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I have the 12v battery (it is actually 10 Ni-Cads in series), and, of course, it has a red wire coming from "+" and a black wire coming from "-".

However, on the schematic I am confused about whether the red wire should go to terminal 24, or the black wire. (It's the top line, with terminals 24 and 20.)

IRD 350 Schematic

I was changing the batteries and didn't take a photo of the connections first, and didn't see this battery was -12v, not +12v. Stupid...

Appreciate any help. This is probably very simple for anyone here, but I don't want to make mistake and bolax this instrument.

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closed as unclear what you're asking by Turbo J, Voltage Spike, Dmitry Grigoryev, Daniel Grillo, JRE Aug 5 '17 at 12:42

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Well, we can't help you from "bolaxing" the instrument. But there are some numbers on the diagram that indicate pins. you could get out a meter and start to probe out which connections are which. Like 19 is connected to S1004-F or 24 and 23 are connected to each other. I usually check the voltage on the pack to find the polarity. Good luck \$\endgroup\$ – Voltage Spike Jul 24 '17 at 15:41
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Since it's a -12V battery and based on the schematic, red wire should be connected with terminal 24 which is connected to the ground terminal.

Black wire need to be connected with terminal 20 for negative -12V battery.

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For whatever reason, your device requires a dual-rail supply. This is typical in, for example, audio power amplifiers.

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Audio amplifier with dual supply allows generation of AC signal for the loud-speaker without any DC offset.

However, on the schematic I am confused about whether the red wire should go to terminal 24, or the black wire. (It's the top line, with terminals 24 and 20.)

enter image description here

Figure 2. Coloured-up battery connections.

Hopefully the explanation of the reason for the dual supply above will give you the ability and confidence to finish the job.

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  • (24) = 0V (GND) = Red +
  • (20) =-12V = Black -

Check cell balance too or cell temp. be careful.

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  • \$\begingroup\$ I understand why the red would go to ground in this case, since the ground is +12v positive in comparison with -12v, but what's the reason for setting up the two batteries this way? Why aren't they just in series? \$\endgroup\$ – Fairbro Jul 22 '17 at 5:40
  • \$\begingroup\$ They are in series with center ground and +/-12V \$\endgroup\$ – Sunnyskyguy EE75 Jul 22 '17 at 5:43

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