Audio-video to USB connector

Thread Starter

ntt

Joined Apr 14, 2017
2
I have a cheap portable TV screen “Karowa 7” TFT LCD COLOR TV“ for which I would like to find some new use. The problem is it has an AVIN connector which seems to use USB as its physical connector.
https://s13.postimg.org/4tzxayi4n/image.jpg
I guess the TV has originally shipped with an adapter cable connecting the “USB” pins directly to (most likely) RCA audio and video plugs. Something like in https://forum.allaboutcircuits.com/threads/a-v-out-help-newbie-with-meter.63579/ but with different connector.

There are some USB to RCA cables available in eg. ebay but considering overall quality of the product (not very high) I wouldn’t be very surprised if it was some kind of custom design.

Top side of the PCB, the connector on right: https://s10.postimg.org/wjfxb0epl/image.png
Bottom side of the PCB, the connector on left: https://s9.postimg.org/s5eb1og33/image.jpg
The resistors R608-609 are marked 101, R601 is 472 and R602 is 102. I couldn't reliably measure the capacitors but they may be 600nF. Upper 3 wires go somewhere under the TV/TFT block so I don't knowhere they lead but the lowest wire goes to other side of the PCB(the wire in middle coming from right, going to R610):https://s18.postimg.org/kuuwntrzt/image.jpg
It seems to be connected to ground via resistors(223) and to the t1A transistor(assets.nexperia.com/documents/data-sheet/PMBT3904.pdf#page=3). From the transistor it seems to go to the ic on left: http://pdf1.alldatasheet.com/datasheet-pdf/view/440048/SANYO/LC863232C.html
As far as I understand, it seems to connect the IC's inputs to ground if it's signal is high.

How should I connect the pins (if it’s possible to know with this info) to RCA av cables(or to svideo, doesn't really matter as I wouldt need sound input)? Ask if additional measurements/photos are needed, I can upload them after weekend.
Thanks for help.
 

wayneh

Joined Sep 9, 2010
17,496
How should I connect the pins (if it’s possible to know with this info) to RCA av cables(or to svideo, doesn't really matter as I wouldt need sound input)? Ask if additional measurements/photos are needed, I can upload them after weekend.
Thanks for help.
If the connector is a genuine USB port, which is likely, the short answer is you cannot do this. Signals on RCA or S-video connectors are analog signals and that USB port is expecting digital signals. It's possible - but unlikely in my opinion - that your device uses a non-standard USB port to communicate analog signals. It's impossible to know without more information and maybe someone here can make that judgement from looking at the PCB. I can't.
 

Dodgydave

Joined Jun 22, 2012
11,285
Your easiest solution is to get s spare tv with a cvbs input (yellow phono socket) or scart socket, and bring a sreened lead out to the usb socket, connet the screen to ground, and probe the input to each one of the usb pins and see which one is the video, then do the same for audio.

According to the datasheet page6, for the Sanyo ic, pin 15 is the CVBS input.
 

djsfantasi

Joined Apr 11, 2010
9,156
There are high quality, inexpensive USB to either SVGA or HDMI converters available. We used them at work. I can't look for a link right now but if there is some interest I could look later.
 
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