no composite video

[paulclem1]

I have successfully installed the OS onto an 8gb flashcard. The pi works beautifully via an hdmi cable into my 32 inch tv screen. I've now purchased a small monitor for use with the pi to use on the composite video output. No picture! I have made sure that nothing at all is plugged into the hdmi socket BEFORE a reboot and ensured that the only thing I have plugged in is my composite video monitor. I have tried pressing "3" on the keyboard to activate composite video but to no avail. I have checked the output at the composite video connector using my pc oscilloscope, but there is only very low level noise there (50mV or less). I'm pretty desperate to get the pi working with the mini monitor as I have project do do for my school (yes you've worked it out - I'm a teacher, here in Thailand). Is there any way I can alter the config file to ensure that composite video is selected at boot-up? What I will say is that the monitor input impedance is 75 ohms (standard for a cv signal). I'm wondering if the cv output is man enough to drive into 75 ohms? Does the pi expect a high impedance input to the monitor please? If there is a hardware issue with this particular pi ( i note from this forum that other people have hadthe same problem, it isn't the end of the world (at least i hope not!) I can get hold of an HDMI to CV converter for a few quid from ebay and should, hopefully, be able to use that to drive my small CV input monitor. Can I have your fedback please as to what I should do!!!Many thanks, Paul

[Thebuilderdd]

On boot, press the 3 key.

[hoggbottom59]

Hi Paul

Incidentally I'm having problems with my PI but have no HDMI to check with.
It worked when I first got my pre-installed SD card but I decided to update it!

I found this information about the config file though so hope it helps you.
http://elinux.org/RPi_config.txt

Leon.

[FTrevorGowen]

I have successfully installed the OS onto an 8gb flashcard. The pi works beautifully via an hdmi cable into my 32 inch tv screen. I've now purchased a small monitor for use with the pi to use on the composite video output. No picture! I have made sure that nothing at all is plugged into the hdmi socket BEFORE a reboot and ensured that the only thing I have plugged in is my composite video monitor. I have tried pressing "3" on the keyboard to activate composite video but to no avail. I have checked the output at the composite video connector using my pc oscilloscope, but there is only very low level noise there (50mV or less). I'm pretty desperate to get the pi working with the mini monitor as I have project do do for my school (yes you've worked it out - I'm a teacher, here in Thailand). Is there any way I can alter the config file to ensure that composite video is selected at boot-up? What I will say is that the monitor input impedance is 75 ohms (standard for a cv signal). I'm wondering if the cv output is man enough to drive into 75 ohms? Does the pi expect a high impedance input to the monitor please? If there is a hardware issue with this particular pi ( i note from this forum that other people have hadthe same problem, it isn't the end of the world (at least i hope not!) I can get hold of an HDMI to CV converter for a few quid from ebay and should, hopefully, be able to use that to drive my small CV input monitor. Can I have your fedback please as to what I should do!!!Many thanks, Paul

Hi Paul, Did you install the O.S. (Raspbian?) via NOOBS or directly from a disk image (*.img) file?
In either case you probably need to edit a "config.txt" file to comment out or remove an "hdmi_force_hotplug=1" entry therein. The effect of that entry is to "turn off" testing of the HDMI connection for a "hot plug signal" (which some HDMI devices/cables fail to provide) and "force" HDMI mode regardless of whether an HDMI cable is plugged in. Depending upon your original install method both the location of said "config.txt" and the "editing" method are different. NOOBS, for example, provides its own editor in its "recovery mode" to do this: http://www.cpmspectrepi.webspace.virgin ... ting_Tools
Trev.

[paulclem1]

Thankyou very much. Yes I have installed NOOBS and it works a treat using my 32 inch hdmi tv! Very grateful to you, will edit the config file later today, hopefully your recommendation will cure the probem. I'm actually new to this, having only worked with pic assembler when I was in the Uk a few years back, so it's a new learning curve. I'm aiming to build some interface circuits for use with the pi such that i can control a 100mW laser beam to produce geometric shapes (vector scans) and get my students to write/alter programs that I write for the pi to produce different geometric shapes.
Will be in touch if I have any further problems getting the composite video signal to show itself!

[paulclem1]

Forgot to say, thankyou both Leon and Trevor for your help, will post the outcome of the "fix" in the next 24 hours or so. Regards Paul

[paulclem1]

Thankyou Trevor (and Leon!) have commented ot the "force hdmi" statement in the config file, and, hey presto, I have a great picture on my little 9 inch com,posite video monitor. the great thing is that if I reboot with the hdmi lead in , it will give me a signal on my tv (not that I'm likely to want that!). Genius! Thanks again and happy new year from Thailand, Paul. Do keep in touch, my email paulclem1@aol.com

[zsawyer]

Just a +1 on the solution

same issue.
a TV and extra cables were able to rule out a hardware problem.
I originally was able to use composite video, but flashed a newer version of NOOBs and the config file was the issue.
The newer version had "hdmi_force_hotplug=1"

The config file is well commented, just tweaking my overscan settings now. Thanks for the post and solutions.