Project to install LC575 Analogboard on Color Classic

Last week the shipping company destroyed the LC575. I changed my mind and decided to collect the garbage parts to make one. When I  had a CC that was in a bad state (I couldn't use logic board, analog board and floppy drive), so I decided to make one with my spare parts. I've always liked 68K compact Macs. Most of the parts were sleeping at home. It will be about 25 years long…

The base CC was the worst individual I had. BTW, Is the PIC beautiful? Actually I was thinking of selling it on e-Bay lol, but even if the condition is very very bad, CC is rare computer. The case is a bit missing, but was it dropped by someone? Originally, this was in my home in this state. It's out of the question, but CC was disassembled, washed and bleached after this. It can hardly be reused except for CRT and wiring.

Let's get back on track! The benefits of using the LC575 analog are many. The power inlet and the slot of the main body can be placed in exactly the same position. Fan connector locations also. Although not measured, it can be assumed that the power supply is powerful because of its large power supply capacity (because there are mounted parts such as a CD drive). There are also default stereo outputs for the built-in speakers. *There is a little issue but I’m currently investigating.

*Sorry, This is the pic after cutting.

I'll tell you not to get confused, but since the LC575 logic board is used by connecting it to the LC575 analog board, the environment before the CRT output is exactly the LC575 itself.

After that you have to change the CRT output, It should be done in line with the change from a 13-inch to an 11-inch Trinitron CRT. If you do not do it, it will be displayed, but it will not be full screen like the image.

As will be described later, this modification requires CC’s original FBT (flyback transformer). And VGA (640X480) output is possible with genuine specifications. Moreover, like the genuine LC575/550/520, the logic board (motherboard) can be replaced without modification (Pin-out mods), and you can boot from any of them. If you replace this with CC, VGA can be started for both CC I and II.

I haven't tried it, but I think you can get the same results with the LC550 and LC520 analog boards.

Also, as for me, I am not a professional (not 100% amateur because I have a background as an electric guitar designer) and 100% do not understand the concept of this analog board. Please let me know if the description is incorrect.

To install LC575 analog board

If the CC analog board is broken, you can replace it with the LC575(550/520) analog board for repair with little work. I’m gonna teach you the process. 

Originally, this analog with genuine VGA output has plenty of power capacity, and it is suitable for converting color classic to PPC or 68040.

important point! : If you get an electric shock from my article or your important ColorClassic breaks, I take no responsibility.

Things necessary：

1, FBT(flyback transformer) 157-0146 will be reused, so it must be usable. And CC Brocken Analog board.

2, LC575 analog board *Use a fully operational product. Maybe needs Re-cap.

Required processing location：

1，PCB cut left and right is 19mm(0.75 inch).

2, Move with a jumper with a pattern that crosses the cut line.

3, Replace few parts from CC analog board.

4, Replace FBT from CC board.

5, Installing the speaker cable from LC575 board. *Stereo possible.

6, Chassis rail processing (cutting)

7, Processing of analog board earth plate and replace connector cover.

8, CRT yoke plate ring and analog pot adjustment

Issues:

1, Stereo output does not sync left and right.

2, The horizontal adjustment area is slightly narrow. Approximately 4 mm (0.16 inches) outside the display screen area. I will talk about this at the end of the sentence.

Working method

1，PCB cut, The hardest work

Cut with 19mm cut lines on both ends. I make a notch on the P-cutter（OLFA 1090486 PC-L Plastic/Laminate Scorer) from both sides of the PCB.

At this time, pay attention to the pattern on the right side from the back. Separate it here and reuse it. The two resistors that are exactly on the cut line are transplanted to the side of the main analog board ( ↓see the bellow). Then, when separated, cut the four ends diagonally.

The transistor and the potentiometer on the cut line are remove once at this point. *Will reuse later.

In particular, make a large diagonal cut so that the part that hits the claws of the chassis does not hit.

2，Jumper handling

Move with a jumper with a pattern that crosses the cut line. Connect the 6 jumper wires to the positions shown in the image. Use the extra holes to thread from front to back. Make sure the jumper wire is in its original position so that you do not make a mistake.

At this point try connecting to the LC575 once and see if it works. *If you have the LC575 body

*Separated PCB with double-sided tape.

3, Replace Few parts circuits from the CC board.

I transplanted the parts in this area one by one for confirmation, but as a result, I did not see a big change. So if you are worried, try replacing it!

If you just move it, it is not an important task, and when you try it,　With or without replacement both parts will work. However, there are differences in the following parts as the circuit to the FBT, so I replaced them in my case. 

I’m not even sure about the circuitry on this analog board, but perhaps this blue box is an FBT amplifier. Since the FBT is different, it seems that it needs to be replaced, I believe it is the only incompatible part.

Looking at the back side, there are not enough patterns, so add jumper wires using through holes.

The following differences were discovered, but no major change was seen even after replacement:

- firm capacitor, the withstand voltage is the same, but the values were little different when measured. But don’t need to replace it.

- CRT back PCB, It seems that they are using the same one, but I changed it considering the cable handling. Since there is a difference between the snap mount and the solder mount, in the case of the snap mount, the snap receiving side is also replaced.

- Coils, they seems same parts for me…

- Blue disc type capacitor, which is not mounted on CC. No change was seen. I don't care if you have it or not. It may be a kind of smoothing circuit.

*Important: Wear insulated gloves to prevent electric shock.