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ZX81 Tape loading woes Pt 2.

falter

falter

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So I finally invested in a tape recorder -- a TRS-80 one.. one of those ones on offer on ebay for $12. Seems to work competently. Anyway, with the added volume my ZX81 definitely reacts differently, but we're still not getting victory. I discovered with the volume too high the ZX81 would bomb out of the load and just go to a solid grey screen. Too low, it just does the wavy dance endlessly. When I adjusted the tape recorder to volume around 2 or 3, what I get now is the normal wavy lines, and then the screen either drops back to the command prompt, or it goes solid grey, but never does anything more. Thoughts? I've verified these are basic 1K games (Breakout was one I tried).. this ZX81 is a 'US' model and has no expanded RAM.. also, I am running it off composite via a mod the previous owner did, if that makes any difference.
 
Come to think of it.. I was doing some reading on the zx81.. and realized the ula chip handled cassette functions. I replaced the ULA on my zx81 with one that brightens the video.. could that be a source of problems?
 
Okay so I decided to try a few things. First, I replaced the updated Ferranti chip with the original the ZX81 had and tried loading. No difference. If the volume is below a certain level the ZX81 doesn't react. If it goes above that level the computer reacts (waves on screen change) but then it drops within about 2 seconds to the regular prompt (trying to run the program does nothing). So then I decided to try it on my ZX80 and TS 1000. The ZX80 doesn't react at all and doesn't load anything. The TS1000 reacts a tiny bit (waves on screen change slightly) but never loads anything.

Pretty sure it can't be this hard. I'm watching videos of people playing wav files off their ipods/phones and the computer loads just fine. Just not sure where to go here.
 
Sounds like you have a noisy signal. Do you have an oscilloscope that can test output from the tape recorder?
 
Two quick things: make sure you don't have the MIC and EAR connections mixed up. And it's best to leave the unused connection (the computer's output to the tape deck for saving data) unplugged while loading data, otherwise having both connected could cause interference which might cause the loading process to fail.
 
The ZX81 (and the ZX80 even more) are quite picky on the signal strength, not all cassetterecorders manage the level needed for reliable (if that is ever possible) operation.

With the correct volume the bars/lines are about 50% black/50% white.

Have you tried saving a small program from the ZX81 to the cassetterecorder, preferably on a blank tape? See if it can handle loading back that recording.

Also check if the tape speed is constant, listen to a steady tone and if it varies a lot then that will cause problems too..
 
Thanks guys. Yeah the ZX81 connections are a bit confusing, but my understanding was 'EAR' goes to the EAR port on the tape recorder, which is why they labelled it that way. I think before I had tried doing MIC on the ZX81 to EAR on the recorder. I have also tried with the MIC connection disconnected. And there is definitely a difference in reaction depending on where I put the volume, so something is getting through. I'm kind of suspicious of these cables. I don't have any mono cables except these.. they came with this ZX81 and the ends on the tape recorder end were tarnished quite a bit. I polished them up, and definitely in using them to record from wav to tape it's putting signal on there. Kind of wish I had a real ZX81 tape to test with, I'm not fully trusting these wav conversions.

I could also be using the wrong programs -- I noticed some of the 1K ones I was trying to load were 'hi-res'.. don't know if that makes a difference.

I did try saving a program and reloading but no dice. I should check again to see if it's actually outputting any signal to the tape.
 
My recollection, from when I ran a ZX81, was that the volume should be at half when recording, and then turned up to full (or perhaps 90%) when playing back. 'Finicky' was certainly the word for it.
 
Okay. So I took the two cables I have for EAR and MIC and reversed them on both sides. I then tried to load a program I had recorded from WAV to tape:

https://www.youtube.com/watch?v=FyhJQthYfO4

By the counter on the tape, I've verified that it drops to that prompt where the program sound ends. It's in a 'free keyboard' mode where I can type whatever I want. If I try RUN, it just goes back to the regular mode. And then if you watch about 30 sec or so, it eventually goes to a solid grey screen all on its own.

To experiment again, I made a small program, saved to tape, and then played it back. This time, it loaded the program correctly. So it's obviously capable of reading properly (and saving). There is something about the programs I'm taking down from online that it doesn't seem to jive with.
 
Just a small question: do you have a rampack attached to the ZX81 ? If not then you can only load small (1k on a ZX81, 2k on a Timex 1000) programs, most games and other programs expect a 16k expansion.
 
