Cambridge audio minx Go speaker


2020-01-19 5:59 pm
my Cambridge audio minx Go speaker no longer lights up.
the battery is well charged it gives 11v
if i stay press the power button there is just the red led that lights up behind and as soon as i release the button the led goes off.
It stopped automatically by itself after 30 min and does not light up.
No service manual.
Reset,I don't know how......
All chemical caps tested ok.
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Bwahaha, a 2013 portable Bluetooth speaker and it uses 4558 opamps. Sorry, I just found that combination rather amusing. And there's a zener follower regulator for their +7.5 V supply to boot. Oldschool. But it's cool to see some service docs for stuff like that for once.

Anyway, the external power supply input clearly says DC 16 V / 1.8 A. Have you been able to test that? (I imagine a 15 V supply would also be OK. CN901 on the board.)

If that doesn't work either, I would direct my attention to the area of the auto power down IC in the BT section (IC601 on schematic page 2). This is the guy that controls the red LED. Maybe it thinks there is no voltage? Check that C607 isn't shorted by any chance. (Ditto for C620, C621 just in case.)

Just to be sure, check +3.3 V at R612, both ends about the same, and that the resistor still measures 10 ohms. Probably all the case, the IC seems to be alive after all. And if BT+3.3 V is there, the BT+5V it is derived from should also be.

This comes from the IC901 area (#3).

When you plug in external power, USB+5V should be turned on. Could you test that?

If the battery sits there at 11 V, the question is whether the charge controller (IC903) starts doing its thing when external power is plugged in (voltage at R926). It would also be interesting to know what battery voltage is doing on attempted turn-on - if it collapses to <9 V, there's probably a cell that's toast.
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