probably old varnish boiling out of the core.
If you discount the high-voltage anode supply for the CRT, an O-scope power
transformer is a pretty pedestrian affair. It's possible that if you can
locate a power transformer that has all the windings that you need but for
the CRT anode and filament supplies, you can use a separate transformer or
two to supply those voltages, if you have the room.
Before you plunk in a new transformer, however, you'll want to check all of
the electrolytics in the unit and look for possible short circuits.
Cheers,
Chuck