How do I plug a Raspberry pi into a really old TV

September 4, 2019 4:15 AM

I think it's around 50 years old. I'm told that it works but I haven't plugged it in for fear of damaging it. Here's some pictures of the front and back. I have a raspberry pi model 3 b+, and I think it has a composite output through the audio jack. The plan is for an authentic NES emu setup.

I'm not qualified to open up the back. I don't take those warnings lightly. Are there things in there that are so old they'll need to be looked at before trying it?

posted by adept256 to Technology (10 answers total)

I think you're going to want an HDMI to RF coaxial converter. These can take the HDMI signal (including sound) and modulate it to a VHF signal that you can feed into a coax cable wired into those delightful screw connectors on the back of the TV. Shouldn't be any need to remove the back cover of the TV - you'd just need to switch it to 'external' for the aerial.
posted by pipeski at 4:24 AM on September 4, 2019 [2 favorites]

I think you can skip a step in pipeski's list, but you'll have to plug in the RasPi to an HDMI monitor to configure it first and force it to default to the composite output. Then you need one of these old boys to screw into those antenna screws, and you're off to the extremely antiquated races.

(Having said that, I apologize for bringing an "it should work" response to the green. I mean, it totally should work, but the internet is littered with unixy "it should work" information of little or no value, and I haven't personally done this specific thing. But please keep us informed, I'd love to know how this shapes up, it looks super cool.)
posted by mhoye at 4:48 AM on September 4, 2019 [3 favorites]

Composite to RF converter should work, consider testing it on a more modern CRT with composite input first. I also wouldn’t pry open the case, CRT fiddling is dangerous and er, fiddly.
posted by RobotVoodooPower at 5:05 AM on September 4, 2019

Nice find - that's an Australian-designed Pye portable TV from about 1969-1970. This thread's post 10 has a circuit diagram for one version; if that's correct for yours, it's a fairly modern design by 1960s standards - fully-transistorised, isolated-chassis, can run from a 12V car battery.

I would, however, be reluctant to power it up without getting it checked out by someone who's used to repairing vintage radios/TVs. It's very likely that it's in need of power supply (and maybe interstage coupling) capacitors being replaced by now, and it's better to get it checked out than to risk damaging the 1969-vintage transistors and flyback transformer which would be much harder to replace. It'll give a better picture if it's properly aligned too.

It doesn't have a composite video input, so to get a signal into it you'll need an RF modulator. If you can find an old VCR with a composite input and RF output then that's an easy option. And as it's an Australian set it'll want 625-line signals - in your Raspberry Pi's config, select PAL mode and turn off colour.
posted by offog at 5:27 AM on September 4, 2019 [1 favorite]

Get one of these RPi composite cables, plug it into your Pi, then plug the other side into one of these RF modulators, then run a coax cable from it to the TV and terminate it with one of these coax to 300 ohm adapters which hook into the aerial lead on the TV. Make sure the aerial lead switch is set to external, then tune the TV to the channel you set on the RF modulator (either 3 or 4). Enjoy!
posted by eschatfische at 5:39 AM on September 4, 2019 [2 favorites]

Response by poster: Here's my shopping list:

300 ohm transformer
AV to RF adapter
Raspberry Pi 2 Model B+ 3.5mm Port L/R Video 3 RCA AV Cable Line Cord N Q3X9

I found a place that does tv repairs but their minimum just to look at it is 77aud. Is that worth it? I can't find anything this old on ebay. It's made of wood.
posted by adept256 at 6:37 AM on September 4, 2019

Boy, it is not clear from that AV to RF adapter listing what's going on with that RF output, as that doesn't look like a conventional coax RF outlet. I see from offog's response that it's an Australian TV, and while I'm quite confident that the setup I recommended is OK for the US, you may need someone Australian to come in and say that's OK for your setup or to point you to the right cable.
posted by eschatfische at 6:47 AM on September 4, 2019

that doesn't look like a conventional coax RF outlet

I was about to say that's a BNC connector, but then I discovered I'd be wrong. It's a Belling-Lee connector which is apparently the standard in Europe and (I suppose) Australia. In the U.S./Canada we use the F connector instead.

Note that the 300 ohm transformer linked appears to have an F connector on it. It doesn't really matter which connector you go with, but they should match between the transformer and the RF modulator.

Also you'll need a coax cable (appropriately terminated) to link the two.
posted by neckro23 at 12:13 PM on September 4, 2019

Response by poster: Would this be the kind of thing I need that would fit between the av/rf modulator and the transformer?

I looked at the circuit diagram Offog helpfully posted and one of the few things I understand is on the mid-left hand side: EXTERNAL AERIAL 300ohms UNBALANCED.

As an aside, I'm in awe that people made these diagrams without CAD.
posted by adept256 at 12:34 PM on September 4, 2019

you'll have to plug in the RasPi to an HDMI monitor to configure it first and force it to default to the composite output.

You don't need to do this. The Pi will automatically output composite if there's no HDMI attached [unless it's been previously configured to force HDMI output].
posted by HiroProtagonist at 9:52 PM on September 4, 2019