Taito TC0070RGB replacement

Several people asked me about a possible replacement for the Hybrid used on several Taito games as they have boards where these have failed.

Original TC0070RGB – connected to socket since many of the legs were broken!

I drew up a possible circuit, and then JROK decased one and put the schematic for that up on a forum. Between my version and the real thing, I put together a PCB that will allow two GAL’s and a pile of resistors to be used to create a functional replacement.

Replacement version fitted to Rainbow Islands PCB

As you can see, the replacement is not quite as pretty, but is made from fairly easily sourced components that you can get from ebay or remove from old parts PCB’s – street fighter two bootlegs are usually a good source for GALs.

Screen shots from the installed device are shown below.

Colour Test screen
Rainbow Islands

To build one of these yourself, you will need the following :-

Parts to build RGB Hybrid
  • 1 x PCB (Gerbers here)
  • 2 x GALs and the JED files (20V8 or 22V10)
  • 3 x transistors C1815
  • 3 x each resistor – values 100, 1k, 2k, 4k, 8k and 16k ohms
RGB Hybrid PCB

You can see the component values clearly marked. Resistors are marked to the right of the holes, so 16000 (16k)  is at the top right.

You don’t have to fit sockets but since I was still testing at this stage the sockets allow me to change the GAL code much easier.

I normally start fitting the resistors from right to left (I’m right handed – makes soldering easier) and it’s then easy since you go in the pattern 16k, 8k, 4k, 2k, 1k – repeat that twice more, then fit the final 100 ohm resistors and the transistors.

When you cut off the extra legs from the resistors, save them, because they are what I use to make the 25 “legs” needed to connect the PCB to the main board.

Almost completed PCB

See above for finished item installed on Rainbow Island PCB.

Bubble Bobble

I was sent a Bubble Bobble PCB, which does not use this hybrid, but uses three PC040 DAC hybrids instead. These are also beginning to suffer the same fate, and on this particular PCB all three were dead.

The circuit for the PC040 shows it to be a 6 bit DAC, whereas the TC0070 is only a 5 bit DAC, but checking on the schematics shows that for Bubble Bobble only 5 of the bits are used, with the lowest bit being connected to GND.

So I thought it may be possible to use one of these on that PCB as well.

Wiring for RGB Hybrid on Bubble Bobble PCB

It was never designed to be used on a Bubble Bobble PCB, but it worked for me. It just needs wiring up to where the ‘040s used to live.

For anyone interested in using it like this, you need to remove resistors R2,R3 and R4 and the three PC040s. Where no IC number is given you can connect to any of the three PC040 positions (because it is the same signal)

Installed on Bubble Bobble PCB

you can see in the photo that I picked 5v up from nearer to the connector as well (normally pin 5, But I used the other end of the resistors I removed.

Screen from Bubble Bobble

n.b.

I have used these RGB output PCB’s on several of my Taito PCB’s, and other people have used them as well. As yet no-one has reported any problems.

I can not guarantee that it will work on your particular PCB, although I have no reason to think that it will not!