-5V and 12V missing, TR5 blown

[hatman72]

Hi, I am after some advice on a poorly Issue 4S board that I have.

Measuring voltages on the 4116 chips 5V and 0V are fine, but -5 and 12V are missing (very low).

When I received the board C78 was already visibly blown so I replaced it. I also suspected that the voltage regulator was faulty so I replaced this. I replaced TR4 and TR5 for good measure and did a composite mod.

When I turned the board on the screen was dark grey with speckled white lines, while I was checking the voltages on the 4116 chips TR5 went up in smoke!

Does anyone have any suggestions as what could have caused this to occur?

Thanks

[hatman72]

I solved my own issue! I did not realise that the issue 4S has positions for two types of TR4 transistor. I had simply soldered my replacement TR4 into the original holes and this was wrong, so presumably caused TR5 to fry. Having replaced both, and used the second position for TR4 I now have a working board