MomPC: add video and audio outputs to Combo VCR/DCD/TV ç Link to project’s blog.


Add video outputs project forum’s thread ç Link to project’s Q&A forum.


(This project is to add a 2nd TV flat screen to their environment connected to a source combo TV/VCR/DVD that does not have outputs (combos don’t). Very low cost is a driving factor. The patient has a MAGNAVOX 20MC4304/17 combo TV/DVD/VCR. The “motherboard” for this TV, where the input choices of AUX, TV Tuner, DVD, VCR have already been selected and are then converted to RED GREE BLUE (at around 6.5V each) and set on to the cathode tube CRT circuits. The part number is BTD850F01012 x4 Triple Main PCB Philips motherboard.)


The test image below is static but for the movie poster box (as shown below , A Space Odyssey: 2001) the movie box dissolves from one movie poster to another. These poster transitions are completely and clearly observable on the oscilloscope. The following scope captured photos show the video signal found from taking readings at the named jumper test point on the motherboard of this Philips motherboard.


Note: the scale and settings for the oscilloscope below were all the same, i.e., identical.


Note: for RED GREEN BLUE and (a) J1298 test point all correctly reflected the selection of AUX, DVD and TV as inputs, inputs that are internal to this Magnavox color combo TV/DVD/VCR/AUX.


To see the corresponding Magnavox motherboard with jumper test points – open the following in a new window:





BTD850F01012 x4 Triple Main PCB


Test image used for all scope test points, image is static but for the movie poster box.






J1298 Note: this is the SAME scale as the RED GREEN BLUE – about 1/3 lower voltage.

And about 2 times the voltage of the ext. v-in reading on jumper J1297 shown below.


J1297 Note: this is the SAME scale as the RED GREEN BLUE – about 1/6 lower voltage.