G'day all.
Back in 2012 I built a NBTV-oscilloscope circuit using the schematic from John Lawrence GW3JGA's site http://www.gw3jga.net/jl-notebook-082 but couldn't get it to work properly, was briefly getting a distorted silhouette picture at best at the time, but then it stopped displaying anything altogether and I got a small shaking smeary rough looking raster. I've revived the project recently and have been trying to work out what's wrong with it. I first traced over my wiring, found one mistake and fixed it which made no difference. I tried swapping chips to see if any were faulty, none are.
Then I did signal tracing and I found the NBTV signal turns to garbage after the input transistor as at the emitter output I get what looks like a carrier wave, and it goes downhill from there as most of the signals throughout the circuitry are garbage all the way except for video output Z which looks pretty much like the input signal. The weird thing is occasionally I was getting a rough field/line sawtooths and sync pulses but then it turns to garbage again. I was told to try connecting pins 1, 8, 15 to ground instead of -5V, that did nothing.
I am perplexed to what might be happening with my circuit as I've copied it to the T except I used a PN2907 transistor instead of a BC212 because I didn't have one and for the power supply I made a standard dual +-5V power supply using 7805 and 7905 regulators, bridge and filter caps and hooked to a centre tapped 10-0-10V transformer instead of the DC-DC converter because I didn't have one. I am wondering if my choice of power supply might be inducing noise into the circuit hence the carrier wave looking signal at the transistor emitter???
Anyhow attached are photos of my circuit, transformer and signals displayed on the scope. Here is a link to my latest video log of this project https://www.youtube.com/watch?v=RSJfvLQQqvU .
Any help on getting this circuit operational would be much appreciated.