Tatung Computers

Overview

The Einstein TC-01 (also TC01, and affectionately as Albert), available in 1984, features no built-in programming language unlike other computers of the time, instead the TC-01 runs a CP/M compatible O/S from floppy, Xtal/DOS, from which any manner of software - programming language, word processor, etc - can be loaded. Powering the TC-01 is a Zilog Z80A clocked at 4 MHz, with 64 KB of main RAM, 16 KB video RAM, 8 KB ROM (can be expanded to 32KB internally), and capable of (for the time) hi-resolution 256 x 192 graphics, 16 colours, and 32 sprites.

The computer originally came with a UHF TV lead, system master disc, introductory manual, BASIC reference manual, BASIC quick reference card, and DOS/MOS manual.

At the front of the computer you will find an 'Tatung Einstein badge' to the left, the keyboard in the middle, and further back two lights (green for power, and red for alpha lock when in all caps mode) on the left along with a 3" inch disk drive (0A), and if fitted, a second drive (1B) to the right of the computer. The keyboard is full QWERTY and has 67 keys in total, 48 white alphanumeric/graphics keys, 8 grey function keys, 11 control keys (grey except for the enter key), the keys have programmable automatic repeat delay and speed.  At the rear of the machine are the following; 6-pin DIN carrying YUV/RGB video (internally selectable between the two), 17x2 male IDC Centronics compatible printer connector (parallel printers), 8x2 male IDC user I/O port (various digital interfaces), 30x2 male IDC Tatung pipe connector (80 column interface), 17x2 male IDC external disk drive connector, reset button, mains power lead, and power switch. Under where the power cord enters the computer is a label declaring the model number (TC01), serial number, power requirements (220 - 240 V ~ 50 - 60Hz, 30 watt), and copyright dates (1982, 1983, 1984).

On the right of the machine is an RF TV phono connector, volume knob for the internal speaker, two 7-pin female DIN connectors Analogue 1 and 2 (paddles, joysticks, etc.), and RS 232C 5-pin female DIN connector (serial printers, modems, etc.).

There are a number of expansions for the TC-01; up to two self-powered 3"/3.5"/5.25" floppy drives can be added through the external disk drive connector, and an 80 column card was also available.

Repair

Teardown

It's very straightforward to open up the TC-01, simply remove the two screws at the back of the machine and lift the top piece of the computer case off while pulling away from the keyboard end. When putting the top piece back on make sure it lines up correctly with the rest of the case so that the screw holes are accessible, then the screws can be put back in.

You will see that there are several main components in addition to the motherboard, all of which connect to the motherboard; the power supply, floppy drive(s), loudspeaker, keyboard, and LEDs.

**** PLEASE DO NOT EVEN OPEN UP THE POWER SUPPLY UNLESS YOU HAVE EXPERIENCE WORKING ON MAINS POWERED CIRCUITS ***

To remove the PSU, loosen the two screws between the PSU and drive 0/A, you can then lift up the PSU and remove the connector from the motherboard (M007). To open up the PSU, remove the two screws from the top of the PSU case and lift the top piece up and off. Note that the screw near where the mains power lead enters the PSU holds the earth wires to the case. 

Now that you have access to the power supply circuit board it's a good idea to inspect it for any obvious signs of components that have gone bad, in particularly burnt components, such as diodes, and leaking or bulging capacitors. The fuse (FE01) is type T1A 250V time lag and can be replaced once the reason for it failing has been identified and fixed. You may notice a white substance on the mains filter choke (ZE01), either partially covering it or completely, this is quite common and can be cleaned off without any concern other then checking the choke hasn't failed.

When putting the top piece of the PSU cover back on, make sure to tuck the power wires in, and then tighten the two screws back into the case. To put the PSU back into the computer, first put it in place and push toward the rear of the computer so that the two tabs attached to the case insert into the PSU case, then you can push the metal tabs toward the PSU so they insert into the PSU case, then the two screws can be tightened. Don't forget to plug the power cable back into the motherboard.

Some people choose to replace the original power supply board with a modern equivalent (whether it has failed or not) mounted in the original PSU case, I strongly recommend to do so as a safer option than trying to repair the original power supply. Additionally, a modern PSU is likely to be smaller and lighter than the original one and exceed the power requirements of the TC-01, so the power supply will be less stressed.

You can check out a guide for replacing the PSU by following this link:

http://primrosebank.net/computers/einstein/einstein_psu_rep.htm

Note that the chosen replacement PSU, a Mean Well PT-65B, has universal input voltage, and its outputs are rated at 5VDC at 7A. +12VDC at 3.2A, and -12VDC at 0.7A.

