Sony Trinitron S-Video/Composite Mod (RF-Only TV) SOLVED

[Ryeno]

I did a SCART and S-Video mod on a Sony BA-1 Chassis. Both mods are easy to do but the S-video mod disables RF and Composite. I wanted those inputs to still work so I searched for a solution and, I found it, the TS5V330 video switch. The switch is self-explanatory except each, used and unused, source pin and each unused drain pin must have a resistor to ground or else the switch will not function correctly. The drains need 10 ohm resistors and the sources need 50 ohm resistors. The gist is that Y/C and CVBS (from the AV SW) will be fed into the THS7316 before the TS5V330. This is because the jungle chip on this unit expects a 2vpp signal and because the THS7316 allows us to connect the grounding resistors for the TS5V330. If you don't need the 6db gain then you could use 150/75R to drop the voltage back to 1vpp. Below is a partial write-up.

BA-1 chassis, based on the KV-20TS32, move R474 to R423 and move R475 to R424, to separate luma from chroma.

THS7316
Pull Y/C or S-video from IC402-1 or R480 and IC403-1 or R479 and connect them to the THS7316 RGB Amp pins 1 and 2.
Install a 0.1uF C0G capacitor into C438 and connect the negative end to THS7316-3.
All 3 inputs into the RGB amp should be AC coupled.
Only the Y/C outputs are AC coupled. CVBS output is DC decoupled. AC coupling did not work on the CVBS output.
0.1uF bypass capacitor.

TS5V330
Pin 3 and 6 are connected together.
* You might be able to DC couple all 3 inputs.
** I used 150 ohm resistors but 75 might work.

pin 1 - IN SW, pin 6 of MICON or R329 (10K) if MICON Pins 8 and 9 are rebuilt and s-video switch is jumped
Pin 2 - THS7316-8 through 220uF cap* & 150 ohm to ground**
Pin 3 - THS7316-6 through 75 ohm resistor & 75 ohm to ground
Pin 4 - IC402-7
Pin 5 - THS7314-7 C through 0.1uF>=* cap & 150 ohm to ground**
Pin 6 - Pin 3
Pin 7 - IC403-7
Pin 8 - 0.1uF cap to pin 16
Pins 9 & 12 - 10 ohm to ground
Pins 10, 11 , 13, & 14 - 50 ohm to ground
Pin 15 - EN SW, ground
Pin 16 - 5v

pics

[jeffez]

Nice work. I used a generic analogue switcher CD4053B. Two of them gave me six channels which was enough to handle s-video and audio switching.

[BazookaBen]

So how does this switch know to switch? It autodetects the live signal?

[vol.2]

So how does this switch know to switch? It autodetects the live signal?

"The CD405xB analog multiplexers and demultiplexers
are digitally-controlled analog switches having low ON
impedance and very low OFF leakage current. These
multiplexer circuits dissipate extremely low quiescent
power over the full VDD – VSS and VDD – VEE supply voltage ranges, independent of the logic state of the
control signals"

"Wide range of digital and analog signal levels:
– Digital: 3 V to 20 V
– Analog: ≤ 20 VP-P
• Low ON resistance, 125 Ω (typical) over 15 VP-P
signal input range for VDD – VEE = 18 V
• High OFF resistance, channel leakage of
±100 pA (typical) at VDD – VEE = 18 V
• Logic-level conversion for digital addressing
signals of 3 V to 20 V (VDD – VSS = 3 V to 20
V) to switch analog signals to 20 VP-P (VDD – VEE
= 20 V) matched switch characteristics, rON = 5 Ω
(typical) for VDD – VEE = 15 V very low quiescent
power dissipation under all digital-control input and
supply conditions, 0.2 µW (typical) at
VDD – VSS = VDD – VEE = 10 V
• Binary address decoding on chip
• 5 V, 10 V, and 15 V parametric ratings"

[BazookaBen]

So what does that mean you think? I'm still not sure how it's choosing the active input.

Was also curious how Ryeno's particular switch works

[vol.2]

It needs to see some voltage at pins 9,10,11 to switch on.

Spoiler

I don't know how he has it wired up, but all you need is to do is tweak the difference between Vdd and Vee to tune the voltage range for turn-on.

Spoiler

[Acilles]

I thought i might give an update. Here is my latest diagram minus the composite input. As BazookaBen pointed out, having composite the way i had it would affect the svideo signal. To use composite you would just need to use an external adapter.



