Technics SA 5L Repair – Transistor Checks

Great..no manual for this thing..!

As the transistors (Q706-8?) on the main transformer board (which had the black scorch marks) fail with the Peak checker (as do the diodes) and don’t give definitive readings with diode mode meter except from the bases to collector/emitter (the diodes check ok too) they had to be desoldered using the Pro kit at work, as the most likely damaged part from an arc/burn. But the 3 tested ok…? Hmm..what now?

I soldered them back in using the typically inaccurate new 878D Chinese crap solder station with pointless temperature display that arrived today (220C – general soldering temp? Haha..set to 350C to get even a possibility of soldering a connection – and my free solder flux pen in a box of free goodies from a kind, retired old tech made my day! Classic: “..I’m getting too old and stupid..”). Know the feeling…:

All the capacitors in circuit check out with the Peak ESR meter, and the resistors in circuit give sensible readings so I’m not convinced I’ve found the problem was just black carbon shorting out power to this board as I can’t find a duff component…I want to check this board with the DC PSU first before I return it to the chassis and attach mains.

Before I do that I have to dismantle the entire horribly built thing to get to the main board for the rectifier and filter caps (they’re good with the Peak ESR).

Apart from a slightly broken resistor body I can’t see anything obvious on the main board either.

What an arse with no schematic…