Build and Installation of the Einstein TC-01 V9938/V9958 Adapter

Warning

Please note the following before you start:

1. This project is not for those unfamiliar with the use of a soldering iron.
2. The information in this guide is for general information only.
3. The Einstein TC-01 is well known for its fine traces, which can easily be damaged if you are not extremely careful.
4. By using this guide you agree that you do so entirely at your own risk, and you take full responsibility for any outcome, damage or loss that results.

Introduction

The Einstein TC-01 has recently gained a whole host of new expansion and upgrade boards from the Board-Folk team. One of them goes far beyond anything expected: the V9938/V9958 adapter. It replaces the TC-01's video chip with a Yamaha V9938, the chip in the Einstein 256, or a V9958, with 192K of video memory; with the 256's own ROM, MOS 2.1, fitted as well, the TC-01 starts up as an Einstein 256.

The work is: build the adapter board, remove the TC-01's TMS9129 video chip and fit a socket in its place, replace the voltage regulator, fit the board, and write and fit a patched MOS 2.1. All of it is covered below, and I recommend reading the whole guide before you start.

I wrote this after fitting the board to three TC-01s. That is not to say I had no problems: I damaged a trace on one of the boards, though I repaired it easily and all three Einsteins now work. I mention it to make the point that the upgrade is very possible, but the utmost care must be taken not to damage your machine.

When you have finished, your TC-01 will have the 256's better graphics and larger video memory, running a patched MOS 2.1, with full colour 80 column text as well as the 32 and 40 column modes. It is not identical to a 256 in every respect: the 256 has a port at 26h, for the Alph key, that the TC-01 does not, which is why the ROM needs its patch.

The board was designed by Ian Cudlip of Board-Folk; his notes are in Einstein TC-01 V9958/V9938 VDP Adapter, and the Board-Folk Einstein TC-01 upgrades are on GitHub: Board-Folk/Einstein-TC-01.

What You Need

1. A small, sharp pair of wire cutters
2. A decent soldering iron
3. A solder sucker
4. Flux
5. A large amount of narrow solder wick
6. An anti-static soldering mat to work on
7. An anti-static wrist strap, to avoid damaging the chips you handle
8. Some 30 gauge PVC hook-up wire
9. Isopropyl alcohol (IPA) and cotton buds, or IPA wipes
10. A blank V9938/V9958 adapter board. The Gerber files are at Board-Folk's V9958AdapterTC01, and can be used to order boards from suppliers such as PCBWay or JLCPCB.
11. The parts in the bill of materials, which is on the same page and in the appendix below. The V9938 and V9958 chips are often counterfeited, so buy from a reliable source; for the record, I bought all three of mine from utsource.net.
12. A Traco TSR 1-2450 voltage regulator, which is not in the bill of materials. Board-Folk found that the factory regulator, an LM350T5, overheats with the adapter fitted and cuts out, crashing the machine; it needs replacing with a compatible regulator rated at 1 amp or more.
13. An EPROM programmer that can write a 27C128, and a blank 27C128 EPROM
14. The patched ROM image, MOS 2.1 patched for the TC-01, from our downloads

Assemble the Adapter Board

Using the parts from the bill of materials, your anti-static mat and wrist strap, soldering iron, solder, flux and the layout below, assemble the board. To avoid problems seating the chips, I strongly suggest fitting dual wipe DIP sockets for the memory and the video chip.

When you have finished, clean off the flux with IPA and cotton buds or IPA wipes.

Now solder one end of a length of the 30 gauge wire to pin 3 of I28 on the main board, shown below. Be careful: do not use too much solder, and make sure you do not short any of the surrounding pins.

When the adapter is fitted, the other end of this wire is soldered to the A1 pin on the board's two pin header (the pin marked with a box). Address line A1 is not present on the TC-01's video chip socket, and the board will not work without it.

If you are using a V9938, there is a solder bridge on the underside of the board that is needed only for the V9958. Cut it with a sharp blade, then check with a multimeter that the two halves are no longer connected. If you skip this, the board will not work properly.

Write Your MOS 2.1 EPROM

Now prepare the ROM. Download MOS 2.1 patched for the TC-01, put a blank 27C128 in your EPROM programmer, and write and verify mos21.tc01patched.bin. Then put the chip somewhere safe: you do not want its pins bent. Creating an EPROM for the Tatung Einstein TC01 and 256 explains how to write one.

The image is the 256's MOS 2.1 with three bytes changed. On a TC-01, the unpatched ROM reads the Alph key from port 26h, which the TC-01 does not have, and Alph lock can switch itself on and off; the patch, from Board-Folk's notes, stops it reading that port.

Take the Main Board Out of the Case

1. Turn off your machine and disconnect all the cables.
2. Remove the two screws on the back of the case, lift the lid from the rear, and put it somewhere safe.

3. You can now see all the screws holding the main board in place, but before removing them you need to take out the power supply. Look in the gap between the disc drive and the power supply: there are two screws. Remove them, take out the metal plate they hold, and lift the power supply out.
   If you have bigger hands, it may help to take the first disc drive out of its cage to reach those two screws. Undo the four retaining screws, slide the drive back, tilt it and lift it out. If you disconnect the cables from the back of the drive, make a note of how they were connected, as you will need to put them back the same way.

