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ZX Spectrum 48K Repair. I could really use some help from the other side of the pond repairing this...

I would (personally) use a cable like this: https://www.amazon.co.uk/kenable-3-5mm-Stereo-Plugs-Audio-Black/dp/B00E8EQXF0?th=1.

Note that the Amazon description is plain wrong. These are not HDMI connectors!

The stereo end plugs into the source (iPad, phone etc.). The mono end plugs then give you the right (red) and left (white) channels.

Try both the red and white mono connectors with the Spectrum and see if one is better than the other.

If this doesn't work - you are looking at signal levels and/or tone - and that will not be solved by the cable you are using.

Dave
 
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Probably worth while. I've not had issues with my USB adapter but a proper stereo to separate jacks removes the issue (well, as long as you use the one with the noise coming out of it I suppose)
 
>>> Try both the red and white mono connectors with the Spectrum and see if one is better than the other.

:)

Dave
 
This really seems over cautious
Click to expand...

Sorry, I should clarify: The need to run from batteries or an isolated supply only applies if you choose to use the antiphased-output method I described because if you use that method there must not be an unintended connection between the source GND and the computer GND, otherwise that will short one of the two antiphased outputs to source GND.

If you are using one stereo output channel + GND as you conventionally would then there is (probably) no need to worry about an unintentional extra ground connection through the power supply / video wiring / mains wiring.

And to stress, it would only be necessary to try the antiphased output method if the maximum audio output voltage from one output channel of your source was not loud enough for the computer to be able to 'hear' it. The MP3 player I mentioned ran on a single 1.5V AAA cell, and was not able to generate enough output voltage from one channel. I have a small Dell 1011 netbook: The audio output from one channel on that loads my ZX81 just fine, but I wanted to be able to load the ZX81 up with something I could just carry around in my pocket.
 
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So I bought the cable absolutely no difference. I checked the outputs from my computer. ITs a mono file I am playing and it is just playing the same exat thing out both channels. So with the splitter I just received I am still getting the same signal I can just choose between right or left channel now.

Could it be because I am running this on 60Hz North American power and its a PAL UK machine? Screwing up the timing? Just a thought.

I spent another few hours. Its the same thing. I can get the ZX spectrum to display the name of the tap file I am playing and if I adjust volume or tone The spelling of the file will change (get corrupted) and it will change the error.. Or more often then not reset the spectrum.

This is beating a dead horse. I Think I am just going to try burning a Diagnostic ROM. I have a few 27128A Intel Eproms I could use and I just ordered some schotky diodes.
 
I think the cassette data timing / frequencies are the same regardless of the nation setting. By the time the supply voltage gets to the Spectrum it is full-wave rectified and smoothed low voltage DC, so that question is almost irrelevant - although any ripple present on the unregulated DC input from the power supply will be 120Hz, rather than 100Hz - this is unimportant.

Can I ask where you obtained / how you created the file you are trying to play into the Spectrum?

Some suggestions:

-Find some more Spectrum audio files online and try playing those in using the same method.

-If you actually have a cassette tape recorder try typing in a three or four line BASIC program, make sure it works, save it out to tape and then try loading it back in.

-You can also use a PC as a 'Tape Recorder' for this purpose but there it gets a bit more complicated as the 'Mic In' terminal on a PC normally provides phantom power for an electret microphone down the mic signal line. If connecting the mic-in of a PC to a ZX computer mic-out if might be wise to put a blocking capacitor in series with the audio signal. Edit: Actually looking at the diagram posted earlier there is already a series capacitor in the MIC-OUT circuit so belay that last observation.

You can use a 'technical' sound recording application like Audacity or a simple utility like the 'Voice Recorder' App built into Windows.

Could you post the file you are trying to load here as an attachment? I don't imagine the forum will allow files with a .TAP extension but if you put it into a .ZIP file you will probably be able to attach that. I'm sure there are a few of us here who can try loading the file on our systems.
 
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OK Verault - it's quite late here in the UK but I will get my 1982 Spectrum down tomorrow evening and try to load this file. Maybe others can have a go at it as well. What software do you use to 'Play' the file on the PC? Is it Linux or Windows (I can do either).
 
VERAULT said:
Thank you, but I fully expect that it will work for you just fine.
Click to expand...

Should I do it then? My main aim was to try to replicate what you were doing, to see if it worked for me but you seem to feel there isn't much point. Would you rather go the diagnostic EPROM route instead? Let me know.
 
Sorry, I missed that you said that earlier. I haven't actually heard of the OTLA software before, I've just grabbed the Windows binary. If it will run under XP I have a little netbook which should be the ideal platform. I have to go out for an hour or two but will see what I can do later. My Spectrum hasn't been on for a few years so let's hope mine still works.
 
Neither had I. I mentioned I found this video on post #115
and since programs that play tap files on android dont typically exist for windows I had noting else in mind and gave it a try. Seems a pretty good program with many options after giving it a go.
 
I have OTLA running but I have run into a bit of a brick wall as I expected just to be able to load files with .TAP extensions and play them out as audio, but on first look it seems that it will only let me load files of .SBB format, whatever that is. There is a drop-down file type selector in the 'Open File' dialogue but I can't change it from .SBB to anything else or even to 'all files'. I think I'm going to have to watch the video before I can proceed.
 
Isn't OTLA a speedloader ?

What happens if you just play a WAV version of a TAP file into the Spectrum ? That surely is the simplest test.
 
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