Also i have revised my switching PCB. I was able to simplify the circuit by adding another CD4053B. The last one had some issue with it so i decided to just start again. Just waiting on fabrication. Hopefully it works this time and i can show how it fits in the above diagram.

hai jeffez. Can I request a copy of the gerber pcb file?

[jeffez]

hai jeffez. Can I request a copy of the gerber pcb file?

I'll have to dig it up. It was a while ago when I did this and I recall there was a small mistake on it which required running a wire from one pad to the ground plane. It's also not exactly well documented other than what you see in this thread.

[Vaporwave64]

Hello, I'm new to the Schmups forum, I hope this is the right place to reply. I have a Sony kv-20tr23, it has a BA-1 Chasis just like the one that was modded and share here in the thread. I would like to figure out how to get S-video from my set, I don't mind losing Composite/RF input. What's the easiest way to go about this?

[jeffez]

Hello, I'm new to the Schmups forum, I hope this is the right place to reply. I have a Sony kv-20tr23, it has a BA-1 Chasis just like the one that was modded and share here in the thread. I would like to figure out how to get S-video from my set, I don't mind losing Composite/RF input. What's the easiest way to go about this?

It looks like your set is RGB mod-able. I would just go with that.
https://sector.sunthar.com/guides/crt-r ... -ba-1.html

[jeffez]

For anyone that is interested, here is the gerber files for the PCB I made if they want to make it them selves. It takes the stock internal TV signals (TV_IN) and the new svideo and audio inputs you add on the back of the set (AV_IN) and outputs one or the other (TV_OUT) based on a HIGH/LOW input line on the PCB (labelled 'O' in TV_IN) . It's intended for RF only sets with Y/C jungle inputs but may have other applications.

NOTE - Use at your own risk as I am no expert and can't give any kind of guarantee I have got it running on my set with mono sound. The board supports stereo sound but I haven't actually tested that feature. There is also a mistake I made which requires connecting one of three pins to ground which I will mention below.

https://drive.google.com/file/d/1eiGlup ... sp=sharing

One of these 3 pins needs to be connected to ground.



Here is the parts list



INSTALATION
The idea is you are cutting the stock signals from the TV and redirecting them to this PCB (TV_IN) then connecting the TV_OUT pins into (essentially) where you cut the stocks signals from. The AV_IN pins are where your new input signals go. You can combine Y and C if you just want to run composite but it's probably better to use an external adapter for composite just so you can retain svideo (with it's better picture quality) as an option.

TV_IN (Stock video and audio signals from tv. In my case the Y, C and Audio from RF)
GND - Ground (From TV)
S - Sync from TV/Stock signal (Any signal that contains Sync such as composite or luma, may require some trial and error)
Y - Luma
C - Chroma
M - Mono audio (use either this or stereo (L R) inputs
R - Audio right channel
L - Audio left channel
O - HIGH/LOW signal. LOW will make TV_IN out put on TV_OUT. HIGH will out put AV_IN on TV_OUT. Can you a switch or in my case I used the HIGH/LOW signal from somewhere in the TVs mainboard that switches between 0v and 9v when pressing 'VIDEO' on the tv remote.
V - Voltage from the TV (in my case the 9v feed tapped of the TVs main board)

AV_IN (svideo and audio inputs you add to the back of the TV)
GND - Ground from inputs (connect audio and svideo ground together too)
Y - Luma
C - Chroma
R - Audio right channel
L - Audio left channel
NOTE L and R audio be mixed to mono and output on TV_OUT M pin if needed

TV_OUT (Video signals to connect to the jungle chip aswell as audio output for TVs audio circuit or and external audio output/speaker)
GND - Ground (From TV)
S - Sync input connection spot on TV circuit or jungle pin.
Y - Luma in on jungle
C - Chroma in on jungle
M - Mono audio output connection spot
R - Audio right channel output connection spot
L - Audio left channel output connection spot

NOTE again use at your own risk. I am no professional and this is really just a prototype I made just for my project. Another member on here asked for the gerber files so I decided to document my work incase someone else may want to use this.

For reference (as shared before) here is what the board looks like

[vol.2]

For anyone that is interested, here is the gerber files for the PCB I made if they want to make it them selves.

Thanks jeffez for the awesome contribution. I'm sure that a lot of people will find it helpful

[jeffez]

For anyone that is interested, here is the gerber files for the PCB I made if they want to make it them selves.

Thanks jeffez for the awesome contribution. I'm sure that a lot of people will find it helpful

Thanks. I can't believe it was in back in 2019 when I started on this and I made that PCB back in mid 2021, finally finishing the project around mid 2022. Life's changed allot since then but I still try to jump on here from time to time.