CTM-644 to Spectrum +3

[Velociraptor]

I'm trying to connect my CTM-644 to all 3 of my Amstrad micros - 6128, GX4000 and Spectrum +3.

After giving up on SCART switches I'm going to use a manual VGA switch. I've read that the Specky has the same 3 pins to connect but that the signal is too strong for the monitor. I have found advice to use a 330 ohm resistor when connecting it to SCART, but I know that SCART RGB is a lower level than CPC RGB. I've also read to turn the monitor brightness down when using the +3 output, that tells me that the signal is too strong.

Does anyone know what resistance to use on the RGB signals, and if sync also needs it?

[caver99]

i have yet to make the conversion cable to a plus 3 but will be doing once i get a 6 pin din for the video