I bought my first TC-01 from eBay and after an inspection of the PSU's internals I didn't see any obvious signs of potential problems but after a short while of using the computer, I heard a bang and the computer switched off. Opening up the PSU I found that the fuse had blown as can be seen in the following image:

You can find the schematic for the power supply on page 50 in the hardware manual (see Resources section) should you want to repair it.

I did attempt a repair but even after replacing a transistor, which was what was causing the fuse to blow immediately upon the PSU being switched on, I decided to look for a replacement PSU, as the fuse continued to blow due to another fault, and long run it was probably better to use a modern power supply.

Although I could have bought a replacement PSU I found I already had a suitable power supply that I had taken from an external SCSI CD-ROM drive, model number XY649. The power supply delivers +5V and +12V (I measured +4.86V on the 5V rail and 11.55V on the 12V rail while powering the computer) but doesn't output -12V, but from what I can tell the TC-01 only uses that voltage rail for RS232C so it was an otherwise suitable solution and I could always use an alternative power supply in the future.

This is how I installed the replacement power supply in the original case: first I removed the L and N wires from the switch, and the earth wire from the where it's secured to the case. Since I needed the output voltage connector I desoldered that from the original PSU board and then soldered the wires (apart from the -12V one, which I isolated) to the wires on the replacement power board. As the replacement supply had its own power switch I desoldered that and bridged the contacts on the PCB only to realise that the switch is N.C,, so I cut the bridge on the PCB.

I later returned to the power supply and added a small board in which I had soldered up a -12V linear power supply, which uses a stepdown transformer, bridge rectifier, regulator and smoothing, along with an output fuse. You can see both power supply boards below, the board I soldered (top) along with the the 5V/12V power supply (bottom):

The schematic for the -12V power supply I made follows and can be downloaded from the bottom of the page (Tatung_Einstein_-12V_supply_schm.jpg):

KiCad 9.0.0 was used to create the circuit diagram, the date on the schematic reflects the digital version based on the original hand drawn diagram I made before soldering the circuit.

The circuit is designed for UK mains (230VAC).

The switch, SW1, is the one already in the PSU.

I used a transformer (type XT1109) with centre tapped secondary windings, this isn't necessary and was due to it being a suitably rated transformer I happened to have at hand, you can see in the photo above the unused white transformer centre connection.

Although the TC-01 mains plug is fused I put a low current fuse, F1, on the secondary side of the transformer. I used a typical cartridge mains type fuse since they are readily available but of course you can use one rated for a lower voltage, just make sure it's rated for 100mA and is designed to blow quickly.

The bridge rectifier, D1, is type DB106 and is quite overpowered (1A rating) but I used it as I had it in stock and it was small, you can use a lower rated one as it only has to handle less than 100mA.

Resistor R1 limits current to the input of the voltage regulator, U1, but needs to be rated for 2W.

You can use a 79L12 rated for 100mA instead of the 'standard' 1A 7912 I used since I had plenty of them, either way, a heat sink shouldn't be needed. If you look at the power supply schematic in the hardware manual you will see that they used a 79L12 with series limiting resistor, the difference to my circuit (which is a simple linear supply) is they used a single diode (DE12) to rectify the transformer winding, forming a half-wave rectifier.

The U1 output connections need to be connected to the TC-01's power supply voltage connector that plugs to the main board - don't forget the common ground connection to the other power supply that supplies +5V and +12V.

I ended up getting a second TC-01 and the power supply on that one also blew after short use and although I looked to see if I had another suitable replacement power supply I decided to buy a ready made solution that supplies 5V, 12V, and -12V. The recommended substitute power supplies people recommend were a little bit pricey but I came across the Mean Well PT-45B for £13.10 ($16.39) rated 42.6W, delivering 5V/3A, 12V/2A, -12V 0.3A, more than enough power for the TC-01 and small enough to fit inside the original power supply metal enclosure. In the future I could buy another and install in my first TC-01 instead of the two separate boards.

Before installing the replacement power supply I powered the TC-01 from my variable PSU, temporary connecting with crocodile clips 0V, +5V and +12V to the motherboard power connector - be very careful if you do the same that you don't cause shorts. This confirmed that the computer hadn't suffered any damage and I saw a peak of +5V ~ 1.3A and peak +12V 0.75A, which gives a good idea of what the machine requires should you opt for a lower power replacement (you should add on for connected peripherals, however).

Going back to the PT-45B the datasheet can be found at:

https://www.meanwellusa.com/upload/pdf/PT-45/PT-45-spec.pdf

On the PCB it has what looks to be a model number, PT-65-R21VAI, which is possibly a generic number since the +/- voltage is set with SVR1 variable resistor, allowing the same board to be sold with different voltage ratings. On capacitor C5 it has a label with PT-45B written along with the power ratings.

