Quasar 3073, Manual

QUASAR PROJECT KIT # 3073 - 12/24 HOUR GIANT CLOCK

do 

NOT

 fit through the holes of X4, X5 or X6 drilled 

in 3073A PCB. The holes are meant as a placement 
guide for soldering each connector. If you are 
assemblying the kit alone use a piece of sticky tape to 
hold the male connector vertical while the short pins 
are seated in the holes. Just solder one pad and check 
the connector is vertical. Make any correction needed. 
Then solder the other pads. 

 
 
Testing.  

First check the bottom PCB, 3073B just by itself 
unconnected to 3073A. Do not put in IC’s. Plug in 
12VDC plugpack. Use a multimeter to check that there 
is +5V between both pins 4 & 14 and pin 5 of IC1. For 
IC2 there should be 5V between pins 16 & 8 and 
between pins 16 & 7. If these reading are correct, 
disconnect the power,  
 
Insert the ICs correctly orientated. Connect the two 
boards together. Apply power. The display should light 
up and show 12:00:00. The display is in 12-hour mode.  
To select the 24-hour display press the hour switch as 
you connect power.  
 
Push the two switches to see how the hour and minutes 
increase. Cover the LDR to test the dimming feature. 
Press both switches to check you can access the adjust 
mode. If you bought 4 batteries for battery backup (not 
supplied with the kit) then connect the LK1 link to 
allow the batteries to charge from the plugpack. 
 

If it does not work.

 Solder bridges and components in 

the wrong way are the most likely problems. Did you 
put in all the links? If one or more display segments are 
wrong trace back the display to the components driving 
that display segment. Look for dry-joints. 
 

Adjustment o/-255.

 If you find that you need 

an adjustment outside the range of +/-255 then this 
means that the crystal is out of specification. This can 
be fixed within limits by changing the loading 
capacitors. If the clock is running fast and the 
adjustment value needs to be more than 255 then 
increase the 27pF capacitors to 33pF (NPO type.) If it 
is running slow and needs an adjustment to be more 
than  –255 (that is,  -256,  -260 etc) then decrease the 
loading capacitors to 22pF or 18pF (NPO type.) 
 

Changes in this Kit from Original Version.

 In the 

hardware we have not allowed for two types of 2.3” 
LED display pinout. We have used the pinout our LED 
supplier makes for us (which is the variant pinout of 
the article.) Connecting the two boards together has 
been improved. In software, the author John Clarke 
kindly corrected a rollover fault so that 23:59:59 went 
to 0:00:00. 24 hour mode is the default start-up mode. 
 

Support - 

email us at: 

support@quasarelectronics.com

COMPONENTS 

Tinned copper wire 

12" 

 
Resistors 5%, 1/4W: 
10R 

R3 

1 

82R 

R11 12 14 15 16 17 18 

7 

180R 

R11 

1 

220R 

R9 10 19 20 21 22 23 

7 

470R 

R5 24 25 26 27 28 29 30 31 

9 

1K 

R7 

1 

2K2 

R2 

1 

4K7 

R4 

1 

10K 

R6 

1 

470K 

R8 

1 

Zero ohm resistors for links on 3073b 4 
2R2 1W  R1 

1 

 
0.1 104 box poly MKT      C10 

1 

1n5 box poly MKT            C9  

1 

1N4004                  

D1 2 3 4 

4 

1N4148                  

D5 D6 

2 

4.000MHZ                         Xtal 

1 

10uF/25V mini 

C1 2 3 4 6  

5 

100uF/16V mini 

C5 

1 

15V 1W zener diode 

ZD1 

1 

27p ceramic NPO type    C7 C8 

2 

LDR                     

LDR 

1 

BC328                   

Q1 – Q8 

8 

4051                    

IC2 

1 

PIC16F84                

IC1 

1 

ULN2003A                

IC3 

1 

7905                    

IC4 

1 

20 pin IC socket        

1 

18 pin IC socket        

1 

16 pin IC socket        

2 

0.05” Metal Pins 

8 

3mm x 6mm nut and bolt set                                1 set 
Metal spacer 3mm x 15mm 

4 

3mm screws x 6mm 

8 

2 pin SIL header 

1 

jumper 

1 

LED 0.56" display 

2 

LED 2.3" display 

4 

8 pin female header 

3 

8 pin male SIL strip 

3 

3073A PCB 1 
3073B PCB 1