No, no rampack. That was what I thought was blowing me up before.. I tried loading 3dmaze, etc.. which are 16k only. But I've been going to sites like this one:

http://www.zx81stuff.org.uk/zx81/tape/Ten1KGames

And trying 1K games from there with no success. I'm almost wondering if I have a RAM problem or something else. Seems odd that it'll load and then go a prompt and *THEN* freeze up almost a minute afterwards.
 
Is this the only tape recorder you've got? Have you tried loading from another? Or getting the program file to audacity or somesuch audio software and loaded from there? Also have you cleaned the heads of the tape recorder? A few suggestions but you've probably already tried them...
 
Yes this is the only one. I did try loading directly from my laptop and desktop but to no avail.. think the volume isn't loud enough.
 
One other thing I'm wondering about.. the wav files i'm generating from these tzx files I find online.. they all tend to be around 17-20 seconds long as a wav... I realize these are only 1k programs but doesn't that seem a bit short?
 
The ZX-81 does about 30 bytes per second on tape so your files would be around 500 to 600 bytes. Seems about right.
 
How exactly are you making the .WAV files into tape recordings?

-From what output on the computer, and in which mode is the output operating? (Headphone out? Line out?)

-Into which input on the tape recorder? (Microphone input? Line input?)

-Is the tape recorder mono or stereo?

-What type of plug does the cable have on each end?
 
What I've been doing is using Tape2Wav and converting tzx files to WAV. Then I use a mono cable with the mini-jack/phono (3.5mm?) plugs (same as regular earphone) going from the soundcard out to the tape player MIC port). I start the recorder, then hit play in Windows Media Player. I've tried switching modes from headphone to line out with no difference. This is a TRS-80 tape recorder like this: http://www.trs-80.com/images/hw-storage-ccr81x250.png

It has EAR, AUX, REM and MIC ports on the side. I believe it's mono, not stereo.
 
A TRS-80 tape recorder should not be stereo anyway, IIRC, so that's not an issue.
 
The sound card will most likely be STEREO with the recorder MONO. In this case I would use either the left or right output from the sound card - and not both - to record onto the tape deck. If you use both - you risk mixing the two channels (left and right) together and the frequency response may suffer.

The sound card will probably have a tip-ring-sleeve (TRS) connector. Inserting a mono (tip-sleeve TS) connector will invariably 'mix' the left and right channels of the sound card together.

You will also have to match the signal levels - so feeding a line output signal into a mic input socket will invariably result in distortion as things clip and you will change the perceived 'tones'. Going the other way (low level output to line input) will cause the volume level to suffer.

Just a thought...

Dave
 
falter said:
What I've been doing is using Tape2Wav and converting tzx files to WAV. Then I use a mono cable with the mini-jack/phono (3.5mm?) plugs (same as regular earphone) going from the soundcard out to the tape player MIC port). I start the recorder, then hit play in Windows Media Player. I've tried switching modes from headphone to line out with no difference. This is a TRS-80 tape recorder like this: http://www.trs-80.com/images/hw-storage-ccr81x250.png

It has EAR, AUX, REM and MIC ports on the side. I believe it's mono, not stereo.
Click to expand...

A tape recorder made for a computer (TRS-80) was always likely to be mono, but I thought I'd better ask.

If you use a headphone output either in 'Headphone' or 'Line Out' mode to drive a microphone input directly you have a serious mismatch in levels - the MIC input on a recorder is expecting just a few millivolts from a real microphone, so the ZX81 outputs a similar, tiny signal from its MIC connector. The output from the PC is huge by comparison.

Since the recorder has a 'Line In' socket (sometimes called AUX IN) then using that input (rather than the microphone input) in conjunction with the PC with its output mode set to 'Line Out' would be the correct way to go.

If the recorder didn't have a 'Line In / Aux In' input then you could try making this little level reducer circuit (see image - I kept it small so the forum wouldn't reject it - click on it to see a hopefully more readable version). This will reduce the 'big' output from the PC to the much smaller level expected by the microphone input on the recorder.

Note the use of a stereo plug at the PC end and a mono plug at the ZX81 end. Plugging a mono plug into the stereo output of a PC will short one of its outputs directly to ground, which is undesirable and may upset the audio amplifier or eventually even damage the output in question.

PC_output_to_recorder_input.jpg

The resistor values chosen are pretty arbitrary, the preset (variable resistor) will need to be set quite close to the 'low' end (but not all the way off!) for best results.

For your own setup I would try the PC in Line Output mode and connect it to the Aux In, not Microphone in, of your recorder. I would still make up a lead with a stereo plug at the PC end, for the reason stated above, but it won't need the level reducer resistors.
 
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