You can see the PT-45B power supply installed in the original PSU case in the following photo:

Resources

TC-01 hardware manual

https://retrocmp.de/fdd/teac/Tatung-Einstein_01.pdf

Various manuals

http://www.tatungeinstein.co.uk/front/mans.htm

Software

Loading software

The TC-01 will only load system software off drive 0 and if you are fortunate to have original disks then you can load them using the internal drive, or you could replace the internal drive with a floppy drive emulator, such as a GoTek, giving you access to all the software you could ever need. However, you may want to keep the original mechanical drive installed and boot off a GoTek or similar device connected externally, but as mentioned, the TC-01 will only boot off drive 0. The workaround is to set the internal drive to drive 1 using its on-board jumper (see the Repair section for accessing the internal drive) by moving the jumper from DS0 to DS1, and the GoTek to drive 0 by using a jumper on S0 if using a twisted interface cable.

The GoTek can then be connected to the disk drive connector at the back of the computer but note that pin 1 isn't marked but is on the right of the disk drive connector when viewed from  the rear of computer. As with any externally connected drive, a GoTek will need to be powered off its own power supply as the TC-01 doesn't provide suitable power through the disk drive connector.

Games

We will look at some games available for the TC-01, starting with Pakman, an obvious clone of the classic arcade game Pac-man, which looks and plays decently but could have been better considering it only uses 'character' graphics, rather than taking advantage of the TC-01's sprite abilities. First, we have the title screen, followed by some gameplay:

Notice how the content isn't centred; this is indeed how the images are displayed by a TC-01.

Here is a video from YouTuber petsasjim1 playing the game:

Millipede, present along with Pakman on the same disk, appears to be inspired by the Atari game with the same name but with worse graphics and less gameplay features and enemies but nonetheless it's good fun, take a look at some screenshots:

There have been a number of ports of Monopoly to various computers and the version for the Einstein (see the next two screens) allows for 6 players (humans and CPU), with detailed graphics and decent animations.

My capture card seems to have lighten the images a bit too much judging by the title screen.

Lastly, we will briefly look at Konami disc arcade, containing four games; Kung Fu, Kings Valley, Time Pilot, and Comic bakery, shown in the game selection menu below:

I didn't do very well playing Kung Fu (see image below for gameplay) but it was good fun nonetheless:

Xtal DOS

Xtal DOS is the main operating System used on the TC-01 and various versions were released as will be seen as we look at different pieces of software to give a bit of an idea of some of the non-gaming titles available. But first, let's look at a simple DOS command, DIR, which lists the files available on disk:

If you see the cursor waitng at the end of the listing (as above) press enter for the computer to display the remaining files.

The first drive is '0', and the DIR command defaults to showing the contents of the first drive. Each file consists of a name up to 8 characters long, and an extension up to 3 characters long, which follows the filename and is separated by a '.' (fullstop/period). Files with the 'COM' extension can be run independently, simply type the name (e.g., DEBUG) and press enter and the command will be loaded from disk and will run. Other files will need to be loaded by another program and cannot run on their own.

As mentioned earlier, DEBUG is one of the available commands, which is a very handy program for looking at and (temporary) changing the internal workings of the computer. In the image that follows I have started DEBUG and used the 'D' command, which shows a hex dump, defaulting to hex address 100:

There was an 'Einstein' version of BBC BASIC which ran under Xtal DOS, designed to be very compatible with the original BBC BASIC, with the differences in hardware between the BBC and Einstein causing some differences. You can see in the next image that BBC BASIC is launched using the BBCBASIC command, and once it runs you get a startup message and you're dropped into BBC BASIC.

As seen in the screenshot above, a number of BBC BASIC programs, which have '.BBC' extension, are included on the BBC BASIC disk. They can be loaded in the normal way from within BBC BASIC using the load command, for example, to load the SORT program use:

LOAD "SORT"

Part of the beginning of the SORT program can be viewed in the following image:

Notice that this particular program contains Z80 assembly language instructions, one of the differences between BBC BASIC for the BBC Micro - which permitted 6502 instructions within a BASIC program - whereas the Einstein version allows Z80 instructions instead.

In the next screenshot you can see toward the bottom of the screen the results of running the SORT program:

Technical

Internally the computer was designed to be modular, and can be split into a number of sections; the main board, keyboard, Switch-Mode Power supply, and disk drive(s). The standard internal disk drive is a TEAC FD30A, single sided, 100 TPI, 40 tracks, MFM, 250 Kbps, 10 sectors/track, 512 bytes/sector. Disks used with the drive are 400KB formatted (200KB/side), the disk has to flipped over to access the other side.

