TV to Oscilloscope conversion. - Page 1
Forum section: electronics / projects

author: Ferroto
author_rank: Frequent Contributor
timestamp: July 30, 2012, 06:31:34 pm
content: I saw a project awhile back where a TV was converted into an oscilloscope. Basicly on the back of a CRT there are two coils one that controlls the x deflection of electrons and the other that controls the y deflection. According to the tutorial all you do is connect the x defliction coil to a sawtooth generator and the y defliciont coil to your test signel.Recently I was at a yard sale and found an old portable black and white TV for 5 bucks and figured I'd give it a try.This is the tutorialI'm following. It tells me to connect the horizontal deflection coil to the location on the board where the vertical coil used to be but I want to be able to adjust the timebase which means some type of variable sawtooth generator I'm thinking a 555 timer. I still don't know how I'm going to do the triggering circuit.I was wondering has anyone here taken on this type of project before.

author: saturation
author_rank: Super Contributor
timestamp: July 30, 2012, 07:11:41 pm
content: In the 1970s, a TV to scope converter was my very first scope, but what I built included an RF modulator so the TV needn't be opened and hacked for safety reasons. You could also use any TV tuned to channel 3 or 4. The downsides were many, but it was cheaper to build then than buy or have nothing at all. Today, the quality will be far less than if you simply refurbished a used Tek. You could also do this with an old CRT monitor on the same principle.http://markbowers.org/home/crt-oscilloscope

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2012, 07:36:17 pm
content: The major issue with X-Y deflection coils is that real oscilloscopes use X-Y deflection plates (electrostatic instead of electromagnetic). I think the use of magnetic coils will produce major bandwidth and signal distortion problems.These days you could do much better by using a USB scope or a computer sound card and plotting the results on the computer display. For sure you would be limited to low frequencies, but I guess a converted television would have much the same limits.

author: EEVblog
author_rank: Unknown
timestamp: August 01, 2012, 11:49:02 am
content: It's a very 70's type project to build.Few would build one these days for anything useful, but I have seen a few recent builds around. Sorry, no links to hand.Dave.

author: deephaven
author_rank: Frequent Contributor
timestamp: August 01, 2012, 12:57:38 pm
content: The 'modern' way of doing it would be to create a frame store out of memory. This is then addressed with horizontal and vertical address counters which correspond to the H and V timing required to make a valid TV signal. The input side would write into memory to produce the desired display waveform.The above is a slightly simplified explanation of what would be needed!

author: RCMR
author_rank: Frequent Contributor
timestamp: August 01, 2012, 09:56:37 pm
content: Wow... brings back memories.Back in the 1970s I made a lot of beer-money by converting old B&W TV sets into oscilloscope-like displays that were very popular at discos.You'd simply hook the Y-axis of the yoke up to the output of the audio section (ie: instead of the speaker) and feed the music into the top of the volume pot.The X-axis of the yoke would be hooked up to the output of the vertical output stage (thus giving a 20mS scan rate).Some strips of coloured cellophane over the front of the mono CRT and you'd get a truly excellent multi-coloured oscilloscope-like display.I'd buy the old TV sets for about $20 each and sell the "DiscoWave" units for about $50 each (remember 1970s dollars). I used to earn about $50/hour doing this and couldn't keep up with the demand.Works really well for audio frequencies.