Building the ReCD32
Posted on 2022/10/12 | by | 1 comment

As usual on all my guides: PLEASE Read the guide first. prefferbly BEFORE ordering components or so. also follow it. the reason why you do it in steps is to catch errors so you do not have a completly built board and then try to start it and it will not start.. and if stuff doesn’t work as in the guide: check what you have missed. if it is not in the guide: I have not idea either. 🙂

The CD32 is very special, so if you lack a component from the BOM. it means you will need to transfer it from a old board.

Anyway as usual. put all passives on the board. Resistors, ceramic capacitors, diodes etc. leave the electrolytic capacitors. A note about U14 and U49, on the original CD32 it is using a component that are not produced anymore. you can use that one OR the small 3 pad (SOT-23A-3 ) location with a TC54VN4302ECB713. NOT both.

AND CD32 have a addon throughhole resistor at U49, this is not needed as it is fixed on board.
(Most of this guide works for CD32 clone aswell. but you are on yourself when it comes to parts I have changed in the ReCD32)

Anyway Locator for the project you can find at: https://locator.reamiga.info/locator.php?project=ReCD32

Project webpage for the ReCD32 you can find at: https://www.reamiga.info/?page_id=148

Anyway. A board with all passives on:

I have put Kapton-tape on the connector here so IF I by misstake drop solder or so on the connector it will not damage it.

First time to get power to the board.
Solder in the Powerconnector and 3 throughhole ferrite beads as filter.

A note. on the BOM I have the switch is not 100% perfect. it have a small distance:
This will put the switch too high. so we need to fix this: you can bend it back:
Wiggle it and cut it off:
Solder it into place, you will notice that the pins are too deep in so you will need to trim the pins slightly:

All in place and power it on:

The led for +5V will now go on.

Time to add 28MHz clock:
Put in the 28MHz oscillator (ACTUALLY for a more easy build do this AFTER LISA but I want to point out what is needed for the 28MHz to work.
U25 (74F00)
Now there should be a 28MHz systemclock. (but as told. wait with the 28MHz AFTER you soldered in LISA) even if I now show picture with 28MHz in place: (probe where you can check for a 28MHz signal)

Anyway time to get V and H sync working:

Add LISA, ALICE, AKIKO, U61 (74LS08), U34 (74LS166) and the VGA Connector.
(and the 28MHz oscillator if you haven’t put it in yet)
(CD32 clone builders cannot do a VGA Connector)

You can now get a (15KHz) sync on the VGA Connector. OR you can probe V and H sync on the left pad on the 2 resistors right of ALICE. or one of the testpoints of the board.

Now time to get some code running.

First. in this build I am using 32 bit roms instead of standard 16bit. Remember that the BOM includes stuff for this. so if you do NOT want to use 32 bit roms. you can skip one 42 pin socket (U6B) also you can skip XU1 and the jumper. (remember to remove from BOM when ordering).
HOW to burn 32 bits roms etc. this is not the guide for that. it will be up to you. Anyway the rest here is with 32 bit roms.

Anyway add XU1 (74F125) (SKIP this for 16 bit (original) ROM)
Add jumper-header for 32Bit rom at right botton. (and put a jumper there) (SKIP if 16bit)
Put in ROM sockets (ONLY U6A for 16 bit)
Put in CPU and U37 (74F86) (NOTE: on OLD pre-release CD32 boards from me silkscreen is wrong way on PCB. follow direction on the locatorscreen).
Put in DiagROM as rom.

Cpu now runs code, you will note it if you probe data/addresspins on the romchip that there is activity.

Here you see with 2 roms (32bit) also note that the bottom pins are not used when using 27c400 proms. (same as on 1200 etc) for 16 bit you have a 27C800 prom at the right socket.

Next step is Paula so add it. (NOT. prerelease CD32 boards, Silkscreen is wrong! put paula as in locator (and original board as shown on picture):

If you now poweron the LED led will flash some.

now time for a OPTIONAL addin: the serialport. (NOTE this serialport does NOT handle RTS/CTS handshaking) this is FULLY optional and not needed. (BUT is in BOM so remove components if you do not want it). there is a location for a header if you are happy with a 5V serial signal but as normal serialport does not use 5V. I added this feature.

Add U50 (MAX232)
and the 10 pin header.

Now you can attach a serialcable there (Standard PC motherboard pinout)
And you will get serial output on DiagROM via normal RS232:
if you skip serial (or have CD32 build) you can use the 5V signal to the right. or the classic CD32 way on the keyboard connector (not soldered in yet) but there: you are on your own. OR.. just skip it and work in the dark for a while.

To get RAM working:
Add U35 (74F373)
and the RAM Chips. (every chip is 8 bit if you run diagrom between the chips)
Time to get something on the screen. (CD32 clone builders are somewhat “on your own” here)
Add the VideoDAC (U30) (ADV101)
D215 (LM386)
U36 (74HC4066)

and now you should get stuff out on the VGA port. (NOTE!! 15KHz).

Put in a jumperheader at PAL/NTSC location and put a jumper at desired more (and 0ohm resistors between correct pads). Also add the Composite video connector.
to get picture out you will need one cap as shown. this will give some kind of picture on composite (on PAL most likly black/white to be fixed later)

Now it is time to add stuff for audio, extra videomixing (from FMV card etc):
add:
U15A, U15B, U38B (LF353)
U38A (LM358)
U39 (CXA1553)
U31 (LC78835M)
U22 (74HC4066)
U32 (78L05)
X3 (16MHz)
RCA Plugs for Audio.

Now you shold be able to run normal Kickstart. so you can test it:

On this picture you can see that I put in a 16bit rom. you can still do that even if you soldered stuff for 32bit. you just remove the jumper to the right of the ROM and original 16 bit roms works fine.

you shold get the famous CD32 animation. (on Composite on PAL will be black and white etc) and no audio yet!.

Lets add the small NVRAM.
Add U9 (24C08)


also on the location marked Q765, schematic say it is a small transistor. so I move that chip that is on the cd32 🙂 )

Now add the 4MHz Oscillator for PAL Composite output,
Also solder in S-Video connector.
and add the Trimcap (I DO recoment putting it AFTER cleaning however)
also add the connector to the CDROM. (there are 2 types on original cd32 etc so this is why the connector is “odd” same on original machine) note rotation of the connector:

I lifted up the latch here so you can see more easy how it should be rotated.

Now solder in the rest of connectors, DSub, Led board, amd Keyboard.

Now clean board from flux etc. (like in ultrasonic)

and after that add your electrolytic capacitors: (and NO! you do NOT use Ceramic or Tantal capacitors they behave different! use high quality electrolytes)

So lets start it up:

CD32 in all its glory!

you MIGHT need to adjust the trimcapacitor close to the 4MHz oscillator to get proper color output on SVideo/Composite for PAL.

Enjoy!

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One thought on “Building the ReCD32”

  1. Hi John,

    I have a rare Commodore prototype I think you maybe interested in. If you send me an email; I would be willing to send it to you to reverse engineer.

    Sorry to post this in your comments however I cannot find any other way to contact you.

    Let me know?

    Michael

    Reply

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