Specta power questions

[turtlexiv]

Hey folks,

I've got a trunk mount Spectra (model T45ZXA5JC9AK) - a C9 radio which is using a C7-style control head.

I'm having difficulty in getting the radio to power up or show any signs of life. Reading at http://www.open.org/~blenderm/spectra/c ... ml#accj2j3 and http://www.repeater-builder.com/motorol ... mpers.html I'm understanding that I need to use the green and orange wires which emerge from the radio cable at the head end as my ignition sense wires (as opposed to pin 5 on the accessory connector), and of course the primary power going to the radio.

Hooked up in this manner (or even without the ignition sense) something odd is going on with the power when I turn on the DC power supply... the meter on the supply indicates a drop of voltage down to only 2VDC, and a current draw of about 2.5A. The radio itself shows no signs of life at all. What is going on here? Fearing that something is seriously goofed up, I haven't really wanted to try turning it back on for any further testing. The power supply is good - works as expected with a load other than the Spectra.

Any help would be appreciated.

[jackhackett]

Sounds like the supply is going into current limiting, indicating the radio is probably shorted. Put an ohmmeter across the power terminals on the radio and see if you read a short.

[turtlexiv]

I'm reading 16.11 kΩ.

[jackhackett]

Did you hook the radio to the supply the right way? If you swapped the leads it would draw a lot of current through the protection diode. Other than that I dunno.

[turtlexiv]

Ahh... the answer to this turned out to be exceedingly stupid. The seller of the radio provided me with the two-prong power cable to go with it. Turns out that the cable was exactly backwards, with red being negative and black positive. Go figure.

Thanks for the help

[57Shasta]

All hail the protection diode!

[Wile E. Coyote]

You can always tell when an electrician wires something in a car - all of the "hot" wires are BLACK!

~WEC