Fender Mini Deluxe Amp

MrChips

Joined Oct 2, 2009
35,159
The KIA6213S amplifier chip is a 9-pin SIP (single in-line plastic) chip.

pin-5 = GND
pin-7 = Vcc

Using a sharp X-Acto knife, cut the copper trace at pin-7 where it is indicated in red.
Turn on power and measure the voltage across the power input at the red and black wires.

Fender Mini 57 PCB.jpg
 

Thread Starter

Jsprite7660

Joined Jan 9, 2024
56
Thank you Mr Chips. I cut the trace there at pin-7 and measured across the power input at the red and black wires and see .543 Vdc. It returns to 9.45 Vdc when I switch it off. For my own learning experience can you explain why it's doing that?

Thank you
 

MrChips

Joined Oct 2, 2009
35,159
It means that we have to look somewhere else for something that is drawing too much current.
Remove the 8-pin op amp IC JRC4558 and test the supply voltage again.
 

Thread Starter

Jsprite7660

Joined Jan 9, 2024
56
The LED does not come on at all. It does work tho cus I lit it up with the multimeter across it to make sure it wasn't burnt out.

I will check those and get back to you thank you.

Quick question; if a capacitor was shorted, it would show a short while still in the circuit correct? Or do I need to pull them to be 100% certain.

Thanks
 

MrChips

Joined Oct 2, 2009
35,159
You can test for shorting capacitors while they are still in-circuit.
If the LED does not come on then pull C19 and test it out of circuit.
Test the board again for power with C19 removed.
 

Thread Starter

Jsprite7660

Joined Jan 9, 2024
56
Hey Les,

I don't have the exact Fender Mini '57 adapter. I have a Truetone 9VDC source that is capable of supplying 1700mA. I'm sure of the polarity and have bench tested the power adapter itself and on other devices as well.
 

Thread Starter

Jsprite7660

Joined Jan 9, 2024
56
Thank you very much. That was it!

I could have sworn I tried it both ways with jumper wires but apparently I got tunnel visioned. At least I got some short circuit trouble shooting experience.

Thanks a lot for the help everyone. You can roast me now if you'd like
 
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