I have this Tatsujin PCB in my collection :
Some days ago I wanted to play it on my Astro City so, before rotating vertically the monitor, I tested the board on a supergun.Game was running absolutely fine but I noticed some wavy lines on screen as it was some kind of interference/noise:
I remembered I had same issue on some boards in the past and fault was due an electrolityc capacitor with increased ESR (the role of a capacitor is to block the DC filtering the AC ).So, with my ESR meter I went to test in-circuit the electrolytic capacitors and I came across a 470uF 16V one @C1 (the one that filters the +12V for the audio amplifier) with a high ESR :
You can see from ESR chart that a typical value for a 470Uf 16V electrolytic capacitor should be 0.2 Ohm while I measured 33 Ohm.So I desoldered and measured it out-of-circuit having confirm it was really bad (53 Ohm measured):
With a good capacitor fitted no more wavy lines and finally I could enjoy this cool shoot ’em up on my Astro City.