Recent content by Mark_W

Been working on this color classic on and off for a few days now, also spent some time reverse engineering the analog board, here are my findings: - Optocoupler near the smaller transformer (which outputs 60V, 24V and 8.3V and powers the CRT section) is for soft power only! It's NOT used for...

Ok it might seem ridiculous but I got it working! Bypassed the power supply section (desoldered transformer and switching mosfet) and connected 5v/12v/-12v capacitors to an atx psu, finally something showed up on screen. The image still has some stability issues and has hour glass distortion in...

Spent some time working on it this morning and noticed voltage on pin 6 drops to ~4v immediately after the power supply tries to start, then charges up slowly to 10v and next cycle continues. In theory the capacitor should be charged up by auxiliary winding through RP34 and DP15. They both...

Hello, I've been working on a color classics for a few nights now. Managed to fix the logic board after a recap, several trace repairs and a new DFAC-II sound chip. However, the analog board simply refuses to work. I've already recapped the analog board and replaced 2x TDA4605, 2xCNY17-3 and...

Btw this should be the correct position for t2 marker, to measure the end time of a complete cycle: Assume 50% duty cycle, the frequency should be 1/(t2-t1)=1/(800ns)=1.25MHz Or we can just use oscilloscope's default frequency measurement reading, it should take care of everything.

Grabbed my friend's se30 and removed rom, here's the result: Early revision with socketed cpu and pals. A2 is also 1.3mhz. And I think I know what's wring with the guide. Take a closer look at oscilloscope screenshot on pg 46, the frequency is calculated by 1/(t2-t1), but t2 is placed at...

I took another look at the repair guide: And on page 46 the scope shows square wave with 50% duty cycle, and its measurement is indeed 2.6MHz (pg 46): If ROM is installed, A2 will not show a perfect 50% duty cycle square wave, instead some irregular waveform as data is flowing on the bus (pg...

I opened my se30 again tonight as I noticed some of the smd 74hc logic ic legs are still a bit tarnished and reflowed all of them. While I'm at it I did more tests and found some interesting results. If I remove ROM stick and let it boot to horizontal bars, all frequencies on address lines are...

Hello @GreenBar0n, I have an se30 motherboard behaving just like your first one. Leaked capacitors didn't cause any damage but it was battery bombed. I had to repair about 10 traces near the battery socket and it was still stuck at simasima screen (horizontal bar as it has Ti vrams). All clock...