Can't get tv to auto switch to AV channel

[Cannon Fodder]

I am using a 21" Samsung CRT television in my cabinet and have connected pin 8 on the scarf to 12 volts as I had read that this should get the tv to automatically switch to the AV channel. Unfortunately this doesn't work. Was wondering if anyone had any suggestions please?

[adder]

hmm, for the source of the 12v you are using, are you also sending the ground wire to one of the grounds of the scart plug? if not, do so

failing that im not sure what to suggest, u may need to read through this entire thread linked below to get some tips etc (its a large thread unfortunately):

http://forum.arcadecontrols.com/index.php/topic,77370.0.html

[apfelanni]

some tvs can be set to power on with av or p1 via the service menue . others offer the option to reroute av in to p1 .

[Cannon Fodder]

Thank you very much for the replies, I was being an idiot and hadn't grounded the 12v going to the scart, once I did this it worked fine.

[adder]

I hadn't grounded the 12v going to the scart, once I did this it worked fine.

good stuff. for anyone else reading this thread with similar problems here is some more advice below which i found from another thread on this forum:
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1) If you can figure out how to access the service mode of your TV, you *might* be able to set it so that it can automatically come on when you apply power.  Service mode, as the name suggests, is designed so that only technicians can get to it.  Generally you need the original remote, and instructions from the service manual (the one techs get, NOT the user manual supplied with the TV).  To further complicate this, service manuals are generally not made available publicly, only to registered techs.  The reason for this is because you can completely screw the TV up through making wrong settings in the service mode, so be careful.

2) If you have the remote, try turning the TV off with the remote and then cycling the power off/on.  Then, when you turn it on, it might come on 'fully' (if you are lucky).  Some variation of this theme might work for your TV.

3) Some SCART TVs will come on into AUX mode if you have 12v applied to pin 8.

4) If all else fails, you should be able to get the TV to come out of standby by pressing a channel button and/or the AUX button (perhaps labelled TV/AV).  A pain in the bum if you want to have a single power switch for your cab, but there you go.  If this is the case, and you are handy with a soldering iron, you could connect the button up to a momentary switch (eg standard arcade button) near your power switch, and press it just after you apply power to the cab.

Some power switches (including most standard TV power-on switches) include both a momentary switch (for signal voltages) as well as an always-on switch (for the mains voltage).  If you rig up an external power switch to your cab using one of these combined switches, then you *might* be able to use it to send a momentary signal through to your channel and/or AV button as you power the cab on.  I say *might* because you may actually have to wait for a second or two for the TV to power on before sending through the momentary signal to switch channel/AV mode, in which case you'll have to find another solution, perhaps involving a small capacitor (takes time to build up charge and therefore creates a delay before passing voltage through) or a relay.
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finally, here is another suggestion from me, which i used to get a 20" beko tv to always come out of standby automatically when mains power is switched on. what i did was i noticed that if i held down one of the buttons on the front of the tv (it was a channel/program button) while turning on the mains power, that the beko would now come on instead of being in standby. so, i simply filled the side of the plastic button with quick drying adhesive (or use super glue etc) and pushed (held) in the button until the glue dried. now the button is always pushed in (on). note: it does not affect my remote control which still allows me to change settings even though the button is always pushed in. (obviously if you want to do a neater job rather than use adhesive/glue on the button on the front of your tv, instead open up your tv and on the circuit board solder the the pins of the relevant little pushbutton together, so now pushing the button has no affect as it will now always be 'on')