See the Cables section for information on the 22 pin control head connectors. The pin number locater for the 22 pin connector is exactly the same for all the 22 pin control head connectors as viewed from the rear of the control head. You may find useful information through out this page, so do not limit your reading to a specific example if you are going to make one of these modifications.
All of the modifications pictured on this page are shown as being connected to "Gray Connector Pin 21 Mode Strobe". This connection is only used when System 90*s accessories that use the mode lines are installed (i.e. System 90*s boards with Indicators or Display, operator select non-priority scan or operator select PL/DPL boards, etc.). The "Mode Strobe" signal is provided by the System 90*s accessory. If none of these accessories are installed there is no "Mode Strobe" signal and any lines shown connected to this signal are connected to ground instead. For example: "Black Connector Pin 21 Audio Shield" is commonly used as the ground on clamshell control heads. If you do not have any of these System 90*s accessories, please substitute a suitable ground connection in place of the "Gray Connector Pin 21 Mode Strobe" connection. Always keep in mind, if you add any of these System 90*s accessories at a later date you must change this ground connection back to the "Gray Connector Pin 21 Mode Strobe" connection. If you use a clamshell control head please check to see if it uses ground or Mode Strobe.
The diodes used in these modifications have two purposes. Some are only used to electronically disconnect the Mode Select control head from the mode lines in the radio's cable. Others are used to encode the binary code used by the radio in addition to providing the disconnect. If you do not have any System 90*s accessories installed that use the mode lines, only the diodes that provide the disconnect (not the encoding diodes) may be replaced with a wire. It does not hurt to have the diodes anyway, as it makes the control head fully compatible with all Syntor X radios so their use is definitely recommended. All the diodes shown for these conversions are very inexpensive, common, so called "small signal", silicon diodes.
When adding a wire to an already wired connector pin, the following technique has been used successfully. Check out the clearances with a dry run before starting (i.e. strip the new wire end and poke it into the connector body with the pin you want to add it to). Use the contact removal tool to remove the pin, use a soldering setup to tin the wire end then very carefully tack solder a small gage wire to the pin. Try and position the wire over the crimp and pay attention to clearances with the connector body. Be careful not to get any solder near the pin contact or the part that snaps into the connector housing and locks it into place. Use the minimum amount of solder needed to make a good connection, too much solder or solder flowing into the wrong place will make it impossible to get the pin back into the connector body. Carefully reinstall the pin in the connector housing. Motorola never intended this to be done, just look at how much trouble they went to to make sure the System 90*s connectors had two pins for the same signal so they could be daisy chained. This technique might not be as sturdy, but it does work. Also do not forget to check the cable wiring first, the pin you want to use may already have a daisy chained connection to an unused connector position.
Syntor Clamshell control head conversion to Syntor X:
If you have a Syntor clamshell control head with a 16 mode rotary switch, regardless of the total number of modes the control head selects, and you put it on a Syntor X radio, the mode selector will be off by one position. This means the Syntor clamshell on a Syntor X radio will select mode 1 when the selector displays 16, mode 2 when it displays 1, mode 3 when it displays 2, etc. This is because the white plastic disc inside the clamshell is different on the Syntor X. Here are the Motorola part numbers for the disc:
36-80148B01 - Syntor $ 7.50
36-80148B02 - Syntor X $ 7.95
The Syntor X disc is keyed differently so the modes selected by the 16 position switch match the number it displays. To fix this problem all you have to do is get the Syntor X 36-80148B02 disc, take the Syntor clamshell apart, swap the new disc for the old one and put it back together. If you are really good at working with plastics I suppose you could reshape the D shaped hole in the center of the Syntor disc to duplicate the Syntor X orientation instead of getting a replacement disc.
The Syntor clamshell control head will still be missing special isolation diodes required by some Syntor X control heads and accessories (see below). Also, all of the 8 mode lines (modes 1 through 8) not used by the 16 position switch (this switch uses mode lines 1, 2, 3 and 4) or the A/B or R/D switch (this switch uses mode line 5) must be pulled to ground (using diodes is best for full compatibility). If there is an A/B or R/D switch it will be wired backwards (i.e. B/A or D/R). Lastly, the 22 pin blue connector pins 10 and 6 (mode 11 and 12) are shorted to ground inside the clamshell and should be disconnected (i.e. left open). The 22 pin blue connector pins 8 and 19 (mode 9 and 10) are already disconnected, exactly as they should be.
