Am I correct that you're hooking into the blue SCART socket on the Philips VP415 laserdisc player?
If so then you need a different pinout from the one you listed above on a BBC to SCART lead but now that I've looked into this in a bit more detail, you probably need to jump through some other hoops...
I believe you need to use the following pinout, however the CUB's 'linear' (analogue) input is 0v to 4v peak-to-peak at 1500Ohms according to the service manual, whereas the standard output from the Laserdisc is just 700mv at 75Ohms, so you're likely to get an exceedingly dim picture, and I think your sync issue may be related too because even if you get the correct Pinout, you're going to be putting sync pulses at 1volt into the 74LS136 which has a minimum logic 'high' of 2v.
Therefore I think you're going to need a video amplifier (and sync amplifier) circuit to boost the levels sufficiently to work with the CUB.
There are a number of different earth/ground pins on the SCART including individual ones for each colour - I suspect they are all tied together on the PCB but either PIN 14 'earth' or PIN 17 'CVBS Earth' ought to do here as the CUB just needs a general reference to ground.
The 'SYNC' is actually the CVBS output and although the Philips service manual says it acts as Sync when used in RGB mode, I suspect it always the full CVBS composite video signal so there is a possibility that this might be too much for the CUB to handle and could result in it not syncing (just a guess here!).
Next time I'm working on a CUB I'll try to have a play with analogue inputs myself and let you know what I find. But that might be a while.
Thanks
Jonathan
If so then you need a different pinout from the one you listed above on a BBC to SCART lead but now that I've looked into this in a bit more detail, you probably need to jump through some other hoops...
I believe you need to use the following pinout, however the CUB's 'linear' (analogue) input is 0v to 4v peak-to-peak at 1500Ohms according to the service manual, whereas the standard output from the Laserdisc is just 700mv at 75Ohms, so you're likely to get an exceedingly dim picture, and I think your sync issue may be related too because even if you get the correct Pinout, you're going to be putting sync pulses at 1volt into the 74LS136 which has a minimum logic 'high' of 2v.
Therefore I think you're going to need a video amplifier (and sync amplifier) circuit to boost the levels sufficiently to work with the CUB.
Code:
SCART CUB 15 ---- RED ----> 1 9 ---- GREEN --> 2 7 ---- BLUE ---> 3 19 ---- SYNC ---> 4 14 ---- GND ---> 5The 'SYNC' is actually the CVBS output and although the Philips service manual says it acts as Sync when used in RGB mode, I suspect it always the full CVBS composite video signal so there is a possibility that this might be too much for the CUB to handle and could result in it not syncing (just a guess here!).
Next time I'm working on a CUB I'll try to have a play with analogue inputs myself and let you know what I find. But that might be a while.
Thanks
Jonathan
Statistics: Posted by PJTech — Wed Oct 02, 2024 12:53 am