Spectravideo.org Downloads?

Por jmetal88

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22-07-2016, 02:10

Does anyone have access to the downloads on Spectravideo.org? I've tried e-mailing the address listed on the site, but it came back as undeliverable. All the downloads give me a 301 redirect back to the home page. None of them seem to appear on Archive.org. I was specifically interested in the C.U.C. Universal Cassette Interface PDF and the downloads for SVITAPE and SVIPC. Thanks!

I also posted to the forum over there, but it doesn't look very active so I'm not sure if anyone will read my post.

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Por jmetal88

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22-07-2016, 14:31

Hmm, well, I found a schematic for the actual tape drive, so I may be able to design a circuit to accomplish the equivalent of the Universal Cassette Interface based on it: http://msx.hansotten.com/uploads/msxdocs/STM-E_SVI903-904.pdf

Being able to use SVITAPE and SVIPC would still be neat, but if I can't find them then I'd at least be able to use my sound card and the SVITOOLS package off Sourceforge.

Por jltursan

Prophet (2502)

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22-07-2016, 20:43

Welcome jmetal88!

Maybe you can find the source of the interface PDF, it's the C.U.C. magazine #18 and was designed by Peter Zevenhoven.
About the software, seems that indeed has vanished from the net. You can try to email the programmer, here's his page: http://home.arcor.de/b.arenfeld/Elektronik/elektronik.html

Por jmetal88

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23-07-2016, 00:59

jltursan wrote:

Welcome jmetal88!

Maybe you can find the source of the interface PDF, it's the C.U.C. magazine #18 and was designed by Peter Zevenhoven.
About the software, seems that indeed has vanished from the net. You can try to email the programmer, here's his page: http://home.arcor.de/b.arenfeld/Elektronik/elektronik.html

Ah, that's cool that you found his website. I had been looking and hadn't ran across it yet.

I've been looking for "C.U.C Magazine" as well and haven't been able to find anything. But I think I have a good grasp of what's going on in the cassette recorder schematics and should be able to devise a solution that will work (it looks like it's simply amplifying the tape signal to the point of clipping, then using a resistor voltage divider to scale the signal down from 0-12V to 0-4V (approximately). Which makes sense, since the input on the SV-318 is TTL, being that the lines are directly connected to the 8255. Making it work for recording will either be a lot simpler or a lot more difficult than what's showing in the schematic... I'm not sure yet, and it will probably take some experimentation on my part.

Por jmetal88

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24-07-2016, 15:56

Whoops, I calculated the voltage divider in reverse, it should actually be putting out around 8V peak if they are driving the amplifier to clipping as I suspect.

Por jmetal88

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24-07-2016, 16:01

I guess I need to get my oscilloscope on it... 8V should be too high for the 8255, so maybe they're not actually driving the amplifier to clipping.

Por jmetal88

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21-08-2016, 00:19

Hey! I got a successful tape read!

So the divider thing... I forget sometimes that most op amps aren't 'rail-to-rail', so that voltage divider is actually correct and will put out a maximum of ~6V, which should be safe for the 8255. Anyway, trying to duplicate the circuit in the tape drive schematic didn't work out for me, but what did work out was building a comparator circuit. I figured out that's essentially what the circuit in the tape drive is doing anyway, it's just that they didn't go quite as far as to make it 'open loop'.

I may tweak it some more before releasing the schematic. For now I only know that it works on one particular tape recorder, playing back at maximum volume.

Por jltursan

Prophet (2502)

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21-08-2016, 13:34

Good to hear that you're progressing!.

Never thought about that; but isn't the SVI tape design very close to the C64 one?, only for this machine there're about half a dozen different gadgets to play a digital signal. Maybe you can borrow ideas from some of them...

Por jmetal88

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21-08-2016, 17:03

It seems to be. I did look at a C64 tape adapter circuit, but what I ended up coming up with for the SVI was much simpler (and I've got it working on a much lower volume output now than I did originally with some decoupling and re-biasing of the input signal). Now I need to add a circuit to activate the REMOTE line so I don't have to manually pause the tape recorder between loads, and after that figure out a recording output circuit.

Por jmetal88

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24-08-2016, 14:22

Oh, and to get back to the original subject of the post, I notice that Spectravideo.org is completely down now. Sad
I guess we're on our own now to gather together whatever info may have been needed from that site.

I might look into reconstructing a parallel port interface myself as well, now that I understand how the tape interface is supposed to work. It should be fairly simple (could even be directly wired) but will just require some precise timing on the PC's part and will take some work for me to figure out exactly what that timing is. But since I have the cassette recorder interface working, I'm not promising any work will actually get done on that front, since output through the sound card is a pretty viable option now. I've ordered some additional parts for a 'final' version of the interface (one using more consistent non-junk-drawer parts) and will post the schematic once I'm sure it works at least as well as the interface I currently have put together on a breadboard.