What’s that? A transistor stopped my 8 V electricity flow? I’ve narrowed the missing rail down to the transistor stage, but that does not yet prove the transistor itself is the culprit.

We’re getting around 7.7 V going into this particular area of the circuit, but only about 0.05 V coming out. That’s hardly going to make the 7806 voltage regulator particularly happy, considering it needs a decent input voltage before it can produce its regulated 6 V output.

Increasing the supply voltage didn’t make any difference, so it was time to have another look at the circuit. Fortunately, I’ve got another Aiwa Mega-CD sitting here for comparison. Unfortunately, that’s the one with the horribly cracked circuit board. There’s always something!

Comparing the two boards revealed some differences between their revisions. The little transistor stage was arranged differently, and the component markings weren’t quite the same. I was looking at sourcing an A1290 replacement, but this was still a diagnosis in progress, not a confirmed transistor failure. More importantly, the other machine was getting approximately 8 V into its 7806 regulator and producing about 5.96 V at the output. Much more like it! At least now I’ve got a better idea of where to concentrate my attention.

The next challenge is tracking down a suitable replacement for the suspect component and seeing whether that gets things moving again. Another instalment of troubleshooting 101, otherwise known as poking things with a stick.