The Commodore C64 was already a great machine in its day in terms of graphic capabilities. However, the 40 characters were not enough for office applications such as word processing or terminal programmes.
There were software solutions that halved the resolution of a single character and could thus display 80 characters, but the quality was not really good. Maybe acceptable for a first impression of a text, but not suitable for real work.
So external extensions from various manufacturers came onto the market quite quickly. These brought their own graphics chip and could thus display 80 characters. However, a monitor with a composite input was required. The TV sets that were popular at the time were not suitable for this and at that time only very rarely had the corresponding input.
In addition, these cards were not exactly cheap. On average, such a card cost around $200. And all these cards were incompatible with the standard programs of the C64, which required corresponding extra software. And such a word processing program cost an extra $100. So it was not a cheap pleasure.
But in order to be able to use the C64 more professionally, there was no getting around such an expansion card for the expansion port of the C64.
One of these representatives is the B.I.-80 Display Adapter from the company Batteries Included. This card even came with a case. This card had the special feature that not only the video signal of the C64 could be looped through, but with the included adapter the Y/C (S-Video or sometimes called S-VHS) signal could be used.
So this expansion card has pretty much the best display quality as far as the 80 character cards were concerned. And you could switch between 40 and 80 characters by SYS command without having to change a cable or change the input on the monitor.
That was quite practical and made the work much easier. The card is based on the well known 6545 chip from Motorola.
Since these cards are hard to find on the second hand market today, it is time to preserve this old hardware by rebuilding it.
First of all, a corresponding circuit diagram is needed. Since this was not to be found in the Internet, the whole must be provided by backward search with the help of the old equipped circuit board.
I make it a bit easier for myself and remove all components in advance. This is faster for me than measuring and tracing the wires. A board in the size costs well one to two days of work, in order to trace by hand all the lines, or to look for lines below ICs.
With the right equipment, it doesn’t take me 2 hours to gently remove all the components from the board without damaging anything. After all, I want to reassemble the board later. And then it should work again.
So the first step is to remove all components. Of course I have to take pictures before, so that I can assign the components to their positions later.
When all parts are removed, I put both sides of the board on a scanner and take pictures. A flatbed scanner has the advantage that the board is captured without distortions. With a camera (especially bad if it’s a smartphone camera) you can only get really very good results with a lot of effort.
And since you need both sides to be congruent, you would otherwise have to work this out with a lot of manual labor using an image editing program.
Any cheap flatbed scanner will do it faster and easier. After that you have two wonderful pictures from both sides:
The easy part is done. But now you need something that a computer can process. With the appropriate PCB software, you read these two pages, bring them over each other (so that all holes are exactly on top of each other) and trace the traces. The result is a finished Gerber file.
With this you could already have circuit boards manufactured. However, you still don’t have a circuit diagram.
Create circuit diagram
Of course, you can’t create a schematic directly from the Gerber files. However, you can read the Gerber files in a CAM editor. Then you can see the board in front of you, similar to a Gerber Viewer. Only here you can edit it and export further files:
Here you can now create a netlist. This list contains all connections. So which contact or soldering point has a connection with which or which other points.
You can even group the individual components beforehand. So the soldering points of a component can be defined as a component. So you have in the netlist already a labeling of individual lines.
After exporting the netlist, it is loaded into any board layout program. Here the assignment between the component and the netlist must be made.
If you have previously made the effort in the CAM Editor, and the components on the one hand grouped and also the lines assigned meaningful names, it is now easy here and the whole is ultimately a small piece of work.
Up to the reading of the netlist it was actually only a few steps, and the workload was relatively small and simple. The assignment of the netlist is a bit more work. And the more lines on the board are present, or solder points, the more effort you have. Especially since this work is still the most annoying, because it’s really just a hard work, similar to sorting socks 🙂 .
The circuit diagram
Now, of course, the actual circuit diagram must be drawn. The effort depends on the amount of components and their connections. Depending on the size and effort, the creation of the circuit diagram costs another good half to a whole day.
But after that you have a faultless schematic, if you did not make a mistake when drawing at the beginning and assigning the netlist.
But the subsequent result is then rewarded for the effort before.
This basically takes care of the worst. Now you only need to create a new board, export the Gerber files and order new boards.
What happened to the original circuit board?
This one enjoys the best of health! 🙂
I have reassembled the circuit board. In addition, I have now socketed all components. And of course it works again:
A new PCB
And this is how the new board looks like as a 3D view:
The outline is the same as the old board, so it would fit back into the case. I have taken over the component arrangement almost 1:1, except for a few small adjustments. At first glance, the new board looks like the original board.