If you add the isolation diodes and perform the above steps, the Syntor clamshell control head will be transformed into a complete Syntor X clamshell control head. If you do everything except the isolation diodes it will only work with Syntor X radios that do not have the "Mode Strobe" signal.
There are other conversions possible with these clamshell control heads, like adding an A/B switch, adding a scan enable switch, or adding a 64 mode switch (use the ground wire or diode you installed on mode line 6 as diode CR4 in the 64 mode instructions).
16 mode to 32 mode Clamshell control head conversion:
The example cable wiring pin out for a clamshell control head should be referred to for the following 16 mode clamshell control head 32 mode conversion. Keep in mind the clamshell control heads have internal connection posts from the 22 pin black and blue connectors. Wires can be connected inside the control head and snuck outside the case if you want an alternative to splicing into a pin on an external 22 pin connector (for externally mounted modifications). Depending on how you mount external switches, having them attached directly to the cable can be a nuisance when the cable is removed. Keep a strategy in mind to allow easy separation of the cable and control heads (you may need extra in-line mating connectors). Try to avoid having the control head(s) and cable being hopelessly entangled. If it's easy to unmount the external modification then having it attached to the cable is not so bad. The PL/DPL hangup box is an example of an accessory that is attached to the cable, but mounted on the vehicle. It is easy to unmount so it's not a problem.
The following schematic is for the conversion of the 16 mode clamshell control head HCN1019A and System 90*s accessory (for example the HLN4290A 8 mode operator select non-priority scan control head) into a 32 mode clamshell control head. This example is for an externally connected and mounted switch. The gray connector pin 21 (Mode Strobe) must not be disconnected from the clamshell black connector pin 5, it must be shared. The gray connector pin 21 (Mode Strobe) should be connected to the common of the new switch. The lt. purple connector pin 14 (Mode 5) should already be connected to the blue connector pin 4 (Mode 5). The blue connector pin 4 (mode 5) should be disconnected and then connected to the anode of the diode.
If you want to mount the switch inside the 16 mode clamshell control head (photo and closeup), first double check the anode of diode CR0003 (from the HLN4330A diode matrix board) goes to the blue connector pin 4 (Mode 5) and the cathode goes to the RED wire. Disconnect the RED wire from the clamshell control head mode switch or circuit board (leave the RED wire HLN4330A diode matrix board end alone) and reconnected it to the A position of the new switch (the wire will need a splice or replacement to lengthen it). The new switch common should be connected to the same place the RED wire was disconnected from. If you have to splice anyway the red wire can be cut in half and each end spliced. The RED wire can also be replaced by 2 new wires. The factory switch mounts on the top cover of the clamshell housing, on the nearly vertical front between the volume and power switch, near the illuminated volume escutcheon. The wires for the new switch will need to be long enough to disassemble the two halves of the clamshell housing. Where ever you mount your switch always keep clearances with obstructions in mind. This modification will work with or without any System 90*s accessories. Use the radio manual for documentation as the above wiring example will not be of any use. As long as I could make a clean looking installation with the new switch, this would be my first choice (simply my personal preference).
You can also use the internal switch wiring (above), sneak the wires out of the clamshell housing and mount the switch externally. This would make sense if the external switch mounting was attached to the clamshell housing. It has the advantage of working with or without System 90*s accessories and you would not need to find a diode to use either. Even though the wiring would be a bit uglier, this way would be my choice if I could not do a clean looking internal switch mounting. If there are no System 90*s accessories with a PRI scan switch I would also add a second external switch connected to J1-31 Channel Scan Enable and ground (i.e. black connector pin 21, Audio Shield) for scan enable.
