ZX81 Tape Woes...

[XorA]

Back in the day the best success was always the cheapest crappiest mono cassette player money could buy. Any feature beyond "none" just seemed to mean distort signal cause hassle!

[1024MAK]

You don't have to worry about damage to the keyboard tails/ribbons/flexiprint unless you unscrew the two screws that hold the PCB to the top half of the case.
Removing the bottom half of the case is okay.
And if your keyboard tails/ribbons/flexiprint do become damaged replacement membrane keyboards are available

@ gozzo - that's why I said "typically". But he is right that Sinclair / Timex used different boards and different components depending on supply and cost.

Issue number on solder mask near modulator for an issue 1 PCB

Issue on solder mask (Issue 1).JPG (101.44 KiB) Viewed 3549 times

Brown flux on mono 3.5mm jack pins

Brown flux on 3,5mm jack pins.JPG (81.88 KiB) Viewed 3547 times

Torn ribbon

Torn ribbon.JPG (54.26 KiB) Viewed 3547 times

Mark

[Rink]

Cheers Mark, I'll see what I can do without removing the pcb.

Pretty much exhausted all audio playing devices I can get my hands on - none of them have got even a twinge out of the ZX81. Hardly a scientific process but given how many people on the Internet seem to load tapes from mp3 players and PCs, it would seem that one of the many should have at least registered some kind of signal.

I need to check with my friend and see how far he wants me to go with this. He might prefer to send it off to someone more knolwedgeable (and with better gear) if an actual repair is necessary. I'll just check the socket again, see if there's anything obviously wrong with the capacitor and resistor(s) in the filtering part and check continuity to the ULA. Not sure I could do much more than that - other than try to replace cap/resistors if that looked like it might help and he was happy for me to do that.

[angus]

I find the best way is to use a cassette player/recorder. I've tried my phone, laptop and so on playing MP3 and WAV files all to no avail. Even tried burning to CD and using a portable CD player.

The most reliable source seems to be a cassette recorder. Currently I am using a handheld (walkman sized) mono cassette recorder by Sanyo that I picked up dirt cheap on eBay about 9 years ago.

It might just be a case of volume and 'oomph' but there is something to be said for the lack of electronic processing inherent in a basic cassette recorder. Back in the day everyone (including myself) got better results from a cheapo-crap "shoebox" cassette recorder than a hi-fi deck. It was also often the case that cheap cassettes worked better than more expensive ones. Really you just need a fairly steady speed and relatively flat frequency response in the same frequencies used for speech.

If you are processing signals, try rolling off everything below 100Hz, possibly even 150Hz. That might help.

[Andy Rea]

i wouldn't apply any equalization, when i used my mp3 player i have to have it all the EQ FLAT and volume at MAX.

Andy

[Rink]

Don't suppose anyone out there has a working tape player and an oscilloscope? I'm using an arduino as a basic scope - which kinda works and indicates that my PC is putting out an audio signal up to about 1.2v (so well below ttl levels); I'm just wondering what kind of output others are using.

Next I'll be using it to help amplify the signal in the a more controlled manner and probe around inside and see what (if anything) is getting through to the ULA. Unfortunately a few too many beers last night is hampering my progress today.

[RetroTechie]

I'm using an arduino as a basic scope - which kinda works and indicates that my PC is putting out an audio signal up to about 1.2v (so well below ttl levels)

Don't worry about the "below TTL levels" part: there's some voltage range where logic level changes from 0 to 1 and vice versa. That 'gray area' is often no more than a few tenths of a volt, and the part of the audio signal that makes it up to the ULA pin, needs only be strong enough to make the logic level flip back & forth (not go 0-5V & back).

1.2Vpp is a decent audio voltage level, and a number of people have had success with MP3 players, which are much weaker in voltage terms (since geared to headphones). Where you have a choice: "line out" is preferred over "headphone out" for this purpose.

You can try to probe voltages, put a logic tester on the ULA pin, etc, but in the end the only (and simple) yard stick is the loading pattern you see - and if/how it changes as you crank up the volume. Btw: what cable(s) have you used so far?

[Rink]

You can try to probe voltages, put a logic tester on the ULA pin, etc, but in the end the only (and simple) yard stick is the loading pattern you see - and if/how it changes as you crank up the volume. Btw: what cable(s) have you used so far?

At the minute, it's still adamantly refusing to show any change in patterns.

I've tried loads of cables and adapters etc. and today verified that the signal at the end of them is the same as the one at the start. Everything from standard 3.5mm stereo to stereo cables, stereo to twin phonos and then a 3.5mm mono adapter on the end of one of the phonos, high quality instrument cables, and a few homemade creations. Nada.

Don't have time tonight to take it apart and "scope" around in there but there must be a problem in the box. Can't see any other option.

Cheers mate.

[Rink]

Actually... I might have made a schoolboy error here. Up until this point, I've assumed that WinTzx and the Breakout.p file I downloaded are valid.

Can you point me in the direction of a wav/mp3 I can download which definitely works? Just so I can cross that possibility off the list?

Thanks for all the help and advice so far. You guys have been great.

[sirmorris]

There are a number of 'P to WAV' type programs available that may be better for you. They are linked around the site; here is one such:

download/file.php?id=269

from this thread:

viewtopic.php?f=6&t=425&hilit=p2wav

Hope this can help in some small way.

C