How to build the Hardware

GALBlast requires you to build a cheap circuit to be connected to your computer's parallel port and a 9 to 12 Volt 250mA wall mount power supply. If you have no experience in building electronics circuits, have someone build it for you.

schema.gif (right click to download 48k image file)

I have used only cheap components that have been manufactured for a long time and are second sourced. Some parts may already be laying around on your table, but the other ones should be available at your local electronics store. Many components can be replaced by similar parts. PLCC sockets may be added using a larger PCB or adaptors. Be ingenious.

Bill of Materials

IC6, C3 and SW1 are only used to support Low-voltage GALs. Replace SW1 with a jumper wire connecting the output of the 7805 to the reed relay Rel1 in case you do not want to install these parts. Do not install parts marked with * if you choose IC4b instead of IC4a.

The prices given in the last column are german marks DM without tax and are taken from http://www.elpro.org catalogue 2000, and prove that all parts together do not exceed US$ 20.

IC1

hex open collector driver

74(LS)07 or 74(LS)17

-.64

 

IC socket for IC1

DIL14

-.06

IC2

hex open collector driver

74(LS)07 or 74(LS)17

-.64

 

IC socket for IC2

DIL14

-.06

IC3

8 bit D/A converter

TLC7524 or AD7524 or MX7524

5.32

 

IC socket for IC3

DIL16

-.06

IC4a

switch mode regulator

uA78S40 or LM78S40 (or install IC4b instead)

1.50

 

IC socket for IC4a

DIL16

-.06

IC4b

CMOS op amp

CA3140E (instead of IC4a)

 

 

IC socket for IC4b

DIL8 (instead of socket for IC4a)

 

IC5

5V/1A linear voltage regulator

7805

-.35

(IC6

3.3V/0.8A linear voltage regulator

LD1117V33 or LT1086CT3.3

1.96

IC7

2.5V voltage reference diode

LM336Z2.5

1.40

D1

50V/1A silicon power diode

1N4001..1N4007

-.04

D2

40V/100mA silicon signal diode

1N4148 or 1N914

-.03

D3

40V/100mA silicon signal diode
if reed relay has no diode built in

1N4148 or 1N914

-.03

LED1

light emitting diode 10mA yellow

LED 3mm yellow

-.09

LED2

light emitting diode 10mA green

LED 3mm green

-.09

L1

storage coil 470uH / 300mA

DPU 470uH/0.5A *

1.46

C1

electrolytic capacitor

470u/35V/200mil

-.23

C2

ceramic capacitor

100n/50V/100mil

-.08

(C3

tantalum capacitor

33u/6.3V/100mil, or as specified in the data sheet of IC6)

-.41

C4

ceramic capacitor

100n/50V/100mil

-.08

C5

ceramic capacitor

100n/50V/100mil

-.08

C6

ceramic capacitor

100n/50V/100mil

-.08

C7

ceramic capacitor

100n/50V/100mil

-.08

C8

ceramic capacitor

10n/50V/100mil *

-.11

C9

electrolytic capacitor

100u/35V/100mil

-.07

C10

ceramic capacitor

4n7/50V/100mil

-.12

C11

tantalum capacitor

1u/3V/100mil

-.16

R1

resistor

1R2/0.25W 1% *

-.15

R2

resistor

180R/0.25W *

-.14

R3

resistor

220k/0.25W 1%

-.15

R4

resistor

12k/0.25W 1%

-.15

R5

resistor

4k7/0.25W

-.14

R6

resistor

100k/0.25W 1%

-.15

R7

resistor

12k/0.25W 1%

-.15

R8

resistor

390R/0.25W

-.14

R9

resistor

820R/0.25W

-.14

RN1

9 pin SIL resistor array

4k7*8

-.19

RN2

6 pin SIL resistor array

4k7*5

-.18

RN3

5 pin SIL resistor array

4k7*4

-.15

RN4

8 pin SIL resistor array

4k7*7

-.18

RN5

9 pin SIL resistor array

4k7*8

-.19

RN6

7 pin SIL resistor array

4k7*6

-.21

Rel1

DIP reed relay 5V/20mA SPST or SPDT with or without internal diode

RR1A05

1.88

(SW1

SPDT switch or 3 pin jumper posts

MS611A)

1.79 

X1

90 SubD 25 pin male connector

DMR25M

1.92

X2

DC 2.5mm power connector

HEBG25

-.37

(X3

alternate DC power connector

4 pin, do not install if X2 is used)

 