If you want to mount the switch and connect the wiring externally, but you do not have any System 90*s accessories, either sneak the wires out (as above) or replace the "gray connector pin 21 Mode Strobe" label with "black connector pin 21 Audio Shield" and replace the "lt. purple connector pin 14 mode 5" label with "radio connector J1 pin 12 (white-black wire) mode 5". The black connector pin 21 (Audio Shield) must not be disconnected from the clamshell black connector, it must be shared. The black connector pin 21 (Audio Shield) should be connected to the common of the new switch. The blue connector pin 4 (Mode 5) which should be connected to the "radio connector J1 pin 12 (white-black wire) mode 5", should be disconnected and then connected to the anode of the diode. If you add any System 90*s accessories at a latter date, remember to rewire this switch (this rewiring is a disadvantage that makes sneaking the wires out much more attractive because they will not need rewiring if you remember to wire the new switch common directly to the mode switch common). Use the radio manual and the above wiring example for documentation, as the above wiring example alone will not be very helpful.
As long as you maintain the signal path integrity (regardless of how it's actually hooked up) in the schematics below you can modify these control heads any way you want. Keep in mind where you connect wires and where you mount the things connected to those wires can be important during assembly, disassembly or maintenance.
Other Clamshell control head conversions:
I believe 8 mode HCN1009A clamshell control head does not use a binary coded switch, instead it selects one of the 8 mode lines. The switch is originally hooked up with each switch position wired to the same numbered mode lines on the 22 pin blue connector (see the radio service manual for schematic). This control head is missing the diodes needed to make it compatible with System 90*s accessories that use the mode lines. In order to convert this control head to use more than 8 modes, a diode matrix must be used to convert the 1 of 8 switch selection into a 3 bit binary code (M1, M2 and M3) with mode lines M4, M5, M6, M7 and M8 pulled down. Below is a conversion that uses 17 diodes and rewires the switch. This conversion will make the 8 mode clamshell control head fully Syntor X compatible and make it possible to convert it into a 32 mode head.
The converted HCN1009A clamshell control head can now be made into a useful 32 mode control head using the external four position switch (shown below) used to replace the Mode 4 and Mode 5 lines (with different 22 pin connector wiring for the clamshell, i.e. there is no lt. purple connector). The radio service manual has the best documentation to help you figure this out.
Once you solve the missing diodes problem you can convert old Syntor clamshell control heads into Syntor X control heads (see above) and expand the availability of control heads for the Syntor X radios. The control heads with binary encoded mode switches are the easiest to convert (you do not need a binary encoding diode matrix like the 8 mode conversion example above). The HCN1015A 16 mode with Talkaround (32 modes total) is absolutely the easiest conversion (it's already a 32 mode head) and is well worth doing. Remember all 8 mode lines must be diode isolated to be fully Syntor X compatible.
The 8 mode with Talkaround (16 modes total) HCN1023A could also be converted to 32 modes with a four position switch (with different 22 pin connector wiring for the clamshell, i.e. there is no lt. purple connector) if the "R - D" toggle switch is disconnected from the mode lines. The wires that are disconnected from the switch would be connected together and have the splice insulated (i.e. electrical tape of heat shrink tubing). You can now connect this toggle switch to J1-31 Channel Scan Enable and ground. Then you would have a built in scan switch with a new external four position bank select switch.
System 90*s alternate control head 32 mode conversions:
The example cable wiring pin out for a System 90*s alternate control head should be referred to for the following 8 / 16 mode to 32 mode System 90*s alternate control head conversion. Unlike the clamshell control heads, these boards do not have internal posts for the 22 pin connectors and it is really difficult to "sneak" wires out of this housing, so internal connections to the boards are not a good way to proceed.
The following schematic is for the conversion of a 8 or 16 mode System 90*s alternate control head into a 32 mode control head. This example is for an externally mounted 4 position 2 wafer switch. Depending on your exact setup many or all of the wires needed may be found on the 6 pin connector to the right of the microphone and speaker connectors. The gray and lt. purple connector pins listed are the source of the wires on the 6 pin connector. The 6 pin connector pins 1 (mode 4), 3 (Mode 5) and 4 (Mode Strobe) will be disconnected if they are already present and these wires will be used to connect the new switch. Any bank switches (A, A/B or Repeat/Direct) on the System 90*s control head will be disabled by this conversion and no longer function, except to turn on power to the radio. You may have to make cables for the gray and lt. purple connectors or scrounge wires with pins you can use. Just disconnect the indicated wires, provide any wires needed that were not present on the 6 pin connector and hook them up as indicated in the schematic. Please read through the page's beginning paragraphs above for more information on the connectors, pins and techniques. In addition to these changes there are jumpers on the 8 mode select board (the top board in the housing) that must be changed to accommodate 32 modes.