I/O

Analogue to Digital Converter : 4 Channels, 8 bit resolution, 40uS conversion speed, 2V input range.

RS232-C Port : RS232-C/V24 standard, full duplex, software programmable between 75 and 9600 baud.

Sound Output : 250mW internal, 3.5 x 2.25 inch, elliptical loudspeaker. Three voice sound generator.

User Port : 8 bit bi-directional with strobe and ready signals TTL levels.

Tatung 'Pipe' : Z80A buffered bus, TTL Levels, with clock and control signals.

Pinouts

The Pinouts have been taken from the hardware manual, please double-check all wiring before powering the computer and anything you connect to it.

>Analogue 1 (M014)

1 Channel 0

2 Signal ground

3 Channel 1

4 /Fire 1

5 Vref

6 0V

7 +5V

>Analogue 2 (M015)

1 Channel 2

2 Signal ground

3 Channel 3

4 /Fire 2

5 Vref

6 0V

7 +5V

>RS232-C (M013)

1 0V

2 CTS (clear to send, to computer)

3 TxD (transmit data, to DCE)

4 RTS (request to send, to DCE)

5 RxD (receiver data, to computer)

Note: DCE=Data Communication Equipment

>User I/O (M002)

1 5V 9 0V

2 D0 10 D4

3 0V 11 /STB

4 D1 12 D5

5 RDY 13 0V

6 D2 14 D6

7 0V 15 5V

8 D3 16 D7

>Printer (M001)

1 /STROBE 18 0V

2 0V         19 /ACK (Acknowledge)

3 D1        20 0V

4 0V         21 BUSY

5 D2         22 0V

6 0V         23 PE (Paper End)

7 D3         24 0V

8 0V         25 N/C

9 D4         26 N/C

10 0V         27 N/C

11 D5         28 /ERROR

12 0V         29 N/C

13 D6         30 N/C

14 0V         31 0V

15 D7         32 N/C

16 0V         33 0V

17 D8         34 N/C

>Tatung 'Pipe' (M003)

1 +5V 31 A2

2 D7 32 A1

3 +5V 33 A0

4 D6 34 /RST

5 0V 35 0V

6 D5 36 /RFSH

7 0V 37 0V

8 D4 38 /M1

9 0V 39 0V

10 D3 40 /BUSACK

11 0V 41 0V

12 D2 42 /WR

13 0V 43 0V

14 D1 44 /RD

15 0V 45 0V

16 D0 46 /IORQ

17 0V 47 0V

18 A15 48 /MREQ

19 A14 49 0V

20 A13 50 /HALT

21 A12 51 0V

22 A11 52 /NMI

23 A10 53 0V

24 A9 54 /INT

25 A8 55 0V

26 A7 56 /WAIT

27 A6 57 0V

28 A5 58 /BUSREQ

29 A4 59 0V

30 A3 60 SYS CLK (4MHz)

>External disk drive (M004)

1 0V 18 /DIR-S (direction select, to drive)

2 N/C 19 0V

3 0V 20 /STEP (to drive)

4 N/C 21 0V

5 0V 22 /WRITE DATA (to drive)

6 /DS-3 (drive select, to drive) 23 0V

7 0V 24 /WRITE GATE (to drive)

8 /INDEX (to computer) 25 0V

9 0V 26 /TRACK 0 (to computer)

10 /DS-0 (drive select, to drive) 27 0V

11 0V 28 /WRITE PROTECT (to computer)

12 /DS-1 (drive select, to drive) 29 0V

13 0V 30 /READ DATA (to computer)

14 /DS-2 (drive select, to drive) 31 0V

15 0V 32 /SIDE-SELECT (to drive)

16 /MOTOR ON (to drive) 33 0V

17 0V 34 N/C

>RGB/YUV (M016)

1 R (V)

2 G (Y+syncs)

3 B (U)

4 Syncs (0V)

5 0V (0V)

6 N/C (N/C)

Power supply

Switch mode, 220V to 240V, 50 to 60Hz, 1A fused 5V outputs with overvoltage and short circuit protection.

Video

Display format: raster, 625 lines, 50Hz, non-interlaced.

Troubleshooting

Disk drive

Since the TC-01 features at least one built-in disk drive it will likely need servicing, with the belt drive possibly needing replacing, alternatively a floppy drive emulator - such as a GoTek - can be installed instead. For further information, please see my page on the GoTek.

Video

By default the computer outputs YUV but can be configured to output RGB by changing links on the motherboard - see page A.1. of the hardware manual, linked in the Resources section.

All content of this and related pages is copyright (c) James S. 2023-2025