4. If you have a second drive fitted, take it out of its cage as well.
5. Remove all the screws from the main board.
6. This part is, I am afraid, never simple. By carefully jiggling the main board, lifting it slightly on the power supply side, and with a great deal of patience, ease it out of the case. On some Einsteins you can take off the volume knob on the right side of the case to give yourself more room.

The Difficult Bit

Everything so far was preparation for this. This is where a silly mistake can ruin your Einstein's main board, so, one more time:

1. This project is not for those unfamiliar with the use of a soldering iron.
2. The information in this guide is for general information only.
3. The Einstein TC-01 is well known for its fine traces, which can easily be damaged if you are not extremely careful.
4. By using this guide you agree that you do so entirely at your own risk, and you take full responsibility for any outcome, damage or loss that results.

If you have decided to go ahead, you now need to remove the video chip and the voltage regulator, both shown below.

There are two ways to get the chip out.

A. The destructive but easy way. Cut every pin away from the chip, where the pin meets the chip itself, with wire cutters. Then heat the solder on each pin in turn from the underside of the board, and lift the pin out from the top with tweezers. Do not use force: wait for the solder to melt, so that the pin comes out by itself, or you will damage the board.

For: easier, quicker, less risk to the main board. Against: you have destroyed the original video chip, and there is no going back.

B. The careful, non-destructive way. Put plenty of flux on every pin and use solder wick to remove all the solder, until the chip can be lifted out gently in one piece.

For: the chip survives. Against: any pressure on the chip risks damaging the pads on the main board, it is very slow, and if you do damage the board you will certainly regret it.

I nearly always choose A, because I put the safety of the main board above everything else, but the choice is yours.

With both parts out, fit a 40 pin socket where the video chip was, and fit the Traco TSR 1-2450 in place of the old regulator. Make sure the Traco goes in the right way round: a regulator fitted the wrong way round, or the wrong regulator, will do serious damage.

If You Damage a Pad or a Trace

This is not good news, but keep two things in mind. First, a problem now is not necessarily your fault: these machines are old, and they do fail when modified. Second, there is no need to panic: most damage can be repaired, though not all of it.

I warned you about this earlier, but I did not want to leave anyone stuck, so here is how I fixed the damage on my own board.

What the Damage Does

In the picture below one pad has lifted, so nothing can be soldered to it. You can also see the traces running to the pads; perhaps it is one of those you have damaged. Either way the problem is the same: parts of your computer can no longer talk to each other, and you have to fix it before you can go on.

Vias

I made my repair using the main board's vias. A via is a small plated hole that carries a signal from one layer of the board to another, a vertical bridge for a trace. They make excellent places to solder a repair wire.

Making the Repair

Turn the main board upside down and, starting at the damage, follow the trace leading to and from it. In the example below (not an Einstein) they are easy to see. The trace between the two red arrows, and between the two blue arrows, is clear: the silver pad is most likely what you have damaged, though it may be a trace; either way the repair is the same. Look closely at the pad at the blue arrow and you will see a trace going to the second blue arrow (the via), and another leaving the same pad for one of the edge connector pads at the top right.

• If you have damaged the trace between the pad and the via, relax: you need do nothing.
• If you have damaged a trace leading to another part, solder a length of the 30 gauge wire from the pad to the trace's destination (in the example, the edge connector pad), bridging the damage. If the destination is a long way off, scratch away a little of the trace's coating on the far side of the damage and solder the wire from the pad to the bare trace instead: the longer the wire, the more chance the signal degrades and the fix fails. This is a little harder, especially where the trace is narrow and close to others.
• If you have lifted or damaged a pad, solder the wire between the pin coming through the hole (where the pad was) and the via.
• If you have lifted a pad and its trace, do both: from the via to the pin, and from the pin to the trace's destination or to the bare trace.

After each repair, set a multimeter to continuity and check that the points are connected. If they are, and you have not damaged anything else along the way, you have quite likely fixed the problem.

If you still have a working TMS9129, plug it into the new socket and check the computer works. If, like me, you destroyed it getting it out, you will have to wait until the end of the project to test.

If a repair fails, go back, look for any other damage, check your connections again, fix what you find and test again. If the machine still does not work, I am afraid it is time to find professional help.

Fit the Adapter Board

First remove the four jumpers from the jumper block shown below.

Place the adapter over the video chip socket, line its pins up with the socket and its plug with the jumper block, and push it down carefully until it is firmly seated.

Now connect the wire you soldered earlier to the A1 pin. If you forget this, or the joint is bad, the board will not work, so if anything is wrong this is the first thing to check.

When you are sure everything is right, it is time to test your work. You have not fitted MOS 2.1 yet, but if everything has been done correctly the board works with the TC-01's own MOS 1.2: it will not behave like a 256, but the display will be improved.

If your Einstein boots to MOS 1.2 and all looks well, check the keyboard and load a game. When you are happy, turn everything off: it is time to fit MOS 2.1.

Carefully remove the original MOS ROM and fit the new MOS 2.1 EPROM in its place, the right way up, with its notch towards the back of the case.

Turn the machine on, and if everything has been done properly you will see the Einstein 256 start-up screen. Test everything again, then press CTRL and P followed by RETURN: you should now be in full colour 80 column text mode. Repeat the command to go back to 40 columns.

Congratulations: your TC-01 now starts up as an Einstein 256.

Appendix: Bill of Materials

From Board-Folk's V9958AdapterTC01, where the up-to-date list is kept.