Here is another circuit to accomplish the same conversion with a 4 position single wafer switch that used 2 additional diodes. Other than these differences the conversion is exactly the same as the one above. If you want to add lights and wire them to the new switch you could use this conversion with the 4 position 2 wafer switch and use the second switch wafer to switch the bank select lights on. In this case you would also need to provide power for the lights.
System 90*s 32 mode jumpering:
HLN4336A (16/32 Mode Select with Scan and Display board) 32 mode jumpering: set JU9 (black wire) and JU10 (brown wire) to their B positions.
*TRN4338A (8 Mode Select with Scan and Indicators board) 32 mode jumpering: set JU7 (black wire) and JU8 (brown wire) to their B positions. Move jumper JU11 (orange wire) to the JU7 position A.
TRN4344A (8 Mode Select board, non-scanning) 32 mode jumpering: set JU8 (black wire) and JU9 (brown wire) to their B positions.
The real meaning of "Scan" on the above mode select boards is simply a switch (labeled "PRI") to ground J1-31 (Channel Scan Enable) and activate the radios built in scanning ability.
This section does not apply to System 90*s control heads that already have the "PRI" scan enable switch.
Having a scan enable switch involves having J1-31 (Channel Scan Enable) brought up to the control head and having Personality Board jumper JU1 removed. If you do not already have a J1-31 wire in your cable to use for the scan switch, you can commandeer another cable wire or add a new one. To do this you will have to open the J1 connector housing. To add a wire you need a contact pin attached to a suitable gauge of wire (20-24 gauge). The contact pin is placed into the J1-31 position and the wire is routed outside the housing with the main cable. This wire will not go inside the existing cable jacket and must be run on the outside. To commandeer another cable wire, find an unused wire or one that can be freed up and move its contact pin to the J1-31 connector position. There are things you can do to free up a wire. For example, if your control heads uses Display Enable you can install Personality Board jumper JU14 (Display Enable) then move the Display enable wire from J1-33 to J1-31 (remember to disconnect the other end of the wire from the control head connector). The jumper JU14 will take over enabling the Display Enable function which allows you to commandeer its old wire. If your radio does not use Display Enable then this wire is already free to commandeer.
Any System 90*s control head head that does not have a scan enable switch (labeled "PRI") can add an external switch. All the switch has to do is ground J1-31 (Channel Scan Enable) and activate the radios built in scanning ability. You will need a switch housing and a place to mount it. The control heads with the built in "PRI" scan enable switch have a fancy display light that tells you when a primary or secondary priority scan mode is active that this switch will not have. Still being able to control the scan is a big advantage.
Any Clamshell control head can have the scan switch added internally or externally. For an external switch you can just run this wire to a switch, connect a ground to the other side of the switch, find a switch housing and place to mount it. For an internal switch you need to find an unused pin on the clamshell control head that is not currently connected inside the clamshell (mode lines 9 through 12 on the 22 pin blue connector are not used), plug in a contact pin with the J1-31 wire on it (you may have to remove an existing contact pin first) and use it to wire to the switch. Here is a photo of an internal scan switch from the outside (clamshell inside photo to be added). The new scan switch is visible just to the right of the "Squelch" escutcheon.
The scan enable switch only enables the scan. The EEPROM must also be programmed for scanning. If the EEPROM is not programmed correctly, using the scan enable switch will not have any effect.
Older Motorola radio lines (including the Syntor) had complicated scan control heads that had to make the radio scan because it did not have any built in scanning ability. These older scan control heads are not compatible with Syntor X radios.
There are on-line parts sources like http://www.fix.net/~jparker/dans.html , http://www.digikey.com/ , http://www.jameco.com/ , http://www.mouser.com/ , http://www.newark.com/ . You may also have local electronic stores, even Radio Shack may have parts you can use. These are only examples of where to find parts. Around here, a local electronics store called Norvac had a CG Electronics brand 4 position 3 wafer switch for about $ 5 new and a neat little black plastic box (actually, it was physically a single wafer with all three 4 position switches on a single wafer).
Take a moment to look at the above examples and you will notice there is nothing complicated about these modifications. The hard part is figuring where and how to hook them up to the radio's cable and control heads.
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