RPi to old TV set up...

[Dazzathedrummer]

Hi,

My wife and I have just bought a 60's/70's Sony Trinitron CRT TV that's in perfect working order.

My plan is to somehow use an RPi to display YouTube, iPlayer etc and to screen share Apple Movies from an iPad - and, of course, play games on Retropie.

There are quite a few projects around the internet that do exaclty that but with varying results and using a wide array of contraptions to get from the composite out of the Pi to the RF input of the TV - I'd just like to check that what I'm about to buy is going to do the trick and if not get some sugestions for devices that would be better suited.

So, I've looked at HDMI converters and most things that I click on seem to be out of stock with Amazon so, going down the composite route...

One of these from Pi Hut - https://thepihut.com/collections/raspbe ... spberry-pi

This will get me from the pi to composite RCA. The next step seems to be more complicated.

This... https://www.amazon.co.uk/Converter-Fema ... 688&sr=8-6
claims to do the trick but there's a few dodgy reviews and the one good reveiw left me confused as to whether it will work or not for what I'm doing.

There seems to be a lot of devices that go the other way (scart to HDMI, Composite to HDMI) but much that outputs RF coax.

Would be great if anyone can point me in the right direction on this.

Just to confirm, the TV only has an RF coax input.

Thanks.

[hippy]

A/V jack to phono, then phono to RF is what you need.

Can't recall what the spec would need to be but I also believe it should be UHF rather than VHF in the UK; 400-800MHz (ish). You don't say where you are so it might be different for you.

I have tended to use camcorder RF adapters and satellite receivers designed for the UK market so they just work but those are pretty rare these days.

The quality of RF will likely be significantly reduced compared to raw composite.

[neilshep50]

Your recent TV purchase will be 625 line display, so at best you are looking at 800x600 resolution. This would allow you to play YouTube videos in 480p maximum.

The modulator on Amazon might be OK. The bad reviews may be from people trying to use them on modern tv's that do not have analogue mode enabled. Our 2018 Panasonic still has analogue tv tuning, but you have to specifically find the feature in setup to turn it on.

I found this on Fleabay: https://www.ebay.co.uk/itm/Jebsee-SM-21 ... SwrVpfA0Ne This has a SCART input, but there are readily available composite to SCART adapters. If you are prepared to go secondhand, then looks like a viable option.

[rpdom]

Your recent TV purchase will be 625 line display, so at best you are looking at 800x600 resolution.

I wouldn't have thought so. SD TV is 576i. Although 625 lines are transmitted, many of them are not displayed. Some of them carry data like the channel ident and time signal.

[drgeoff]

If you still have an old VHS recorder up in the loft you can use that as an RF modulator. Even if not the final solution it will let you see if the achievable result meets your quality requirements. If it doesn't, don't waste your money buying other RF modulators because they will not be any better.

You'll need the 4 pole 3.5mm plug to 3 phonos cable and possibly a 3 phono to SCART adaptor. Note that the adaptors come in 3 versions:

1. For signals coming out of a SCART socket.
2. For signals going into a SCART socket.
3. With a switch to select either of the above two.

Obviously the first of those three will not be appropriate.

[TheFireman]

Pictures and description of that Amazon RCA <-> RF co-ax adapter show 61.25MHZ and 67.25MHZ output.
61.25MHZ is TV VHF channel 3...
67.25MHZ is TV VHF channel 4...

N.B. these assignments are valid for the Americas, and a few Asian countries.

If your Trinitron is made for the US market, this will work.

Otherwise, YMMV

[Dazzathedrummer]

It’s a UK TV - we’re running a vintage games console on it at the moment.

6D3EFAB5-C701-42BE-B323-70BE1EA33C0A.jpeg (117.65 KiB) Viewed 505 times

[drgeoff]

One of the original "PAL patent avoiding" Sonys. The Hue control is the clue for that. Model no. something like KV-1320UB. I still have an even earlier 1300UB model. Black case without the speaker grille panel left of the 1320 screen. Speaker on right below the tuning knob and controls.

