[Central-Electronics] CE-100V Scope

[w7fe]

Hi Gordon,

Normal operation of the CE 100-V's front panel oscilloscope display is as 
follows:

The 'scope is inoperative until the transmitter is enabled to produce an RF 
output signal.  Upon generation of a  continuous CW signal a vertical trace 
appears, filling about 3/4 of the 'scope area and roughly on the tube's 
vertical centerline.  When RF modulation (of any type) is generated, a 
trapezoid (or triangle) -shaped pattern appears, roughly centered in the 
'scope display area, and expanding and contracting in size concurrent with 
the  modulation.

It would appear that the scaling resistors for the 'scope circuit in your 
100V are out of tolerance such that the pattern is filling too much of the 
'scope display area. The "garble" you see may well be the trace which 
appears inside the trapezoid pattern.  You may verify this hypothesis by 
reducing the 100V's power output control until the trapezoid pattern 
appears.  It may not be in the center, but at least some recognizable 
portion of a trapezoid/triangle pattern should become visible.

Most likely the necessary repair will be to check and replace any 
out-of-tolerance resistors in the 'scope circuit to get a properly scaled 
and centered  pattern to appear.  I believe that some of these will be the 
2.2 Meg resistors that I found necessary to replace in my 100V a few years 
ago in order to center up the displayed trapezoid/triangle pattern on the 
'scope.

If you're interested, the way this works is that an RF signal sample from 
the PA is applied to the 'scope tube's vertical plates when transmitting. 
Simultaneously, an RF sample from the driver stage is demodulated (thus 
becoming an AF signal when in the audio modulated modes) and applied to the 
horizontal plates (there is no time-based "sweep" circuit as found in a 
bench 'scope).  In the carrier-suppressed modes, the pattern produced will 
be a very nearly perfect equilateral triangle.  If carrier is added, the 
short end of the pattern will be truncated (thus producing a trapezoid) 
until 100% modulation is achieved whereupon a triangle is then displayed. 
Overmodulation will add a 'tail' to the left point of the triangle. Issues 
such as under-loading, under/over-biasing, splatter, spurs, and others may 
be observed using this display scheme but are unlikely to appear on the 
100-V (there are no front panel 'adjustments' available.to correct them 
anyway).  Images of  the patterns produced by these anomalies can be found 
in any monitor scope manual (such as the CE MM-2, Heath HO-10, etc.), 
available via a quick Google search.

I hope that the preceding notes will help you identify and correct your 
100-V's front panel oscilloscope display problem.

73 de Stu, W7FE
Henderson, NV
100V S/N  E73



----- Original Message ----- 
From: "Gordon" <gordon at n6wk.com>
To: <central-electronics at mailman.qth.net>
Sent: Saturday, September 07, 2013 3:21 PM
Subject: [Central-Electronics] CE-100V Scope


> Trying to get my scope working correctly.
>     When I start off in Standby, I show nothing on the scope, which 
> appears the way it should be.
> When I switch to operate, I get a *vertical* line, the completely across 
> the scope, from top to bottom.
> When I talk into the Mic and transmit, there is all Garble that appears to 
> the left of the line.
> It does not appear to be any sort of pattern.
> Is the line supposed to start off as vertical, or do I have my CRT clocked 
> wrong?
> Any ideas why the pattern is NOT a pattern? I have changed V21 with a new 
> 6U8, but no help.
>
> Thanks,
> Gordon
> N6WK
>
>
>
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