AVR-Chat

Arif -

The tube should be fairly tolerant of ripple on the high
voltage. There is proabably something else going on.

Watch out for your transformer! It can generate a magentic
field that effects the tube.

Jim


On Wed, 7 Dec 2005 11:45:19 +0200
 "Arif YILMAZ" <arif.yilmaz@bilten.metu.edu.tr> wrote:
> Thank you Mike and Jim, 
> I am driving the crt in XY  mode I don't use any raster
> actually I used
> a previously available schematics for the tube,   the
> power supply may
> have problems as you stated, I previously inspected those
> signals and,
> tube is driven with 1400 volts anode-cathode voltage,
> however there is
> about 20 volt ripple on it because it uses typical diode
> -capacitor
> voltage doubler circuit stages to obtain 1400 V from a
> 170 AC winding of
> the transformer. Other parts of the circuit also use 7815
> Voltage regs.
> Etc. and their output seems very clean when inspected on
> the scope, , X
> and Y deflection amplifiers have transistor stages, and
> they produce
> very stable x and y signals  ie. Horizontal, vertical, 
> When I inspect the tube datasheet I see different anode
> terminals like
> A1 A2 A3 , and single cathode terminal, 
> 
> By the way, I showed special care to ground loops in the
> board and still
> there may be problems you may be right, also routed its
> signals with at
> least 36 mils width, and 72 mils for ground signals. 
> I am now inspecting the board but not very sure if it is
> going to help, 
> 
> Do you think tube pyhsics are so intolerant to 20 V
> ripples on the
> anode voltage?  The flickers when signal is moved upwards
> are due to
> it?, I will   put a high voltage capacitor there...
> 
> 
> 
> 
> 
> 
> 
> -----Original Message-----
> From: AVR-Chat@yahoogroups.com
> [mailto:AVR-Chat@yahoogroups.com] On
> Behalf Of Jim Wagner
> Sent: Tuesday, December 06, 2005 9:08 PM
> To: AVR-Chat@yahoogroups.com
> Subject: Re: [AVR-Chat] Driving Oscilloscope CRT like
> Memory Mapped
> Graphic Display
> 
> 
> Arir -
> 
> Here is some more information about CRTs. 
> 
> Magnetic susceptability (interferance) is very common
> with
> CRT. Most manufacturers put a metal magnetic shield over
> the tube. Often, it is a special metal (one has a trade
> mark of "mu-metal", I believe). With home TVs, the color
> ones are more critical for external magnetic fields.
> There
> is usually a "degaussing" circuit that demagnetizes the
> CRT every time
> it goes on or off. 
> 
> There is a big trade-off between accelerating voltage and
> many other things. The spot becomes brighter with higher
> voltage. But
> the beam becomes more "stiff". This means that it takes a
> higher
> deflection voltage (if it is electostatic deflection).
>  It is common
> practice to run the deflection plates near ground to make
> connection to
> circuitry easier. This means two supplies, however, one
> for the cathode
> and one for the screen. It is common to use
> high-frequency oscillators
> for the high voltage (that is, switching power in modern
> terms). Because
> the voltage is quite high (5-10Kv), the transformers tend
> to be
> difficult to make. 
> 
> All of these factors (and many more, including weight and
> size) have contributed to the modern trend of using LCD
> for oscilloscope
> displays. 
> 
> Jim
>
---------------------------------------------------------------
> The Think Different Store
> http://www.thinkdifferentstore.com/
> For All Your Mac Gear
>
---------------------------------------------------------------
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 
> 
> ------------------------ Yahoo! Groups Sponsor
> --------------------~--> 
> Get Bzzzy! (real tools to help you find a job). Welcome
> to the Sweet Life.
> http://us.click.yahoo.com/KIlPFB/vlQLAA/TtwFAA/dN_tlB/TM
>
--------------------------------------------------------------------~->
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 

---------------------------------------------------------------
The Think Different Store
http://www.thinkdifferentstore.com/
For All Your Mac Gear
---------------------------------------------------------------