WEAK VIDEO OUT OF THE EARLY C64 326298 MOTHERBOARD Latest updates or corrections 7-13-2018 I always wondered why this particular motherboard put out such a weak video signal. I have four of them and they all do it. The early VIC chip itself has a characteristic flaw, vertical "ghost" lines that closely follow each screen character. That IC is the ceramic version 6567R56A and they all do it. The later CBM black epoxy case 6567 IC outputs clean video. However, the weak video persisted even after the VIC chip was replaced. I recently had some free time so I decided to find out why those early boards put out video that is faint and blurry. It turned out to be a factory mistake. There are several components between the output line of the VIC chip pin 15 and the two video sources (luminance and composite) that feed the A/V jack. There is a buffer transistor Q4 wired as an emitter follower, a low impedance source to drive the outputs. Measured with an oscilloscope, the luminance signal looked OK but the level of the composite output was less than half normal. It should be at least 1VPP at the jack when connected to a monitor. Looking at the schematics (I have several from different sources), they all show the value of resistor R10 to be 120 ohms, but in my four boards that resistor is 300 ohms! No wonder the video is so weak. There are two other resistors that are shown on the schematics but that don't exist on the boards, namely R48 and R49. The signal on coil L3 goes directly to pin 3 (no series resistor) of the video modulator and there is no resistor to ground there either. So, how do we fix the weak video problem? Inside the video cage, just to the right of the VIC chip, I connected a 220 ohm resistor across R10 to bring the video level up where it belongs. Easy and quick. (See photo) This old board now looks as good as the later version C64's. Ray