Wanna smash a CRT? Let Australia Post do it. - Page 2

On Sun, 10 Sep 2006 19:06:15 +1000, "Phil Allison"



   You're thinking of someone else. This is an old workmate from back
when I was in Telecom, who lives in southern NSW now.




   Yeh, I agree. It's not clear exactly where the glass initially
broke, because 'the atmosphere has done the work' and blown quite a
lot of the fragments inside the envelope. It looks like it happened
under two of the gun support springs. There's a full size closeup
photo at http://members.ozemail.com.au/~bobpar/DSC01949.JPG
   Maybe the envelope contacted the inside of the shield, or just
failed by itself as you said, when it got mechanically jolted. The
glass is pretty thin.
   There's no sign at all that the CRO's been dropped etc before my
mate packed it up and posted it. No pushed-up feet, dents or anything.





   Pricey little devils, aren't they? :-)




   I'm making enquiries to see if they have any spares, but I don't
think they will.


Cheers
Bob

**Jeez, I wish you'd asked. I have a brand new one (tube), boxed (in
original packaging) and ready to go. GE-MOV branded. I have an 821 'scope
too. It's not working right now, but I'll get around to sorting it out one
day. Nice thing, being real dual beam (not dual trace) and all. Big coil of
coax for a delay line inside. I've got a spare delayed sweep plug in and a
diff amp somewhere too. I seem to recall that the delayed sweep is buggered
though.

"Trevor Wilson"







**  Wrong CRO   -  TW.

 The CRT in the BWD 821 is a " 140CGB31"  by Matsushita.

 8 x 10 internal graticule,  mesh PDA type.

 My BWD 821 was bought new in August 1985.

 It is 50 MHz, dual trace.

 I also have the similar BWD 824  as a spare.





......   Phil

**Mea culpa. I was thinking BWD 521.



**The 521 had no internal cratcule, but was, of course, a PDA tube.



**The 521 is a 30MHz device.



**I stopped using my BWD when I bought my first Tektronix. The BWD was nice,
because it can be serviced economically.

On Mon, 11 Sep 2006 14:48:01 +1000, "Trevor Wilson"



   I've got a 521 with the dual beam CRT. The poor old thing's got
drifting components right through it and the rotary switches keep
developing tin whiskers.
    CRT has always had internal leakage between the guns, so changing
the brightness on one affects the other (yes, I've measured the
leakage right at the CRT's pins).

  If anyone wants this CRO with differential vertical amps, I think
I'd give it away...


Bob

Location ?

On Mon, 11 Sep 2006 18:19:22 +1000, atec 77 <""atec 77 \"@
hotmail.com"> wrote:


Southern Sydney

I have a 50Mhz module for mine.



If you are offering the 521 Parts and Tube I will not turn them down .....
;-)

Regards
Richard Freeman

On Sun, 10 Sep 2006 19:06:15 +1000, "Phil Allison"


   After I removed the external rubber sleeve, some of the aquadagged
glass fell into the tube and now I can see that at least one of the
gun support "rails" was snapped by the shock. The deflection plates
are rattling around, shorting to each other and possibly the aquadag,
and it's lucky it didn't take out some of the circuitry when I powered
it up.
   I've added a close-up photo to
http://members.ozemail.com.au/~bobpar/Q1803/austpost.htm
  



   DSE actually sold me a replacement at a very reasonable price. The
first bit of good news in all of this.

   The only problem with the new tube is that the intensity pot needs
to be about 90% of full clockwise before I see the trace and it's not
real bright at full clockwise. Is your Q1803 like that? I got the
schematics for it, and there's no sub-intensity trimpot, only a
trimpot for setting the G2 voltage which I presume's the astig
adjustment?


Cheers
Bob

"Bob Parker"

 After I removed the external rubber sleeve, some of the aquadagged
glass fell into the tube and now I can see that at least one of the
gun support "rails" was snapped by the shock. The deflection plates
are rattling around, shorting to each other and possibly the aquadag,
and it's lucky it didn't take out some of the circuitry when I powered
it up.
  I've added a close-up photo to
http://members.ozemail.com.au/~bobpar/Q1803/austpost.htm


**  Remember  -  once the glass fractures,  there is 7 kg of force per
square inch ( due to atmospheric pressure ) behind the chunks that implode.
Do a bit of damage, they would.





** Would they sell me a spare for the same ??

    Looks like those tubes are tad fragile  ;-)





** No -  the trace is visible from the 8 o'clock setting onwards.

 About 1 or 2 o'clock is my normal setting in subdued room light  =  about
50 to 10 lux incident on the screen.






**  Yep.




.......  Phil

On Thu, 14 Sep 2006 00:22:08 +1000, "Phil Allison"



   You're not wrong. Whatever happened, the forward part of the gun
assembly's a real mess now.





   I don't see why not. By 'very reasonable' I mean a bit over $50.
Cheaper than a new CRO, anyway.





   The glass is fairly thin, except on the flat face of course.





   That's what I'd expect. Looks like I might need to adjust the value
of the intensity limiting resistor in series with the intensity
pot/rheostat. Unless this little incident's damaged something else...





   Thanks for the info. It always helps to compare a repaired one
against one which has been OK from the start. :-)


Bob

On Thu, 14 Sep 2006 00:22:08 +1000, "Phil Allison"


   I've just torn the CRO apart and checked everything related to the
G1 voltage adjustment.
   My schematic shows R115 as 33K but the actual resistor's 75K. Seems
likely that they select them on test.
   Now if only my component collection was still here, not where I'm
working...

Bob

"Bob Parker"




 **  You bet.

 Dem tubes are exactly as " dim as they sim "  .....





.......  Phil