Tatung Einstein Restoration

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​Recently acquired a Tatung Einstein computer
Purchased 4th July 2024
Unpacked, looks in good condition though some keys (>12) not working or working intermittently.


​The cardboard boxes and polys need a fair bit of attention.
​BOOKS
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3 manuals, all pretty shabby, dirty and creased, also the binding wires were rusty.
They had all had serious water damage so they were all stripped.
Each page was:
treated for water damage by trying to soak out some of the stains, then ironed.
The covers were strengthened where necessary with new binding wires fitted.
MONITOR

Opened and inspected, all very clean, no RIFAs and no sign of overheating.
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Did notice a few solder splashes on 2 resistors, removed the solder as I didn't want it coming loose at some point and shorting something.

Mains plus was the old BS1363 style so swapped for the 1363A type.
​BASE POWER SUPPLY

The mains cable was badly twisted and had poly damage, plus an old plug so I swapped the entire cable and plug for a modern one (1363A).

​​I actually plan to replace the power supply with a Meanwell PT65B, this has a higher rating that the original, however, I am going to recap the original and keep it with the unit so it can be restored to 'original' build if it ever gets anywhere near a museum.

​The power supply was recapped with Nichicon UBT capacitors, these have a higher temperature range up to 125°C and higher reliability. They were originally designed for the automotive industry so can withstand a bit more abuse (heat variation, etc.)
I did notice that CE23 was wedged between the heatsink (gets hot) and the transformer (also gets warm) so I used the leg length of the replacement to move it just outside hot zone.
​When it came to replace the large 100uF/400v monster I have a few choices to make.
I have 4 alternatives...
 an L.C.R. of exactly the same physical size, lugs, etc. from NOS, the issue being that this is a 1987 capacitor, though completely unused.
 A Nichicon (new)
 A Panasonic (new)
 A Cornell-Dubilier with a slightly higher voltage (450) (new)
It would in my mind look better with the L.C.R as it is more in keeping with the age, but the modern capacitors are very reliable, much smaller physically so may contribute to a better cooling of the very close heatsinks.

Finally chose the L.C.R. (it just looked better)
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​Also added spade terminals to the output connections so these can be moved over to a replacement PSU (Meanwell) to be fitted into the Einstein itself.

Tested back in the Einstein with no issues at all.
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PCB treated with silicone conformal coating.


​Meanwell unit fitted into original PSU case with a plastic riser plate and tested with the Einstein Base. All OK
BASE UNIT
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removed the main board for recapping.... noticed one of the fixing pillars in the base had a crack, a drop of MEK and a clamp fixed this [ein12]

​​The underside of the board looked good, it had 2 mod wires, I cleaned the old flux off and raised them up at the termination ends and put some UV resin underneath at the terminals to reduce the risk of a short where they crossed some very close tracks.[ein13]
​​I recapped the main board with Nichicon capacitors and then retested it, all good so far.
One final check on the main board showed a couple of ICs going above 50 degrees C, so heatsinks were installed, now all components sit well below 50.
Interestingly the LM340T5 was getting too hot for my liking so I removed it, as I did this the pin1 literally fell off as if fractured at the component end. Anyway I fitted a new one and upgraded the heatsink size.

Board retested with the diagnostic ROM, ATP.

Installed a FlexiDOS ROM because I had one, on the off chance I ever find a FlexiDOS disk image!
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​As an aside I often put all the fixings, screws, etc into a bag and flood it with WD40(silicone) as a rust protector.
KEYBOARD
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The keyboard needed a good clean.
Keycaps removed and put into the ultrasonic cleaner with a weak solution of UBIK2000 cleaner for 10 minutes, rinsed and looking great.
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​Time to strip the keyboard down, not just targeting the dodgy keys but decided to do all of them.

​​Initial testing showed 12 not working with some others unreliable.
​Keyswitches put through ultrasonic cleaner filled with IPA. On retest all but 4 tested fine (< 0.1 ohms)
These were completely stripped apart, cleaned, treated with DeOxit, contact leaf spring re-tensioned and reassembled, then tested OK.
What I discovered was that the 'contacts' are sandwiched between a mylar layer (top right of image) and it is very difficult to get any kind of contact cleaner in there without disassembly, this explains why my first attempt of recovering bad contact switches by spraying contact cleaner into the top of the assembled switch always failed, just not enough gets through to the actual contact itself. Thankfully de-soldering and stripping the keyswitch is very simple.
Keyboard then reassembled.
DISK DRIVES
Both drives looked clean, however the 'B' drive had 'lost' its shield (assuming it had one).

Fitted a GoTek as drive 0 and left the original drive 1 in place, made a new custom drive cable and practiced cable origami to make it look nicer.
However, the original drive 1 was a bit noisy so I re-jumpered the original drive 0 and swapped it, this is when I discovered that the ribbon cable was the opposite orientation, this explains why when I first got the machine the drive 1 was fitted upside down. A bit more cable origami and fitted it the right way up, I left the extra ribbon cable length in (I could have re-terminated it) in case anyone wanted to refit the original drive 1.
THE FUTURE

* Fit a ABBA drive switch to be able to swap the Gotek / 3" drives over.

* Build an external 2 drive bay using the original drive 1 and possible a DS 3.5 inch drive.