Joined: May 15, Messages: 1 Likes Received: 0. Captain Kilowatt Professional Amateur. Joined: Apr 6, Messages: 16, Likes Received: 10, Joined: Aug 18, Messages: 9 Likes Received: 0. Joined: Apr 18, Messages: 5, Likes Received: RonF New Member. Joined: Aug 14, Messages: 2 Likes Received: 0. Barry Cubio Member. Joined: Mar 9, Messages: 1 Likes Received: 0. You can make your own or just search on Ebay for "GM programming" or make programming interface from below "at your own risk".
GM programming connection When looking at the radio here are the numbers. You will need to access the logic board on the underside of the radio.
Remove the front of radio and the bottom cover and lift off the RF shield. See photo below. If you use thin wire you will be able to feed this out the edge of the 16 way connector. This 12V nominal signal runs through a fuse F on the logic board.
Its location depends on whether you have a masked logic board or an enhanced logic board. This fuse supplies 12V to the Ignition Control pin of the Accessory connector. If 12V is present on that pin, the radio will turn on via the front-panel power switch.
If this fuse is blown or removed, you must supply your own 12V to the Ignition Control pin of the Accessory connector to get the radio to turn on. To enable external Ignition Control you need to blow or remove F and supply your own possibly switched 12V supply to that pin on the Accessory connector. Nothing in any software package will disable Ignition Control. It's all done in hardware.
This reduces the gain of the receiver and improves intermod rejection by 10dB. The circuit can be activated by soldering a small jumper on the RF board. The GM control head is quite similar to the MaxTrac. There is an additional circuit board, soldered to the logic board pins, that the control head connectors plug into, that provides some RF filtering and Zener diodes to protect from excessive voltage. Also, the internal speaker now connects through the control head cables, rather than on its own two-wire cable.
This makes it easier to remote-mount a GM There are kits available for this purpose. For comparison, here's the inside view of a MaxTrac. Notice the lack of shielding and no filter board between the logic board and control head. The GM logic board is significantly different from the MaxTrac logic board. The audio power amplifier is one single IC rather than discrete transistors. The heat-sink is considerably different and mounts only to the bottom of the chassis - no more T8 flat-head screws through the side of the chassis.
There are far fewer components on the board too. All GM logic boards have a pin accessory connector. A full metal shield covers the entire logic board, just like they have for the RF board; the MaxTrac only shields the microprocessor area.
This further reduces spurious emissions. The GM audio amplifier drives both sides of the loudspeaker. Therefore you must NOT ground either pin 1 or pin 16 of the accessory connector. You must run two wires to an external speaker. The same circuit design and components are used on the Spectra radios and they suffer from the same restriction.
Grounding either speaker lead may let out the chip's lifetime supply of smoke, even though the manufacturer claims the ICs are short-circuit-proof.
All of these are No Longer Available through Motorola, but can be found on popular auction sites. The GM RF power amplifier has a thermistor mounted near the final transistor, so it actually senses the heat-sink temperature.
This makes GM radios more suitable for repeater transmitter usage. They still need adequate forced-air cooling. This extra signal requires a 6-wire cable and connector between the PA and the logic board the MaxTracs only have a 5-wire cable and connector.
I have heard that you can use a GM PA in a MaxTrac by snipping the temperature sensor wire off the connector, but I personally would not butcher either the radio or the cable that way. You can fool RSS into thinking the radio is blank by manually erasing the serial number filling it with spaces and entering a few more bytes using the bit-banging facility available in the MaxTrac lab RSS program.
After that, you should be able to initialize the radio using the GM RSS or write a previously saved code plug to the radio. Initialization is exactly the same as the steps you'd do for a MaxTrac: set the radio model number, frequency range, signaling features, panel number, serial number, key in the crystal data and 9.
To blank the radio, you need to deposit the following data at the locations shown. These values came directly from a factory-fresh blank board. This data will go directly into the radio's memory.
You may want to write down the contents of these locations first, incase something goes terribly wrong. Use this at your own risk. All values are hexadecimal. B60E FF??? B60F 4F??? B FF??? After setting the memory to these values, the radio will appear blanked to the GM RSS, and you'll have to go through the blank board replacement procedure and either align the radio, or fill in the various fields with data that was previously there. You can also write any previously saved code plug to the radio, but make sure you use one that matches the band and number of modes.
During the first screen of the initialization procedure, you'll need to select the frequency range. Go through the entire list using the up-arrow, then go through it a second time to find the exact range.
Once the correct range is chosen, you'll have no problem choosing a model number.
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