Operation Manual

relatively easy way to check if this is the case in the form of two voltage test points.
To use the voltage test points, you’ll need a voltmeter or multimeter with direct current (DC) voltage measuring capabilities. If
your meter has multiple inputs for different voltages, use an appropriate setting.
Avoid touching the test probes to anything not labelled as a test point. It’s possible to bridge the 5 V supply that comes in to the Pi to the internal 3.3
V supply, creating a short circuit which can damage the device. Be especially careful around exposed header pins.
The two test points are small, copper-clad holes known as vias, which are connected to the Pi’s 5 V and ground circuits. Put the
positive (red) meter probe on TP1, located to the left of the board just above a small black component called a regulator labelled
RG2. Connect the black (negative) meter probe to TP2, located between the copper GPIO pins and the yellow-and-silver RCA
phono connector at the top-left of the board (see Figure 3-1).
Figure 3-1: The two voltage test points, labelled TP1 and TP2
The reading on the voltmeter should be somewhere between 4.8 V and 5 V. If it’s lower than 4.8 V, this indicates that the Pi is
not being provided with enough power. Try swapping the USB adapter for a different model, and check that the label says it can
supply 700 mA or more. A model rated at 1A is recommended, but beware of cheap models—they sometimes have inaccurate
labelling, and fail to supply the promised current. Genuine branded mobile phone chargers rarely have this problem, but cheap
unbranded devices—often sold as compatible adapters—should be avoided
If your voltmeter reads a negative number, don’t worry: this just means you’ve got the positive and negative probes in the wrong
place. Either swap them around or just ignore the negative sign when noting your reading.
Display Diagnostics
Although the Pi is designed to work with almost any HDMI, DVI or composite video display device, it simply may not work as
expected when you plug it in. For example, you may find that your picture is shifted to the side or not fully displayed, or is only
visible as a postage-stamp-sized cut-out in the middle of the screen or in black-and-white—or even missing entirely.
First, check the type of device to which the Pi is connected. This is especially important when you’re using the composite RCA
connection to plug the Pi into a TV. Different countries use different standards for TV video, meaning that a Pi configured for one
country may not work in another. This is the usual explanation for a Pi showing black-and-white video. You’ll learn how to