May 28, 2023
HAL Communications MKB-1 Morse Keyboard and HAL ID1 Kit.
I purchased this keyboard at the Charlotte Hamfest. It did not work when I tested it. I could not find
information about it so I wrote to Motorola Solutions. They own HAL now. After a few days, they sent
me an instruction manual. The manual has the theory of operation and a schematic.
I tried to find out why my keyboard did not work. I measured the voltages in the circuit board and they
are all correct. After a while, I found that if I temporarily ground the gate of the 2N5062 SCR, the
keyboard would work. The SCR powers up disabled when it should be enabled.
In the theory of operation, there is an error on the bottom of page 5 and the top of page 6. It says
“…….the SCR to fire and a current pulse to flow…….”. The SCR does not fire to generate a pulse. The SCR
has to be on when the keyboard is waiting for a key to be pushed. While it is on, there is 5.3 volts on the
wires to the keyboard. When a key is pushed, one of the wires is grounded causing current to flow in the
toroid cores. Immediately the SCR is turned off disabling any additional keyboard input. After the Morse
character is sent, the SCR is enabled. This provides 5.3 volts to the keyboard and be ready for the next
character.
In my keyboard, I am unable to find out why the SCR is powering up in the disabled state. The only
memory in the keyboard are the four 7474 flip-flops. They are all correct after power up.
There is a wire from the gate of the SCR to a key on the bottom left of the keyboard. That key is not
marked. When it is pushed the gate of the SCR is temporarily grounded. After that the keyboard works.
On the schematic, the wire is marked KB-ID Clear. When this key is pushed after power on, “H2MYG” is
sent. It must have something to do with the KB-ID1. I labeled it “Reset”.
This keyboard has an optional HAL KB-ID1 circuit board. When the “Here Is” key is pressed, it sends DE
followed by a call sign. If the “Here Is” key is released before the call sign starts, only DE is sent. The key
has to be held down until the call sign starts for the call to be sent. When the key is used “DE K2MYG” is
sent. The unmarked key above the CQ key sends 73 when pushed.
The Weight control was way out of range. It had to be set at the extreme end of its rotation for the
characters to be close to correct. Therefore, I disabled it by connecting a 56-ohm resistor in place of it.
Now when a five is sent, the dot length is the same as the space between each dot.
The output transistor 2N5655 can handle 250 volts at 0.5 amps.
The range of the speed control is six to 53 wpm.
73 Tom N4TL
In the combined PDF, Page 1 is this page.
Pages 2 to 41 are the HAL MKB-1 Instruction manual.
Pages 42 to 62 are the HAL ID1 Kit instructions.
Summary of Contents for MKB-1
Page 2: ...ffiffi HfiL sMrilUNlWl N HH URBANA ILLINOIS 61801 0 H fiF U TI NQ UIPMENT...
Page 37: ...33...
Page 38: ...34...
Page 39: ...35...
Page 40: ...l ff r lr s t J l t JhN R l nill r et rrs sFtp 36...
Page 60: ...o EG O O s o oT OH T o 3 E E oo g t E t E E g o o Y A I D Y A crr ir...
