[Test-Equipment] a 'dumb' scope question.

[KA4INM]

   On 05/04/14 15:17, Ron Bussiere via Test-Equipment wrote:

> They power up but I cannot find the trace on either. "beam finder' tries to work. In the background of the CRT, you can 'see' some stray illumination flashing when you vary the timebase. Using the internal cal also has no effect. It's like the trace is off the screen and no fiddling with any channel / position knob will bring the trace onto the CRT.

> I suspect the HVPS, and looked to see how difficult it would be to get to the caps. I think it would be a better move to pitch the scopes into the trash.
> The entire scope appears to be built around the HVPS.........WTH???

> It's just strange that 2 Kenwoods would have the same problem......

> Any ideas?????

   With no inputs into the scope under test:
   First, if you can take one of those HP or Tektronix scopes with two 
low capacity probes (in the "chopped" or "alternate" mode with one input 
inverted - zeroed) and look at the two horizontal deflection plate 
connections and adjust the horizontal centering until the two plates are 
at as close the same Voltage as possible, you should be able to get the 
two traces to cross.

   Next do the same with the vertical plates and the vertical centering 
control.

   If the above is not possible on either set of plates, there is your 
problem.  If the deflection plate connections come out of the neck of 
the gun structure as pins as they do with Tektronix tubes the above is easy.

   Many manufacturers have used a one watt resistor where HP or 
Tektronix would have used a two watt resistor, this is one thing that 
makes such common failures, common.
   (Hi fellow Ron!)
-- 
   Ron  KA4INM - Youvan's corollary:
                 Every action results in unwanted side effects.