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MaxTrac Logic Board Jumpers And Connectors By Robert W. Meister WA1MIK

The MaxTrac and Radius mobile radios contain a microprocessor-controlled logic board that determines the features, operating modes, and accessories. The main difference is the number of pins on the accessory connector: 5 or 16. Most owners prefer radios with 16-pin accessory connectors.

Logic Board Jumpers:

Each logic board contains one or three jumpers that the user can configure. These are similar in function to those found in a GM300, although the GM300 has additional jumpers. (See the companion GM300 article here.) Each jumper consists of a three-pin header with a jumper plug that can be positioned to connect the center pin to either outside pin. The jumper plugs are usually black plastic, although other colors are also available.

Here's a 5-pin board, HLN5172, with its one jumper (JU601) circled. Note that only the positions (A or B) are silk-screened on the boards with only one jumper. The location of this jumper may vary on other 5-pin boards.

Here's a masked 5-pin board, HLN9123, for comparison:

Here's a 16-pin board, HLN9313, with all three of its jumpers circled. All the jumper designations, as well as their positions, are silk-screened on the 16-pin boards:

Some boards may label these jumpers P551, P601, or P608. They are the same as the JU numbers shown below. All 5-pin logic boards have one jumper, JU601. Such boards are HLN5172, HLN5173, and HLN9123. Any of these models can have an A or B suffix. There may be additional board numbers for Radius radios.

All 16-pin logic boards have three jumpers, JU551, JU601, and JU808. The MaxTrac manuals document two boards: the HLN9313 for the VHF/UHF/800 MHz radios, and the FRN5529 for the 900 MHz MaxTrac only. Any of these models can have an A or B suffix. There may be additional board numbers for Radius radios.

The following table describes the functions and the default position of each jumper. The default position is indicated by the number of accessory jack pins (5 or 16) shown within parentheses.

Jumper	Position	Function
JU551	A	RX Audio on pin 11 not muted, not de-emphasized
	B (5,16)	RX Audio on pin 11 muted and de-emphasized
JU601	A (16)	RX High-Speed Data after 300 Hz high-pass filter
	B (5)	RX High-Speed Data before 300 Hz high-pass filter
JU808	A (5,16)	ACC jack pin 12 is programmable input/output
	B	ACC jack pin 12 used for SCI programming

The default position for JU601 depends on the logic board in use. On 5-pin logic boards, position "B" is the default. On 16-pin logic boards, position "A" is the default. This jumper would only be used for applications where the receiver is expecting high-speed data that the microprocessor must decode. Position "B" lets signals below 300 Hz get through; position "A" removes low-frequency signals. For amateur use, the jumper position is unimportant; you can set it to position "A" if it makes you happier.

Ignition Control Jumper:

This jumper is removed when you wish to use ignition control on your radio. Without it, you will need to supply nominal 12V to both the main DC plug as well as the proper pin on the accessory plug, to allow the radio to turn on and operate. These pins are described in detail in another article in the MaxTrac section of this web site.

The ignition control jumper is indicated on each of the photos above. On the 5-pin logic boards it's a piece of insulated wire or a zero-ohm jumper - a piece of wire that looks like a 1/4-watt resistor but has only one black band centered on a white or tan body. On the 16-pin logic boards, it's a small green 2A fuse that sits between some other 1/4-watt resistors. The schematics refer to it as F801 on some drawings or JU801 on others. If your radio has a blown ignition fuse, it can be replaced with a low-value (1-3 ohm) resistor.

Logic Board Connectors:

The MaxTrac logic boards have three major connectors on them: