Michael Black wrote:
On Fri, 19 Apr 2013, Noel Keith wrote:
So, I recently got a Tektronics 545B oscilloscope. It's been sitting
in a basement for god knows how long, and I thought it would be cool to
see if it worked. well, it doesn't. It's missing it's fuse and fusecap,
and it's power cable. I had read in a couple of places that the fuse only
affected the high voltage stuff, like the CRT. I might be totally
wrong about this, which is why I'm asking you guys 
Well, with that in
mind, I found a newer power cable that seemed to fit the bill, so I tried
using that. Nothing. I then tried using a voltage regulator. Still
nothing. Now, I'm not sure if it's because of the mysterious missing
fuse, or if something else has gone bad inside, or if it was the
power cable (which I doubt). My next guess was that it was the missing
fuse. Holy crap does this thing have a strange fuse. I've looked all over
for something with a similar rating and size, but with no luck. I'm not
as worried about the fusecap.
Of course the fuse takes care of the whole thing, it's in the primary
to the power transformer. F601, it's a 6amp fast-blo 3AG fuse for
120vac operation (3ampts if running off 240v). It's a standard glass
fuse, you should be able to get them anywhere. It goes into the
fusecap, then you screw (or is it turn?) the fusecap into the holder
at the back of the scope. I don't know where the fusecaps can be
found these days, I suddenly find I need one and can't find any among
all the junk.
Nothing will happen unless that fuse is in place, and that includes
the fusecap.
There's also a thermal cutout fuese in series to the primary of the
power transformer, but that isnt' even a factor until you get the
proper fuse in there witha fusecap.
I got one 20 years ago, though havent' had it on in about 10 years. It was
working fine when I got it, but I since someobody found it at a
hospital as it was about to be tossed out, I suspect it was still in
operation. It worked for a while, then the trace got bent. It's a
multiple section power supply I wasn't sure which section was the
problem, I found it by taking the probe and touching each of the
sections across their filter capacitor, until the waveform got worse.
Changed that filter capacitor, and all was fine. It is incredibly
bulky, which is why I moved it to the basement and thus it's a lot
less useful, so it just sits there.
Michael
I searched for a couple weeks online, but I
eventually came to the conclusion that the thing would probably never
work. Today though, I thought I'd give it a go again. Back of the
oscilloscope: http://i.imgur.com/uM64sfX.jpg I opened it up to find
TONS of gunk and dusk blanketing it's insides. I also found a pdf of its
manual (which has slightly more info about the missing fuse). Now I
think I got in over my head, because I'm too scared to touch
anything. Before I go fiddling with 50 year old electrical components, I
want
to know if it works or not, what I can do to fix the fuse situation
(even if only temporarily), and if I should check for anything else.
So, can anyone help me? I'd REALLY like to get this guy working
again, but I need some help (obviously, hehe...)
I think that you really are over your head with this old scope if you can't
deduce that a missing fuse is probably the reason that it doesn't light up.
This scope isn't for the faint of heart to work on. Since it's been idle
for who knows how long, then it's almost ceretain that most, if not all, of
the power supply filter capacitors need to be replaced, along with many more
electrolytics in other circuits.
Most of the power supply sources in it are regulated, and sometines even an
experienced technician can find them hard to get right. Ripple and noise on
the voltage sources are critical to proper operation of every circuit in the
scope.
As for the dirt, I understand that the Tektronix service dept used to
actually wash scopes that had been traded in for newer better scopes down
with detergent and a low pressure garden hose. Then the scopes were air
dried for several days (in a warm, dry place). Then, repair and calibration
were performed.
The scope can almost certainly be restored to working condition, but that
usually takes someone with proper knowledge, experience and test equipment.
You need another scope and a good DMM just to get the power supplies running
properly,
--
Dave M