---
title: "TS 1500 Composite Video Output"
id: "49203"
type: "post"
slug: "ts-1500-composite-video-output"
published_at: "2023-03-22T01:20:04+00:00"
modified_at: "2023-03-22T01:21:13+00:00"
url: "http://localhost/timex-sinclair/ts-1500-composite-video-output/"
markdown_url: "http://localhost/timex-sinclair/ts-1500-composite-video-output.md"
excerpt: "The TS 1500 video signal includes the back porch, a part of the video signal important to setting the black level and overall contrast. This is an improvement over most Sinclair ZX81 and some Timex/Sinclair 1000 computers, which did not..."
taxonomy_category:
  - "Timex/Sinclair"
taxonomy_post_tag:
  - "Hardware project"
  - "TS 1500"
taxonomy_indiv:
  - "Claudius Fatla"
---

The TS 1500 video signal includes the [back porch](https://en.wikipedia.org/wiki/Analog_television#Structure_of_a_video_signal)
, a part of the video signal important to setting the black level and overall contrast. This is an improvement over most Sinclair ZX81 and some Timex/Sinclair 1000 computers, which did not produce the signal.

[Composite video](https://en.wikipedia.org/wiki/Composite_video)
 output is available on pin 53 of the TS 1500 [standard cell](https://en.wikipedia.org/wiki/Standard_cell)
 logic device (SCLD). It is connected to diode D19 and then to a [voltage divider](https://en.wikipedia.org/wiki/Voltage_divider)
 formed by R1 and R2. The signal from the voltage divider the signal goes to the [RF modulator](https://en.wikipedia.org/wiki/RF_modulator)
, which produces a signal for older [analog televisions](https://en.wikipedia.org/wiki/Analog_television)
.

The modulator has 3 inputs. Starting at the top, they are: video input, power (+5V, middle), and channel 2/3 selection, driven by pin 54 of the SCLD.

## Modifying Your TS 1500

You’ll need a single NPN transistor like the 2N3904 and a short length of wire.

The modification is simple:

1. Remove the top from the modulator.
2. Cut-off the top (video signal) and middle (+5 volt) connections to the modulator.
3. Disconnect the RCA output jack.

Next, solder the transistor, inside the modulator, like this:

1. Pin 1, the base, to the former video signal input from SLCD.
2. Pin 2, the collector, to the +5V input.
3. Pin 3, the emitter, to the RCA output jack.
4. Replace the top on the modulator.

Last, bypass R1 and D19 by soldering a wire like the image below.

Thank you to [Claudius Fatla](https://github.com/McKlaud76)
 for the detailed instructions, photo and schematic illustration.

### Tags

[Timex/Sinclair](/category/timex-sinclair/)
[Hardware project](/tag/hardware-project/)
[TS 1500](/tag/ts1500/)

### People

[Claudius Fatla](/indiv/claudius-fatla/)

### About The Author

[David Anderson](/author/david/)
I'm a big fan of the Timex/Sinclair computers: my first was the TS 1000. I love building things for my TS 2068 and sharing them with others on this site and andertone.com.