problem tdi sl ,inversion battery

[tifred]

Hi everyone.
My friend has a problem with his TDI SL. He reversed a battery in his battery pack, and his TDI SL won't start anymore.

We changed the battery and checked that the batteries were properly inserted; I'm getting 12V at the positive terminal. The TDI still won't start. I'm afraid he's fried his TDI. What component or procedure should I use to try and find the problem?

Thanks for your help.

[Carl-NC]

Reversing one or even a few cells in the pack will cause the pack to have low voltage but should not damage the SL. If he reversed all the cells then the SL still has reverse battery protection and should not be damaged. The protection devices are Q8 and Q24 so I would start by seeing if they have any visible damage.

[Carl-NC]

Here is the schematic of the power supply:

[tifred]

Thanks Karl,

I'll try to control that.

[Op04]

Dear Carl,

Sir, by your latest schematic it seem current limited by 1.7A, what if I put standalone 20V 3.5A supply for coil only (not through that mosfet on/off switch) and add more 3.3R 25W before coil to get more faster tx on and longer flat time before off, or assumption desired coil current 3A will minelab mono coil survive?

[tifred]

Here is the schematic of the power supply:

Here, I changed the two FQT7N10s (Q8, Q24) and then the transistor on Q20 next to the LM386 (very low audio), and there was 0.9 volts on the LM386 power supply. Everything works!"