GAL1

precision IC socket

20pin

-.45

GAL2

precision IC socket

20pin

-.45

GAL3

precision IC socket

24pin 300mil

-.58

GAL4

precision IC socket

24pin 300mil

-.58

GAL5

precision IC socket

24pin 300mil

-.58

GAL6

precision IC socket

28pin 300mil

-.64

Create the double sided PCB by printing the layout file layout.gif at 300dpi, or send the layout file GALBLAS1.BRD to a PCB service of your choice (like http://www.pcb-pool.com) to have the board manufactured. If you would like to modify the schematic or layout, download the free 'light' version of the circuit layout editor Eagle 3.5 from http://www.cadsoft.de, which was used to create the files.

layout.gif (right click to download 129k image file of 300dpi resolution)

eagle.zip (download 40k Eagle circuit design files GALBLAS1.BRD and GALBLAS1.SCH)

plccadap.zip (download PLCC adaptor Eagle board file)

old.zip (download old 37k Eagle circuit files using ZN428 instead of AD/MX/TLC7524 and LM336Z2.5)

Grzegorz Krzyzanowski used an AD557 instead and had to add a 100R series resistor between the output and C10 to prevent oscillations for proper operation. Pay attention to the pinout of IC6, there are different pinouts used.

Solder all components (possible excepting IC6, C3 and SW1, which is replaced by a jumper wire) onto the PCB using sockets for all ICs, connect a wall-mount power supply delivering 9 to 12 Volt at 250mA to the DC power connector (with the positive wire on the inner connector) and measure the voltage at pin 14 of IC1 with respect to GND (pin 7 of IC1). It should read +5V. If this doesn't work, check the polarity of the power connection and the circuit.

Disconnect the power supply, insert IC4, reconnect the power supply and check if the green LED will light up. Check the switching regulator if it is not working.

There are more ways to power the GALBlast circuit than using a 9-12V voltage source and the 78S40 switching regulator. You may connect a laboratory power supply delivering +5V (@250mA) and +24V (@20mA) to X3. Install X3 and do not install R1, R2, C8, L1 in this case and replace the 78S40 (IC4a) by a CA3140E (IC4b). You may even decide to supply only +24V (@250mA) to X1 from a regulated power supply and mount a heat sink of 8K/W to IC5 (and IC6 if installed) and set the jumper wire J1. Do not install J1 in other cases, as a shortage will result. Do not try to use the +24V-only-version without a heat sink on IC5.

You may instead use an 18VAC 500mA source, a bridge rectifier, and electrolytic filter capacitor to produce +24V DC unregulated, sufficient to power GALBlast, but the best solution is a 9V AC source with bridge rectifier and electrolytic filter capacitor, which generates unregulated 12V DC @ 250mA to power the LM7805 and LD1117V33, and connect a voltage doubler (2 diodes, 2 capacitors) to produce unregulated 24V DC @ 40mA out of the 9V AC source.

If you use the 78S40 switching regulator, you may spare IC7, R7, and C8, and use a wire to connect pin 1 of IC3 to pin 8 of IC4a, reusing the reference voltage from the switching regulator for the D/A converter. You have to replace R6 with 220k to match the amplifier to the lower reference voltage.

How to build a suitable coil: Use an air gapped pot core 18/11-3H1 from Valvo or 2000N28 material pot core B65651-K0315-A028 (bobbin B65652-A0000-M001) from Siemens/Matsushita with an Al value of 315uH and wind 38 turns of 0.4 - 0.5 mm diameter magnet wire onto the bobbin. (Use 34 turns on Al 400 cores). Glue the pot core halves together and glue the coil to the board.

Disconnect power, insert the other chips, reconnect power and plug the board into your computer's parallel printer port. Launch GALBlast, select the printer port used, and try to talk to the board. The yellow LED should turn on for seconds if you issue a 'Read GAL' command, longer if you issue a 'Write GAL' command (a message box complaining about a wrong PES will appear als long as no GAL is inserted). Use the command 'Setup...' from the 'Port' menu, measure the voltage between pin 2 of any GAL socket with respect to GND on pin 10 of 20 pin sockets or pin 12 of 24 pin sockets, and enter the measured voltage to calibrate the programming voltage.

If something doesn't work, check the circuitry and the components.

If everything looks good, insert a GAL into the proper socket and try to read the contents of the GAL. The PES should be successfully read. Otherwise check the circuitry for broken traces and vias, bad solder joints, bad chips and anything else.

Ready to go

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