GW6BWX Low Cost Testcard Generator
Inside this box is the GW6BWX Low Cost Testcard Generator. On the front of the box is, from top to bottom, Video out, page selector, on/off switch and power. It fits inside a box designed for remote controls, this has a battery compartment that will allow the use of a 9V PP3 for portable operations.
The Test Card Generator was first discribed in CQTV201 by Brian, GW6BWX. He took the discrete logic design of the Cropredy Test Card Generator and put it into a CPLD programmable logic chip. He also found space for the PAL encoder. This gives a very compact design. My PCB for the design is only 2.6 by 1.8 inches. I've built the Mark2 version which was published in CQTV205.
Please take a look at Brian's website www.atv-projects.com for the background on this project and other ATV related projects.
Circuit Diagram
My circuit diagram is very similar to Brian's original circuit diagram. The main difference are the two oscillators. I have used "tiny logic" inverters to form an oscillator. My circuit includes a 7805 +5V regulator so the board can be run off a standard 12V supply.
| Qty | Value | Package | Parts |
| 7 | 2k2 | 0603 | R1, R4, R11, R24, R25, R26, R27 |
| 2 | 1k | 0603 | R2, R5 |
| 1 | 3k9 | 0603 | R6 |
| 1 | 1k5 | 0603 | R7 |
| 6 | 1k2 | 0603 | R8, R14, R18, R23, R28, R30 |
| 1 | 820 | 0603 | R9 |
| 1 | 680 | 0603 | R10 |
| 2 | 470 | 0603 | R12, R22 |
| 1 | 3k3 | 0603 | R13 |
| 2 | 10k | 0603 | R15, R16 |
| 1 | 68 | 0603 | R20 |
| 1 | 75 | 0603 | R21 |
| 2 | 15k | 0603 | R29, R31 |
| 1 | 39p | 0603 | C5 |
| 1 | 330p | 0603 | C6 |
| 8 | 100n | 0603 | C7, C10, C11, C13, C14, C15, C16, C17 |
| 1 | 470u | C9 | |
| 1 | 1u | C12 | |
| 4 | 22p | 0603 | C18, C19, C20, C21 |
| 1 | 33u | 1812 | L1 |
| 1 | 17.73447MHz | HC49/S | XL1 |
| 1 | 16MHz | HC49/S | XL2 |
| 1 | 27C512AP | DIP28 | IC1 |
| 1 | M4A5-64/32 | PLCC44 | IC3 |
| 1 | 7805 | TO220 | IC4 |
| 2 | 1G04 | SOT23-5 | IC5, IC6 |
| 1 | BC848 | BC848 | T1 |
| 1 | BCX71 | BCX71SMD | T2 |
| 2 | Header 2x1 | JP1, JP2 | |
| 1 | Header 5x1 | JP3 |
Construction
The test card generator was built on double sided PCB. One side is plain copper and is used as the main ground. Through hole components are mounted on this side. All surface mount components are mounted on the track side of the PCB. The artwork should be printed out at 300dpi. The outer dimensions should be 2.6 by 1.8 inches, plus or minus a little bit. Placement diagrams for the top and bottom show where the components should be mounted.
Programming
When the unit is all built up it is time to program the CPLD. Using a small
JTAG adapter connected to the parallel port and the Lattice download program it is
a 5 second job. I built the JTAG adapter myself. You can find details on the
web, I will put details of my version on this site when time allows. Then
it's just a case of designing the testcards you want in
the EPROM. Brian has a PC program to help develop the test cards. See his
test card
page for more info on this.
Acknowledgements
I would like to thank Brian for all the hard work and effort that has gone
into this project. The picture on page 31 in CQTV202 shows his original test
setup for the test card generator. It's a long way from the design he shows
on his web site. Please take a look at his web site
www.atv-projects.com.
Just a quick disclaimer, if you fry something even if my design is wrong it is your problem! I have tried to make these details as accurate as possible but I accept no responsibility for any errors or omissions. There is no technical support for any of my projects.