Is it really Evil? Or is it just that things move to their lowest
energy state? After sitting unmolested on a shelf for a year or two, I discovered
that my Tascam Porta-Two would not play anymore. Right out of the blue. It would
turn on, but just wouldn't run tape.
Belts, you're thinking, right? No, the belts were fine, and all the turn-y things were turning properly. But it's a "soft-touch" play mechanism, and the metal platform
that moves the heads and idler wheel wasn't moving far enough. A distinct lack of engagement there.
I thought maybe I was lucky and there was something loose, or maybe a piece of something had fallen in the way of something else, I'll just have this open and have a look. I couldn't find anything like that, and tape-drive mechanisms just make my head hurt. So I went on the web.
Lo and behold, lots of folks have described exactly this problem! Some have even produced wonderful photos of the mechanical bits in question, and gone so far as tearing everything apart to investigate. We stand on the shoulders of giants, my friend...
So this one guy correctly determined that there is a spring that has sprung. Only, given the remaining evidence, he can't exactly figure out how to repair it. The plastic bracket
that holds the spring, the record head and the erase head has failed. In failing, it has basically exploded. I tried reconstructing it to what I assumed to be its original shape, (using sealing wax and brass wire, of course)
but compressing the spring to what seemed to be its working position (with that long arm sticking out the channel to the right) was more stress than my repair could take. It was really a lot of force, and it was puzzling...
Something was amiss. Wrapping that spring as tightly as seemed to be required was causing it to bind up on the post. That couldn't be right. I decided that the short arm of the spring must have been held in a less tightly coiled position somehow. Maybe when the bracket snapped some part of it disappeared.
I couldn't find any missing pieces. It was a conundrum, alright! But suddenly, looking at the bracket and spring stuck in place, I realised that I could drive a screw into the base metal slide part that would hold the spring in a less tightly coiled position. And I could locate that "tensioning screw" just about wherever I wanted it- there happened to be a slot under this area that provided clearance for any part of the screw that stuck out on the other side. Yippie-skippie!
I took a guess at a location and made my mark...
This shot also gives a good view of another feature. The long arm of the law (er, spring) sticks out to the right here. The bracket and the base metal sliding part are pushed forward by that milky-white, oil-stained post sticking up there. Without the spring pushing back against it, the post only moves the stuff part way, never engaging the drive or the heads. Hence, no play. (no repair is complete without a "hence" in there somewhere...)
Here we are again with the busted bracket removed. I've drilled a hole on my mark and I have a screw picked out to try. Brass seemed like the best material for the screw, because it will be right under the recording/playback head, and is non-magnetic. Unfortunately, this screw had too large a head, and I had to find another one.
Now the bracket and spring are in place. No pretty brass screws for this repair, I had to use a nasty, rusty screw. You can see how that spring broke right through the side of the bracket... or maybe it was held in this position by some lug or bulge or something.
Here the heads are in place. You can get an idea of the clearances involved. Even though it's tight, I think that screw is far enough away not to matter too much. It's only cassette tape, afterall...
But would this work? I had some luck earlier, pushing the bracket forward using a screwdriver. I fired 'er up and yeah! she ran. But did I mention that the motion of this metal base also presses a drive wheel against the take-up reel of the cassette? I didn't? Well, it does, and in this case, there wasn't enough pressure to consistantly engage that mechanism. I needed to tighten the spring somehow.
Good little monkey that I am, I saw this one coming, and that was part of my calculation when it came to locating this screw. I wanted it on the loose side, because it seemed easier to add tension than to release it. (just like in real life) I could re-drill the hole and use a larger diameter screw if all I wanted was a little more tension. But, being a lazy little monkey, the other option sprang to mind- add a shim!
That shiny aluminum piece is the shim, which I slid into place without having to disassemble the heads and bracket again. I just cut a piece of metal to shape and jammed it in there.
Here it is from the other side. You can easily see that the spring is under more tension with the shim in there. It works so far-I hope it stays!
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