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Andrew Tweddle

wrote:

On 6 Jun, 03:37, Andrew Tweddle
wrote:

Has anyone got a schematic or a method for adapting a Princess 4.5 inch
TV to AV in. I need a small composite monitor for an old machine.

Just a case of feeding it in after the tuner, and getting a point
where the signal is the right way up. I've done this with a bigger TV.
Thankfully miniatures normally run off an ext transformer, so no psu
isolation issues.

So the challenge is finding the right point, where the signal becomes
baseband. Output of tuner is where to start. I'd either scope the
possible points first, or maybe use a piezo with series R to check
they sound right, if theres any risk to a scope.

C/R etc might be needed to tweak the input signal to suit the tv, due
to dc offset. A cap on the input is good practice, as composite
outputs can have dc on them.

I'm not sure what else you need to know.

NT

I eventually found a schematic of the KA7511 IC that runs the TV and it
had a generic schematic, unfortunately it was unreadable. I then
followed your advice and scoped the IC to find pin 5 was the output from
the tuner which gave me a baseband video signal. I connected up an RCA
socket to this point and I now have an external picture running over the
normal picture. Next trick is to disconnect pin5 and insert the signal
and a switch in the chain.

Thaks for the help.
Andrew