When we last left off, I had found, to my great excitement, some actual vintage 1973 PCB copper clad stock. And I was delighted; this gave me the opportunity to go the ‘last mile’ in authenticity. It meant my TV Typewriter would be composed approximately 95% of vintage parts!
Of course, this presented a problem. Since I had gone ahead and built my TVT with the new board stock, it would mean (ugh) taking it all apart and redoing it on new boards. I really wasn’t keen on starting over again. It was really tempting to just finish it off and carry on. But events forced my hand.
The first was my acquisition of a vintage, original TV Typewriter construction booklet!! This was the guide Radio Electronics would mail you for a fiver. It had a reprint of the original article, as well as schematics and, crucially, the full size PCB layouts!
It’s quite amazing to have one of these in my hands!
You’ll recall to create my TVT boards I had relied on scans of the plans on SWTPC.com. These were very useful, but unfortunately the scan quality was not great. And these were afflicted with another problem: scanner distortion. The original artwork was printed at full size in the construction guide, and since the writers didn’t expect as yet unborn children to be relying on scanned copies, there was no scale provided. I did my best to scale it up, measuring against actual ICs. I figured if I got the IC pad spacings right, the rest would fall into place. I was wrong. I had noticed as I built that some things seemed a little cramped. But again, with only photos or scans to rely on, I had no way of being sure my dimensions were out. However, now with the originals guide in hand I could compare.
I had thought I’d be out by maybe a quarter inch or less. In fact, I was out by a full half inch all the way around. This was confirmed by the arrival of my brand new one-off Signal 24-1A transformer, which Signal Transformer themselves had resurrected for me. Looks pretty sharp, eh?
Buuut… it doesn’t fit. The transformer actually cuts into the area where the three other boards plug in. Ugh.
Another thing which I had neglected to do was read the instructions. For this, I had no excuse – they were there in black and white in the scans on SWTPC.com. The manual warned specifically to proceed in stages, but as I was a bit too eager to get going, I had built the boards completely out of order and simply as parts arrived. This was a mistake. The order of construction is just as important as anything else; by proceeding in a specific order one step at a time, you are able to isolate potential problems as you go. This is invaluable.
Thus the decision is made: I must re-do. De-soldering will be painful, but a valuable lesson has been learned. And anyway, I can at least get that last squeeze of authenticity out.