Both models have a chassis that is not mains isolated. The headphone sockets on the 1320 are fed from an audio transformer to isolate them from mains.

[Dazzathedrummer]

One of the original "PAL patent avoiding" Sonys. The Hue control is the clue for that. Model no. something like KV-1320UB. I still have an even earlier 1300UB model. Black case without the speaker grille panel left of the 1320 screen. Speaker on right below the tuning knob and controls.

Both models have a chassis that is not mains isolated. The headphone sockets on the 1320 are fed from an audio transformer to isolate them from mains.

Yep - this one’s a 1330UB, serial number in the 12,000’s.

I didn’t know about the mains isolation (or lack of it) ...I won’t be fitting the RPi to the inside then!!
There’s a red button on the back that cuts the whole thing off - I guess that’s some kind of panic button!

[hippy]

There’s a red button on the back that cuts the whole thing off - I guess that’s some kind of panic button!

Possibly a resettable fuse for when things do go bad.

[dustnbone]

It's usually very simple to add a composite input to these old CRT TVs, there was just no demand for it at the time they were produced. Just be careful working inside a CRT set. Zappy Zappy sad

[davidcoton]

It's usually very simple to add a composite input to these old CRT TVs,

True but not a good thing to do, as you said...

Zappy Zappy sad

Even if you don't get a shock, the chassis not being isolated from mains will result in potential destruction of anything connected, and a shock risk to anyone touching the connector or connected equipment.

DO NOT ADD ANY EXTRA CONNECTIONS TO OLD TELEVISIONS
unless you know that the chassis is isolated, or you can design mains-proof isolation into your connection (that is NOT simple).

[drgeoff]

There’s a red button on the back that cuts the whole thing off - I guess that’s some kind of panic button!

Possibly a resettable fuse for when things do go bad.

Correct.

[drgeoff]

DO NOT ADD ANY EXTRA CONNECTIONS TO OLD TELEVISIONS
unless you know that the chassis is isolated, or you can design mains-proof isolation into your connection (that is NOT simple).

+1

[dickon]

What I want to know is, WTAF were they thinking connecting the chassis to neutral (if I've understood the other thread on this basic topic well enough)? There must have been a reason, but for the life of me I can't see it.

Apologies, JamesH, for being off-topic, but this is a public-safety thing.

[hippy]

What I want to know is, WTAF were they thinking connecting the chassis to neutral

Easiest way to get a high voltage with respect to Neutral -- or what some would insist these days is "ground"

I believe some did not have the chassis direct to Neutral but used a virtual chassis derived from rectifying Live and Neutral for higher voltages. Still equally dangerous AIUI because it wasn't transformer isolated.

[drgeoff]

What I want to know is, WTAF were they thinking connecting the chassis to neutral (if I've understood the other thread on this basic topic well enough)? There must have been a reason, but for the life of me I can't see it.

Maybe you are too young!

This was circa 1971. Electronic components were significantly more expensive in real terms than now. Switch mode power supplies were virtually unheard of in consumer equipment. Mains transformers operating at 50 or 60 Hz powering a TV would have been expensive, bulky, heavy and needed magnetic shielding. Non isolated chassis had been the standard way of powering a TV for decades. The plastic/wooden case was designed to prevent touching the chassis. The only exposed metalwork was the aerial socket and that had a very small capacitor - a few tens of picofarads - in series with both legs. That Sony model with the headphone sockets was a rare exception.

There was a brief period when people tried getting audio from TVs into Hi-Fi systems by inserting a coil to pick up the 6 MHz intercarrier and taking it to an external unit for FM demodulation.

