Dead or Alive?

[TheNeil]

Hi Guys,

I recently pulled a TC-01 out of the loft due to moving house and (finally) got around to plugging it in. I don't know anything about these machines (it was bought on a whim about 10 years ago) but...I'm at a complete loss (and why I joined the forum as I don't like consigning old tech to the bin).

Power light comes on, Alpha-Lock light comes on but no beep(s) and the TV output just shows black (but it's definitely putting out something as, when powered off, I get static - TV and cable are both fine BTW as they happily work with several other non-Tatung machines). Pressing keys on the (gunged to hell) keyboard doesn't have any effect, the disk drive doesn't spin up (even with a disk in it) and although hitting the reset button appears to cycle the power (the black output 'ripples' ever so slightly) there doesn't appear to be any sign of it getting any further.

I've reseated all of the socketed chips (no effect), reseated keyboard and floppy drive (no effect) and a visual inspection doesn't show any board damage or capacitor leakage.

Any ideas on what I need/should try next? Is it terminal?

[MikeDHalliday]

Your TV is definately tuned in to the correct channel?

Could be a dead VDP driver chip. These are fairly easy to desolder and add a socket, depending on how competent you are with the old solder iron? How easy they are to find online though is another question. I have not looked for one for a while.

Does your machine have the 80 col card attached? If so, use a composite cable and connect it to a composite monitor to see if you get a picture there?

I am sure someone on the forum can help you if they are close by?

I can have a look at it for you (I have fixed a few in the past), but you would have to send it via UPS to me! Send me a PM if interested?

[TheNeil]

Hi Mike,

I set the TV to scan and it was the only signal it locked on to so I'm 99% sure it's done the best it can (it manages to pick up Ataris, Acorns etc.) - the fact that there was nothing else (beeps, drive spinning etc.) made me think that the problem was something else. I have tried it again though and same result.

I don't believe my machine has an 80-col card fitted - only things plugged into the main board are the (single) floppy drive, the keyboard, the power and the speaker.

Soldering isn't my strongest skill but I can do it at a push (although I may take you up on the offer of shipping it to you - I'm in central Wales so not near anything). I think I know which chips are involved (the two just up from resistor C047) but can you confirm which one(s) I need to go hunting for?

[TheNeil]

Sorry, I think I was looking at the wrong chip(s). Is it the TMS 9129NL (at the bottom of the board next to the speaker)?

Having done a search, they're about £40+ and not exactly easy to get hold of. I hate to ask but are there alternatives that can be used?

[MikeDHalliday]

No alternatives that i know of, or can find searching online.

Ali Express looks to have cheap ones in, if you are willing to risk a potential knock off?

https://www.aliexpress.com/item/4001034991999.html

£26.04 with £2.35 shipping to UK.

Never tried one so it could be a bust, or it could be the saviour of old computers?

[TheNeil]

Thanks Mike - replacing individual chips is a little outside of my comfort zone so thanks for confirming.

I'll see about getting one ordered and the look to get it fitted (although, as I'm a coward, I might it and send you a PM about the actual soldering )

[Lardo Boffin]

The 80 column card sits on the back of the Tatung, outside the case in a little case of its own so should be fairly easy to spot!