I have a Roadstar tv-400n with the exact same chip inside. I wanted to get a uhf converter, but this seems a lot easier when some guy has already done a tutorial for you lol. Waiting for part 2
Finally ... still have quite visible horizontal retrace lines ... I wonder if powering down the chip (removing Vcc1 & Vcc2) might help ... ruclips.net/video/JJA79OBz9wc/видео.html
I'm looking at the datasheet schematic. Pin 5 is the correct one, but you will need to know two things to make this work. 1. The normal video level at that pin. 2. The signal polarity. You can get both by reconnecting the link, connecting the RF to your DVD player, and using a scope on that link. The circuit has a 2.1v P-P level after the 2SC828A emitter-follower amplifier, so 1v is probably pushing it well beyond that. The polarity will be pretty obvious on the scope, but not on the TV. An overdriven signal can look opposite of what is correct. If the polarity is wrong, you'll have to do a bit of work to correct it, but this check will at least tell you what you're facing before you do the connector work
Yep, that's what I was thinking of doing. At the moment I've connected in to where the pin 5 video signal output emerges. From what I can see it might pass through a capacitor (maybe) but then goes straight to the neck board via a blue wire. On the neck board it goes through a transistor so I'm suspecting that's where the amplification might be occurring.
Bill, do you have a RUclips channel or a website? I'd love to know more about doing this correctly. I normally work on audio equipment but I've ended up with a load of useless CRTs with no RCA inputs. Now I believe they are not so useless.
I think the input impedance must be 75 ohms to get the the correct video composit signal standard levels (synch . blank. black and white) in the TV side.
the horizontal lines and bright image suggest that the input intensity level is too high... may need a resistor to bring it down some...(maybe adjustable with a pot?) im wanting to RGB my old sony trinitron TV to run the CPC off.. but from what ive read its not RGB and 15khz compatible... (i should try to find the service manual for it!) ...i did notice theres a TV on FB marketplace for weeks now that has SCART... might be the easier way to go....
@@Colestamper1 I personally fixed this issue by disconnecting the rf input side of the video chip rather than the video out. that got rid of the retrace lines for me on 2 completely different sets.
@Brfff I figured it out. I ordered an amplifier with an volume knob now I'm gonna remove the volume knob from the amplifier and solder the original dail on the amplifier
@@thomasloode7711 There is also a "sound" pin on the IC, as well as the video pin, look at where that is on the PCB and that can be connected to for sound.
Yes, I do need to re-visit this one. Now that I'm more comfortable using the oscilloscope, I should be able to do a better, more permanent modification. I'll try to get to it this week (24-Jun-2024)
![🇹🇼 Princess PBW-121 (Adding Video Input to RF-only TV): Part 2 [TCE #0523]](http://i.ytimg.com/vi/JJA79OBz9wc/mqdefault.jpg)
![🇹🇼 Princess PBW-121 (Adding Video Input to RF-only TV): Part 2 [TCE #0523]](/img/tr.png)
I have a Roadstar tv-400n with the exact same chip inside. I wanted to get a uhf converter, but this seems a lot easier when some guy has already done a tutorial for you lol.
Waiting for part 2
Finally ... still have quite visible horizontal retrace lines ... I wonder if powering down the chip (removing Vcc1 & Vcc2) might help ...
ruclips.net/video/JJA79OBz9wc/видео.html
I'm looking at the datasheet schematic. Pin 5 is the correct one, but you will need to know two things to make this work.
1. The normal video level at that pin.
2. The signal polarity.
You can get both by reconnecting the link, connecting the RF to your DVD player, and using a scope on that link.
The circuit has a 2.1v P-P level after the 2SC828A emitter-follower amplifier, so 1v is probably pushing it well beyond that.
The polarity will be pretty obvious on the scope, but not on the TV. An overdriven signal can look opposite of what is correct. If the polarity is wrong, you'll have to do a bit of work to correct it, but this check will at least tell you what you're facing before you do the connector work
Yep, that's what I was thinking of doing. At the moment I've connected in to where the pin 5 video signal output emerges. From what I can see it might pass through a capacitor (maybe) but then goes straight to the neck board via a blue wire. On the neck board it goes through a transistor so I'm suspecting that's where the amplification might be occurring.
Bill, do you have a RUclips channel or a website? I'd love to know more about doing this correctly. I normally work on audio equipment but I've ended up with a load of useless CRTs with no RCA inputs. Now I believe they are not so useless.
Yea i think you need to add a 75ohm resistor in series with the socket
Do you think a 47 ohm would work
The idea is to impedance-match with the signal source to prevent reflections on the wire ... 75Ω is the standard
That is one of the coolest looking CRT televisions I've seen in awhile. would you be willing to make a 3D printable model available?
I'm happy to share whatever I can but wouldn't have a clue how to make a 3D model - one of the things I need to learn.
I think the input impedance must be 75 ohms to get the the correct video composit signal standard levels (synch . blank. black and white) in the TV side.
Yep - you generally want to impedance match to ensure optimal power transfer and reduce signal reflections
the horizontal lines and bright image suggest that the input intensity level is too high... may need a resistor to bring it down some...(maybe adjustable with a pot?)
im wanting to RGB my old sony trinitron TV to run the CPC off.. but from what ive read its not RGB and 15khz compatible... (i should try to find the service manual for it!)
...i did notice theres a TV on FB marketplace for weeks now that has SCART... might be the easier way to go....
I think it might be getting amplified on the neck board ... ? Will look further into it!
@@Brfff just try stickin a resistor on ya composite input from the vcr
@@Brfff Screen control on the flyback might need to be turned down
@@Brfffany update on this?
@@Colestamper1 I personally fixed this issue by disconnecting the rf input side of the video chip rather than the video out. that got rid of the retrace lines for me on 2 completely different sets.
@Brfff how do you suggest to solder the audio input
I really need to get back to this project - maybe this week?
@Brfff I figured it out. I ordered an amplifier with an volume knob now I'm gonna remove the volume knob from the amplifier and solder the original dail on the amplifier
@@thomasloode7711 There is also a "sound" pin on the IC, as well as the video pin, look at where that is on the PCB and that can be connected to for sound.
@Brfff this one
Yes, I do need to re-visit this one. Now that I'm more comfortable using the oscilloscope, I should be able to do a better, more permanent modification. I'll try to get to it this week (24-Jun-2024)
@@Brfff no rush. I'm about to do a similar mod to a late 70's early 80s set.
@@danielflakelar8193 Ahh, interesting. I think this one is supposed to be easier because it's got an IC that does a lot ... can't remember?
ruclips.net/video/JJA79OBz9wc/видео.html