Watching NTSC videos on your PAL TV set

This is a quick HOWTO that may help a few people out there -- let me know if it does. I looked for this info,
couldn't find it on the net, figured it out myself, so, here it is...

I recently bought a new video machine, a Thomson, one of the new multi-standard jobs. It plays, according
to the documentation, PAL, NTSC and SECAM VHS videos. Uhuh. Yes, it does, but there's a catch.

Unless a video machine incorporates a scan converter (Note: this is a large, complex device) you can't get
real PAL video out from an NTSC tape.

(Start of somewhat technical bit)

There are three main differences between NTSC and PAL: Your multi-standard video machine can fix the first two, but not the last, you need the scan convertor for
that. For NTSC, the frequency is 60Hz (30 frames per second, interlaced) and for PAL it's 50Hz
(25 fps). What the video machine is putting out is known as PAL 60, also known as Quasi-PAL.
(Note: I stole this from

(End of somewhat technical bit)

OK, so you need to convince your TV to display PAL 60. I mean, if it was doing that already, you wouldn't
be reading this, right? Some TVs have a vertical hold control right there on the front panel, mine doesn't,
and I guess your's doesn't either.

(Start of screwdriver and soldering iron bit)

OK, so get out the screwdriver and dive into your TV set. NOTE: you can kill yourself here. If you don't
know what you're doing, stop, have a beer, buy a new TV set. It's cheaper than a funeral.

My TV set is a Sky TV, it has a Phillips chassis. The main do-almost-everything chip is a TDA4503. By
hit and miss I determined that the horisontal hold control is the 220k trimmer connected to pin 1. There's
a cap from somewhere (power?) to pin 1, and a 220k trimmer + 470k fixed resistor from pin 1 to pin 7,
which looks like it's ground. (Why didn't I measure what's power and what's ground? Because I switch off
and unplug the TV before I touch the PCB. And remember about all the capacitors, switched-off TVs have
killed people before.

So, I added a second trimmer, with a switch in parallel, into the circuit. Close switch, set NTSC, open
switch, set PAL. First mistake: the long wires to the switch pick up hum, causing the image to do strange
things. So, I moved the (new) trimmer to the other side of the 470k resistor, reasoning that the impedance
is lower over there. Worked, too.

Then, while performing the final tweek, my screwdriver slipped (HINT: insulate the shaft, as I belatedly did)
and shorted the trimpot rotor to a nasty big resistor - poof. Ah well, a new TDA4503 is < R30, so out comes
the old one, in goes the new one, tweeking gets done with an insulated screwdriver, and I can watch NTSC
movies. Magic.

So, remember to drop me a line if you find this useful. And, if your TV never works again, tough shit :-)

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