Because of non-isolated chassis there could be no AV inputs or outputs, no SCARTs. The only way in was RF. That is why the early home computers had RF modulators. VCRs had RF modulators. Satellite STBs had RF modulators. On-Digital Digital Terrestrial STBs had RF modulators. Games consoles had RF modulators. Camcorders were supplied with RF modulator units. Etc.

[pidd]

What I want to know is, WTAF were they thinking connecting the chassis to neutral (if I've understood the other thread on this basic topic well enough)? There must have been a reason, but for the life of me I can't see it.

Apologies, JamesH, for being off-topic, but this is a public-safety thing.

Chassis wasn't necessarily at neutral, sometimes it was live, equipment often had reversible two pin plugs, and sometimes they were plugged into light sockets which again weren't polarised.

Don't forget that up to around 1960 some of the UK still had DC mains, equipment couldn't use transformers straight off the mains so a lot was done with dropper resistors. With it being valve technology it was all high voltage and low current apart from the valve heaters which were wired in series. The DC technology was well established and took a while to disappear from equipment.

Our local substation was one of the last to go to AC, some years before hand it had been reconfigured to convert AC to DC with a rotary converter, prior to that it was presumably just a switching station. It was definitely DC in 1956 but I can't remember exactly when it went AC.

[cleverca22]

Both models have a chassis that is not mains isolated. The headphone sockets on the 1320 are fed from an audio transformer to isolate them from mains.

ive got a pair of much more modern (IR remote, on-screen display for the channel and color settings) CRT's and i'm pretty sure they also lack mains isolation

my dad once blew one up just by plugging it into the wall when i was ~5, the plug is properly polerized, but the socket in the room wasnt, and the "neutral" was shorted to the coax shield, so you can see what could go wrong...

i dont know how (i was ~5 at the time), but he did get it repaired at a shop, and it works fine now

[DarkElvenAngel]

What you are looking for is called an RF-Modulator

They take composite in and coax out.

[aBUGSworstnightmare]

You need some UHF modulator i.e. like this one : composite and audio in, UHF out

IMG_20200711_082354.jpg (54 KiB) Viewed 269 times

IMG_20200711_082402.jpg (37.58 KiB) Viewed 269 times

I'm pretty sure I have the users manual still around but could not find it yet .. (as it also allowed for changing the channel)

[Dazzathedrummer]

It's usually very simple to add a composite input to these old CRT TVs,

True but not a good thing to do, as you said...

Zappy Zappy sad

Even if you don't get a shock, the chassis not being isolated from mains will result in potential destruction of anything connected, and a shock risk to anyone touching the connector or connected equipment.

DO NOT ADD ANY EXTRA CONNECTIONS TO OLD TELEVISIONS
unless you know that the chassis is isolated, or you can design mains-proof isolation into your connection (that is NOT simple).

Don’t worry - I’m not going to be taking the back off!!

[Dazzathedrummer]

You need some UHF modulator i.e. like this one : composite and audio in, UHF out
IMG_20200711_082354.jpg
IMG_20200711_082402.jpg

I'm pretty sure I have the users manual still around but could not find it yet .. (as it also allowed for changing the channel)

Typing ‘UHF Modulator’ into Amazon has thrown up a lot more options than ‘RF Modulator’ - thanks for the tip!

[Dazzathedrummer]

All sorted!

I bought one of these RF modulators from eBay ...

2B953B15-0CC7-42B8-A540-D1B6979D5B4F.jpeg (83.4 KiB) Viewed 88 times

I’ve changed a few things in the config.txt to get PAL output to composite and to size the screen (it still needs a few tweaks).

Here it is with the Pi 3b (BBC test card ‘f’ as the desktop background)...

84C76153-F1BC-44F4-84C9-7BCA072679B2.jpeg (105.68 KiB) Viewed 88 times

We’ve been watching old episodes of Steptoe & Son on YouTube...

E6554C31-164A-4ACE-A5CF-D44516AF1B54.jpeg (128.55 KiB) Viewed 88 times

Next step: adding rPlay for Apple Airplay support.