[Central-Electronics] CE-100V Scope

[Gordon]

Hi Stu,
  I replaced all the 2.2 meg, the 470k and the 100k Resistors and the 
.01 caps that are on the tube socket bracket.
Everything there is new. I verified the 500K and the 100K pots are good 
for the Focus and the intensity.
I have tried another 6U8, but no change.
I get a vertical line , completely top to bottom when I push the PTT in 
*any* mode with or without a Mic connected.
In AM, I think there might be a Trapezoid pattern, but if so,it is off 
the top of the screen, so I can not really tell.
I replaced the 50PF Cap that is under the finals, but no change.
I am enjoying restoring this 100V, but it sure has become a lot of 
Work!..LOL

73,
Gordon
N6WK


On 9/7/2013 11:31 PM, w7fe wrote:
> 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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