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Replacement HD AV pack and internal install schematic, would like some feedback


SoftMachine
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I started working on an alternative to the HD AV pack but with added SPDIF RCA, as well as an internally mountable version with a 3d printed panel to snap or screw into the outer case if anyone would be interested in that. I liked the XOSVP's use of a VGA connector so I've included that and I see most designs with YPbPr output using 75ohm resistors, but are these actually necessary if my traces are wide enough to have an impedance of 75 ohms and will they make a difference on the L/R analog audio connections? I've only started learning this stuff recently so I'd like to know if anything about the schematic is no good. I'll post the design and editable PCB once I have it finalized.

schematic.thumb.PNG.a53eb5aacad265cb30299c4c71785f07.PNG

Integrally mounted version with DPDT switch to enable av mode 2+3:

schematic2.thumb.PNG.c5c93ddf3dc2e586354638f30ed35ee3.PNG

based on this diagram:

pinout.PNG.132bd51a69b539e69e1c9af19714da9f.PNG

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The left and right analog audio outputs do not need the 75 Ω resistors.  By the way, the symbol in your schematics (L) are inductors, not resistors (R).

 

The 75 Ω resistors are used for impedance matching of the 75 Ω coax that should be used to carry the analog component video signals: Y, Pb and Pr.  The analog audio outputs should not include them.

 

On the second schematic, the jacks you have on the Y, Pb and Pr signals are also no good.  You do not want a jack that has a built-in switch that is as shown shorting the video signal to ground when nothing is connected.  They only need to have two (2) conacts - the video signal and ground - not three (3).  Use an RCA jack like you did for the SPDIF connector.  You should be able to find a 3-position RCA jack panel with the jack's colored Green, Blue and Red.

 

Edit: Found some... I'm not sure of the quality of the products they make.

It would be nice it JKCR Electronics Co., Ltd. made a 2x3 instead of this 3x3 panel leaving off the left column of jacks used for composite video (Yellow) and stereo analog audio right (Red) and left (White) channels.

They do have a 3x1 RCA panel with component video color-coded jacks, a 5x1 that includes audio output jacks and an orange-colored RCA jack used for a coaxial digital audio (SPDIF) output.  The color doesn't actually matter but the various colors have been used to indicate the signal normally associated with it.

Green, Blue and Red - Component video signals Y, Pb and Pr

White and Red - left and right analog audio

Orange - coaxial digital audio

Yellow - composite video

 

Edit some more - reworded several times. 

And even more:

U1 in the first schematic better named J2 for jacks (connectors) instead of an electronic device (U?).

Same goes for the other items in both schematics.  J followed by a number for connectors and U followed by a number for electronic device(s) - like the TOSLink transmitter or other integrated circuits.

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Posted (edited)
On 8/12/2022 at 1:38 AM, KaosEngineer said:

The left and right analog audio outputs do not need the 75 Ω resistors.  By the way, the symbol in your schematics (L) are inductors, not resistors (R).

 

The 75 Ω resistors are used for impedance matching of the 75 Ω coax that should be used to carry the analog component video signals: Y, Pb and Pr.  The analog audio outputs should not include them.

 

On the second schematic, the jacks you have on the Y, Pb and Pr signals are also no good.  You do not want a jack that has a built-in switch that is as shown shorting the video signal to ground when nothing is connected.  They only need to have two (2) conacts - the video signal and ground - not three (3).  Use an RCA jack like you did for the SPDIF connector.  You should be able to find a 3-position RCA jack panel with the jack's colored Green, Blue and Red.

 

Edit: Found some... I'm not sure of the quality of the products they make.

It would be nice it JKCR Electronics Co., Ltd. made a 2x3 instead of this 3x3 panel leaving off the left column of jacks used for composite video (Yellow) and stereo analog audio right (Red) and left (White) channels.

They do have a 3x1 RCA panel with component video color-coded jacks, a 5x1 that includes audio output jacks and an orange-colored RCA jack used for a coaxial digital audio (SPDIF) output.  The color doesn't actually matter but the various colors have been used to indicate the signal normally associated with it.

Green, Blue and Red - Component video signals Y, Pb and Pr

White and Red - left and right analog audio

Orange - coaxial digital audio

Yellow - composite video

 

Edit some more - reworded several times. 

And even more:

U1 in the first schematic better named J2 for jacks (connectors) instead of an electronic device (U?).

Same goes for the other items in both schematics.  J followed by a number for connectors and U followed by a number for electronic device(s) - like the TOSLink transmitter or other integrated circuits.

Thanks a lot for the reply, I've changed the design based on your info. When it comes to connectors, 2x3 RCA with orange insulation is uncommon but after digging a little more, I've found CUI Devices RCJ-61675322 has a layout I can use based on its model number.

top: green, blue, red
bottom: orange, white, red

It's not stocked anywhere I've found so I'll have to contact Mouser about ordering. If I'm to wait a long time for delivery, I'd have to order in bulk which is pretty inconvenient. CUI has lots of connectors with model numbers relating to insulation color, so I've just used their connectors for the new schematics out of convenience. 

Do you think that an analog video amplifier like the THS7316 is worth the extra dollar or two? I don't know how much of a difference it would make.

 

xhdav_1.PNG.b4a183d519fda4a6479cacd2e79c9ec9.PNGxhdavi_1.thumb.PNG.21566d847d642dd596127f7a95f50a8d.PNG

Edit: Also, should the VGA connector housing be grounded or is that not appropriate? 

Edited by SoftMachine
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6 hours ago, SoftMachine said:

I've found CUI Devices RCJ-61675322 has a layout I can use based on its model number.

top: green, blue, red
bottom: orange, white, red

Not that the color of the RCA jacks matters but if you have Yellow instead of Orange someone's going to connect the composite video cable to that jack.

I don't think the video amp will be needed but best to try it before dismissing it.

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