Subject: Icom Z1A mods
[B]+[#]+[POWER] = Extended Receive.
VFO *DISPLAYS* 50-299.900 and 300-999.900.
AM Aircraft band enabled.
SET mode now has a new "PLACE" function for setting the direct entry starting digit.
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There is room for four diodes in the Z1A located on the CPU board to the left of the ribbon cable connector.
On a US version, only the bottom two are installed.
D15 is just below and to the right of the four diodes.
These diodes are bigger than the rest of the surface mounted components and are easy to spot.
+-+ +-+
| | | | <---- Installing diodes in either of these seems to do
+-+ +-+ nothing.
+-+ +-+
| | | | <---- IN:US Version 144-148 TX 440-450 TX
+-+ +-+ OUT:Extended 136-174 TX 380-470 TX (Lose auto-repeater
^ and tone encode)
|
+------------ IN:US 144-148 TX 440-450 TX
OUT:European 144-148 TX 430-440 TX
+-+
"D15"--> | | <---- IN:US Version Stock
+-+ OUT:Extended TX 136-174 380-470 (keeps auto-repeater
and tone encode)
A word of warning about messing with the four diode pads:
If you detach either one of the installed diodes, the CPU will reset and you'll lose ALL of your memories.
found that out the hard way...
D15 doesn't seem to affect the memories at all.
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Z1A 800MHz receive.
Install two transistors.
Part #UN9110 can be ordered from ICOM Service Department.
This mod is not for the non-technical person.
The radio pretty much has to be completely disassembled to get to the pads.
01) Remove the control head and battery.
02) Remove the 4 back screws and 4 battery compartment screws.
03) Separate the case.
04) Locate the circuit board with the two channel select/squelch knobs.
This is the board we're looking for. Unfortunately, it's on the back.
05) CAREFULLY remove the wide ribbon cable that connects the upper and lower circuit boards.
06) LOOSEN the three screws on the LOWER circuit board.
07) Remove the two screws on the back of the radio, on the top of the battery compartment.
08) Remove the three screws on the battery contacts.
09) Slide the RF assembly up and it should separate from the rest of the radio.
10) Remove the knobs and carefully remove the ring nuts from the case.
11) Remove the metal bracket that is between the case and the pots.
12) CAREFULLY Desolder the grounding tab on the left side of the circuit board.
13) Remove the two screws holding the board down.
14) The board should now be free. Carefully wiggle and pull and pry until the board is released.
You may have to partially or fully remove the battery spring mechanism.
15) Flip the board over. There is a large multi-pin jack on the back, slightly high and centered.
Look for two empty, 3 pin pads right next to it.
16) Carefully solder the two transistors onto the pads.
17) Check your connections. You do NOT want to have to disassemble this twice.
18) Check them again.
19) Reassemble the radio in reverse order. Remember to resolder the grounding tab.
20) Turn it on. Select UHF, key in an 800MHz frequency and listen. There is no need to reset the VFO or memories.
Diagram:
This is a close up view of the area to look for.
# = 3 pin part, diode/transistor
|| and == = 2 pin SMD diode/resistor
(*) = 3 pin surface mounted transistor.
(*) (*) || || # #
|| || || ||
#
+----------------------------+
| MULTI-PIN JACK |
+----------------------------+
== == || ||
kind of hard to draw in ascii.
This diagram needs a non-proportional font to look right...
You do NOT have to do a [B]+[#]+POWER to reset once completed.
After this mod, mine receives well into the 900MHz band.
Bruce KD6ALI
baptpdc
