ZX81 loading of programs not working

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repetto74
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ZX81 loading of programs not working

Post by repetto74 » Wed Dec 26, 2018 3:09 pm

Hi,

I tried to load a 1K P. file directly with a an audio player by connecting the ZX audio input to the audio output of the PC with a mono audio cable (I cannot recall if I have to use the EAR or MIC socket to load but tried with both with no luck).
After the LOAD "" I just get a weird scrambled screen which does not seem to look right compared to what I see on some youtube videos. I hit play to transfer the file but nothing happens after several minutes and keeps displaying the weird loading pattern. :?:
Is that a bad ULA signal or should I check somewhere else?

Thanks
Rick

https://youtu.be/ueyWvdk-8ZA
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mrtinb
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Re: ZX81 loading of programs not working

Post by mrtinb » Wed Dec 26, 2018 4:09 pm

If you have a cheap oscilloscope the voltage should shift between 0V and 5V.

If you only have a voltmeter it will show the average which is 2.5V.

Adjust the volume on your pc so it shows the voltage above.

If the volume/voltage is too low or high - the software would not load.

When you try a second or third time, remember to power off the ZX81 in between, so no corruption from previous load will influence the new load
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

repetto74
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Re: ZX81 loading of programs not working

Post by repetto74 » Wed Dec 26, 2018 6:03 pm

Hi mrtinb,

I have tried to found the 'sweet' volume level and I do see some loading happening (almost at 3/4 max volume level) but then I am back at the prompt K cursor and no program is listed in memory and RUN will just bring back a 0/0. If I go one notch up on the volume level then the ZX81 will crash immediately (no video output) and requires a power cycle. Any notch down on the volume will just let the loading screen sitting there and nothing happens.
There is definitely something wrong on the cassette port audio input circuitry somewhere. Hope this is not an ULA failure. :|

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mrtinb
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Re: ZX81 loading of programs not working

Post by mrtinb » Wed Dec 26, 2018 6:06 pm

Try with some other wave files as well. Make sure the wave file will load in EightyOne first.

Remember getting even fully functional software to load is an art.
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

dr beep
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Re: ZX81 loading of programs not working

Post by dr beep » Wed Dec 26, 2018 6:17 pm

A 1K file needs about 30 sec to load.

repetto74
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Re: ZX81 loading of programs not working

Post by repetto74 » Wed Dec 26, 2018 6:32 pm

Try with some other wave files as well. Make sure the wave file will load in EightyOne first.
I am using a program called TapeConverter which can also send data into the ZX81.

http://www.zx81stuff.org.uk/zx81/tapeut ... rview.html

The 1K file is a P. file type. I am using a mac not a PC but the program is a Java application which can be loaded fine. Last thing to try is maybe using this utility under Windows environment or try a Wav file (any source where to find those?).

Checked the p. file and another one picked randomly and both will load fine in EightyOne.

PS : should I use a mono to mono audio cable or is stereo/mono required?

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mrtinb
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Re: ZX81 loading of programs not working

Post by mrtinb » Wed Dec 26, 2018 7:06 pm

I have a Mac myself and I have not had any luck with them together with ZX81. Their audio port is combined input / output with 4 terminals like the iPhone. If you should have any luck then a stereo-to-mono cable would be best. The audio input is useless on the Mac when it comes to ZX81 output. This is because the ZX81 output is so low that the Mac audio input hardware cannot read it.
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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mrtinb
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Re: ZX81 loading of programs not working

Post by mrtinb » Wed Dec 26, 2018 7:13 pm

I gave up using the Mac with the ZX81.

I bought a ZXblast and later a ZXpand which uses a USB stick or an SD card. My last effort has been to build a TZXduino extension to my Arduino UNO controller. This uses a micro SD card.

All three devices uses the .P file which is much easier. Unfortunatly I have no hardware that can read cassette tapes. The portable mono cassette recorder I have, has too weak output for the ZX81.
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

repetto74
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Re: ZX81 loading of programs not working

Post by repetto74 » Wed Dec 26, 2018 7:43 pm

Hi have a TZXDuino which may work with the ZX81 unless I find some TZX files to test. I do not think it can handle the P. format. :x

repetto74
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Re: ZX81 loading of programs not working

Post by repetto74 » Wed Dec 26, 2018 8:08 pm

Ok so I found some TZX images for the ZX81 and tried to load them with the TZXDuino (working fine with TZX for ZX Spectrum) but I got an error on the TZXDuino display. Unfortunately I do not think this Duino is compatible with the TZX file format for the ZX81.
Last try is to load a wave from Windows but even if installed on the mac it will use anyway the mac hardware so I doubt. :|

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