English Amiga Board - View Single Post - How would I hook the Amiga up to one of these?

jbilander · 20 February 2020, 11:49

Thanks. A quick look at the Philips CM8833 Service Manual says TTL level input Low 0V-0.8V, High 2.4V-5V...

https://www.manualslib.com/manual/74...33.html#manual

...so looks like you are good without using any resistor.

The reason for using a resistor in series with Csync is that it acts as a potential divider dropping the voltage level down to what more modern TV's expect (they normally expect a 1V peak to peak signal). What resistor value to use can easily be calculated with Ohm's law. You have 47 Ohm from the Amiga and normally 75 Ohm termination at the TV. The voltage level on the Csync signal coming from the Amiga is normally around 4.8V peak to peak, put in the values 4.8V, 47 Ohm, 330 Ohm and 75 Ohm in the calculator below and you end up at ~0.8V with using a 330 Ohm resistor. This is very well explained on Stedy's site http://www.ianstedman.co.uk/Amiga/am...iga_scart.html

https://www.rapidtables.com/calc/ele...alculator.html

20 February 2020, 11:49	#17
jbilander Registered User Join Date: Jun 2018 Location: Stockholm Age: 48 Posts: 270	Thanks. A quick look at the Philips CM8833 Service Manual says TTL level input Low 0V-0.8V, High 2.4V-5V... https://www.manualslib.com/manual/74...33.html#manual ...so looks like you are good without using any resistor. The reason for using a resistor in series with Csync is that it acts as a potential divider dropping the voltage level down to what more modern TV's expect (they normally expect a 1V peak to peak signal). What resistor value to use can easily be calculated with Ohm's law. You have 47 Ohm from the Amiga and normally 75 Ohm termination at the TV. The voltage level on the Csync signal coming from the Amiga is normally around 4.8V peak to peak, put in the values 4.8V, 47 Ohm, 330 Ohm and 75 Ohm in the calculator below and you end up at ~0.8V with using a 330 Ohm resistor. This is very well explained on Stedy's site http://www.ianstedman.co.uk/Amiga/am...iga_scart.html https://www.rapidtables.com/calc/ele...alculator.html