Pin 13 on Maxtrac (SW A+)

[sailor]

Hi,

I've been using pin 13 to power a small active device for a number of months. Suddenly, while nothing has changed I no longer have 12V out on this pin. Radio is set for ign sense, and still powers on fine. Just no power out on 13. Is there a fuse for this internally?

Thanks!

[Satelite]

Hello :
There is no internal fuse for pin 13 that i see on the schematics.
But id suspect component U402-1 to be at fault and needs checked out to see if its gone bad.
The sw A+ is fed from it to pin 13.
You mentioned 12 volts out of it but i see on the scematics its rated at 5 volts so youd be over driving the voltage regulator.
Nice thing is its on the top side of the 16 pin HLN9313 logic bd.
Its located with the radio facing you in the bottom most left corner of the logic bd.
It will have 5 legs on it soldered to the bd with a metal tab that a screw goes through to hold it tight as well as hold the logic bds bottom left corner solid to the chassis.
Looking at my bd the component says on it .
m mc 33267th qgy617
This is the same regulator used on a maxtrac 5 pin logic bd if you wanted to rob one for repair.
Of the 5 legs on the regulator the 1st leg closest to the bds lower egde being power in and the middle 3rd pin being ground and the furthest 5th pin being power out .
You can test for power in and out on the regulator before replacing it.
Obviously if you have power out of the voltage regulator you then more than likely have a burnt open trace on the bd going to pin 13 id suspect.
If no power into pin 1 of voltage regulator then check J8 - 5 for power going to regulators input.
Its trace is actualy on the bottom side of the logic bd.
Motorola part number = 51-80942T01
Good Luck.
Satelite

[kcbooboo]

Hello :
There is no internal fuse for pin 13 that i see on the schematics.
But id suspect component U402-1 to be at fault and needs checked out to see if its gone bad.
The sw A+ is fed from it to pin 13.
You mentioned 12 volts out of it but i see on the scematics its rated at 5 volts so youd be over driving the voltage regulator.
Nice thing is its on the top side of the 16 pin HLN9313 logic bd.
Its located with the radio facing you in the bottom most left corner of the logic bd.
It will have 5 legs on it soldered to the bd with a metal tab that a screw goes through to hold it tight as well as hold the logic bds bottom left corner solid to the chassis.
Looking at my bd the component says on it .
m mc 33267th qgy617
This is the same regulator used on a maxtrac 5 pin logic bd if you wanted to rob one for repair.
Of the 5 legs on the regulator the 1st leg closest to the bds lower egde being power in and the middle 3rd pin being ground and the furthest 5th pin being power out .
You can test for power in and out on the regulator before replacing it.
Obviously if you have power out of the voltage regulator you then more than likely have a burnt open trace on the bd going to pin 13 id suspect.
If no power into pin 1 of voltage regulator then check J8 - 5 for power going to regulators input.
Its trace is actualy on the bottom side of the logic bd.
Motorola part number = 51-80942T01
Good Luck.
Satelite

Sorry, but some of the info above is incorrect and misleading.

Unswitched A+ enters the board via the 5-pin connector from the power amplifier. It runs down to the front panel connectors and leaves the board at J8/P8 pin 6, which feeds the power switch. When the front panel power switch is on, A+ is returned back to J8/P8 pin 5, which is the source of Switched A+. From here it runs under the board to two spots: into U401 which supplies the rest of the radio, and to a feedthrough hole near the rear of the board, where it gets to the Accessory connector pin 13 via an internal foil layer (the logic board is a four-layer board). Both of these paths are rather substantial foils and there is no fuse; if too much current is drawn a foil will burn out. This circuit path is plainly visible in the color circuit board X-ray views.

You could easily run a wire directly from J8/P8 pin 5 to the Accessory connector pin 13. If that foil path burnt out, something was drawing way too much current from pin 13. I couldn't readily find a current rating but I wouldn't want to draw more than 1/4 amp.

Bob M.

[Satelite]

Hello:
Certainly meant no misleading info and i apologize.
I just looked again at my schematics for the 16 pin HLN9313 bd and it says on pin 13 that its from U402-1
So that being the case then is pin 1 of U402-1 12 volts in for the regulators 5 volts out for rest of radio ?
And that pin 1 of U402 also takes off directly to logic bds pin 13 sw A+ sense output ?
If so i see where i goofed .
Satelite

[wavetar]

I couldn't readily find a current rating but I wouldn't want to draw more than 1/4 amp.

I believe you're bang on, 250ma is the rating as far as I can recall.