A couple of times in this forum I've mentioned a "Scrubber-Dubber" that I built from a magazine article in 1983 or so. The article was called "Improving Timex/Sinclair Tape Loading" by Tim Stoner, and appeared in the September 1983 issue of "Computers & Electronics". Up until now, all I've had was a very poor 1983-technology photocopy of the article, with a hand-drawn copy of the circuit diagram and parts list, because the magazine chose to publish that part of the article as black on gray. (Grrrr.)
Time, effort, luck, and a few PayPal dollars have finally come together to allow me to obtain a better scan and electronic copy of this article. I offer it here to anyone who is interested in building the circuit. Tim, if you're out there and object to this, let me know and I'll take it down. Otherwise, thanks a million for this great device, which has let me read and LOAD programs otherwise deemed to be irretrievable from problem tapes over the years.
Short summary: The device uses a quad op amp to read and clean up a waveform between the tape player and the ZX81. It also provides a slave recorder "mic" output, so that you can make a clean copy of the original tape at the same time as the ZX81 LOADs, or without the computer entirely. (This was useful for cloning CHESS-CLOCK, which I never succeeded in cracking as I had CHESS from Side 1. Shhh,...) It works brilliantly.
Surely we all have .p files of our favorite programs by now, but just in case you've kept that one cassette with your Masters Thesis that you never could quite get to LOAD cleanly, building this little toy might be your ticket.
- Improving ZX81 Loading.pdf
- (4.41 MiB) Downloaded 541 times
One of them had a crazy but in it preventing it to be loaded even on a true ZX81 machine: in place of the gap between two bits it had a continous frequency, if I remember correctly it was one extra oscillation.
Cleaning the wave file but flattening it made the conversion possible but I couldn't explain that ..the square wave was perfect and clean but wrong !
My assumption was that one of these boxes did a bad joke: opinions ?
I just saw this post and would like to build one of these - I have some tapes that may benefit from it!
Any chance you can post a few photos of the inside of yours please? As a newbie to building stuff I find it a lot easier with an actual example to look at for reference.
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
The carbon resistors (and probably the wire wound ones too) were salvages from old TV sets I used to raid for parts. Note that in two cases I couldn't find the right value, and approximated it by substituting two resistors in series.
The trace side is an embarrassment. It was my first, and I think only, attempt at etching a circuit board. Messy business. If I had to do it over again I might use prototyping board and suffer with making all the connections. Then again, there are probably easier ways to get a circuit board made from an image by now--I haven't had occasion to repeat the exercise.
But it works, and has rescued many a tape. Best of luck building yours!
- Full Rez.zip
- The photos at higher resolution.
- (4.94 MiB) Downloaded 212 times
- Trace Side (600 x 450).jpg (80.78 KiB) Viewed 6388 times
- Component Side 2 (600 x 450).jpg (69.18 KiB) Viewed 6388 times
i think i will look for some proto board and try to build the box, i save from the dust some of my old tapes and i think it can help reading them on my Zeddy