Another National 505!

-
A non-working one of these came up for under £20 (delivered) on eBay and I figured it would be good craic seeing if I could fix it and add a composite video input.

It's a slightly different model (on the right) with a toggle power switch instead of rotary, but apart from that looks identical.

I found a brilliant video on YouTube detailing how to add a composite video input to a 1977 Panasonic television which turned out to have a very similar circuit.

UPDATE (13/02/22) -

All that was needed to get this going again was to replace a fuse on the main board. The problem was that someone had soldered a replacement fuse into the holder at some point and it wasn't rated highly enough. I sorted out the holder and put a 1.6A fuse in and off it went. 

I removed the UHF module and battery wiring and started adding a composite video input to this one. Above is an initial test using a signal from my trusty (repaired!) DVD recorder, but some tweaking is still needed. 

Comments

Post a Comment

Popular posts from this blog

Update on the touch monitor

-
This is tantalising... I found some data on driver chips used on these low-cost monitors and some of them have an I2C connection for sending pixel data directly to the screen. This may be to allow text or graphics overlay. Anyway the chip on my 7" screens is an AR05C-LF and there are millions of these in stock in the far east, but I can't so far find a data sheet for this chip or its sibling the AR05CA-LF. Being able to send digital pixel data via I2C directly to the screen would be, well, brilliant.
Read more

Apple iPad SSH Connection to Linux Laptop

-
Image
I was given this older Apple iPad a while back and was looking into installing Linux on it. Options are limited, but it is possible to install a shell to the iPad and run command line stuff.  SSH is always a bit of fun so I logged into my Linux Mint laptop remotely for a giggle. It was interesting running a few simple commands from the iPad. My cheapo Bluetooth keyboard came in very useful although I discovered that the iPad's OS version predated mouse support so the trackpad didn't work. Going a step further, I got my Raspberry Pi going again and was able to install VNC on the iPad and remotely control the Raspberry Pi's desktop. Could be useful! I'm also looking at fitting a small heatsink and 5-volt fan (recovered from a broken laptop) to the Raspberry Pi and over clocking it to 1GHz.
Read more

Six Inches - Big Enough

-
Image
I got around to taking the screen out of one of the LCD units to see what could be done with it. For a start the actual screen is 6.2" (according to the serial number and a ruler) not 7" as on the manufacturer's website, but that's no bad thing. It turns out a 6.2" screen is just the right size to fit in a double-DIN car radio slot, which prompts all sorts of ideas. It also turned out that there were 2 circuit boards, a big one with an audio amplifier and some power supply circuitry and a small one for the actual screen. Essentially the screen will operate with just a 4-wire connection (9 volt, GND, Video and Video GND). There is another connector for options (screen mode, colour and brightness), but with nothing connected to this the monitor defaults to perfectly use-able settings. In the photo I have it hooked to a PC via a VGA-to-Video adaptor. The computer is running Tiny Core Linux (my new favourite distro) in 640 x 480 mode (I think). It will go down to 320
Read more