In addition, however, I have accommodated significantly more blocking capacitors. These are all below the IC sockets. There they used the least space and thanks to the sockets you can place them there without any problems.
Of course, you could also use corresponding sockets with already pre-mounted capacitors. Personally, I don’t find these as attractive due to the higher price. But both ways are open.
No SMD components have been used, so the rebuild should be quite easy.
Here you can see the assembled board:
I have uploaded the board at PCBWay, so that it can be ordered there quite simply:
The assembly is quite simple and there is nothing special to consider, so that the card should not cause any problems even for less experienced beginners.
|Quantity||Designator||Manufacturer||Manufacturer Part Number||Description|
|1||C1||KEMET||C315C101K5R5TA||Capacitor, Ceramic, 100Pf, 50Vdc, 10-% Tol, 10+% Tol, X7r-Tc Code, -15, 15%-Tc|
|17||C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18||KEMET||C324C104J5R5TA||Multilayer Ceramic Capacitors MLCC – Leaded 50volts 0.1uF 5% X7R|
|2||CN1, CN2||Reichelt||https://www.reichelt.de/cinch-einbaubuchse-farbcodierung-schwarz-vergoldet-cbp-g-p6485.html?CCOUNTRY=445&LANGUAGE=de&trstct=pos_0&nbc=1&&r=1||CBP-G Cinch-Einbaubuchse, Farbcodierung schwarz, vergoldet (Reichelt)|
|1||CP1||KEMET||T330A475K025AS||Tantalum Capacitors – Solid Leaded 25volts 4.7uF 10%|
|1||D1||NXP Semiconductors||1N4148||NEXPERIA – 1N4148 – DIODE, 1N4148 AMMO-BOX 10K|
|4||Q1, Q2, Q3, Q4||Diotec||2N3904||Bipolar Transistor, TO-92, 40V, 200mA, NPN|
|1||Q5||Central Semiconductor||2N3906||Bipolar Transistor PNP Amplifier/Switch 40V 200mA 3-Pin TO-92 Through Hole Box|
|1||R1||Yageo||CFR-25JB-52-47R||RES 47 OHM 1/4W 5% AXIAL|
|2||R2, R3||Yageo||CFR-25JB-52-750R||RES 750 OHM 1/4W 5% AXIAL|
|1||R4||Yageo||CFR-25JB-52-1K5||RES 1.5K OHM 1/4W 5% AXIAL|
|1||R5||Yageo||CFR-25JB-52-2K2||RES 2.2K OHM 1/4W 5% AXIAL|
|2||R6, R8||Yageo||CFR-25JB-52-470R||RES 470 OHM 1/4W 5% AXIAL|
|1||R9||Yageo||CFR-25JB-52-82R||RES 82 OHM 1/4W 5% AXIAL|
|1||R10||Yageo||CFR-25JB-52-220R||RES 220 OHM 1/4W 5% AXIAL|
|1||RN1||Vishay Dale||CSC10A0110K0GPA||RES ARRAY 9 RES 10K OHM 10SIP|
|3||U1, U2, U3||Panasonic||SN74LS157N||Datenselektor/Multiplexer 2 zu 1 DIP16|
|2||U4, U13||STMicroelectronics||M27C64A-15F1||IC EPROM 64K PARALLEL 28CDIP|
|3||U5, U9, U16||Texas Instruments||SN74LS04N||IC HEX INVERTER 14-DIP|
|1||U6||Texas Instruments||SN74LS74AN||TEXAS INSTRUMENTS SN74LS74AN Flip-Flop, with Set and Reset, Complementary Output, Differential, Positive Edge, D, 13 ns, 33 MHz|
|1||U7||Texas Instruments||SN74LS10N||IC GATE NAND 3CH 3-INP 14DIP|
|1||U10||Toshiba||TMM2016AP-10||Integrated Circuit Memory 2016/TMM2016AP10 TOSHIBA Static RAM memory prog. volatille KX8=2|
|1||U11||Texas Instruments||SN74LS245N||IC TXRX NON-INVERT 5.25V 20DIP|
|1||U12||Texas Instruments||SN74HC273N3||Octal D-Type Flip-Flops With Clear 20-PDIP -40 to 85|
|1||U14||Texas Instruments||SN74LS86AN||IC GATE XOR 4CH 2-INP 14-DIP|
|1||U15||Texas Instruments||SN74LS164N||IC, 74LS, 74LS164, DIP14, 7V|
|1||U17||Texas Instruments||SN74LS166AN||IC, SHIFT REGISTER, PDIP16, 7V|