Apologies, I had to take it offline.
I seldom update my Blog but I post plenty of shiny stuff on Twitter here:
https://twitter.com/RealJamHamster
In the meantime, and to counterbalance the bad news, here are some shiny things I’ve made during lockdown in no particular order:
Apologies, I had to take it offline.
I seldom update my Blog but I post plenty of shiny stuff on Twitter here:
https://twitter.com/RealJamHamster
In the meantime, and to counterbalance the bad news, here are even more shiny things I’ve made during lockdown in no particular order:
Apologies, I had to take it offline.
I seldom update my Blog but I post plenty of shiny stuff on Twitter here:
https://twitter.com/RealJamHamster
In the meantime, and to counterbalance the bad news, here are some more shiny things I’ve made during lockdown in no particular order:
If you want to use any of these images then please ask me first, feel free to hit me up on Twitter. 🙂
Apologies, I had to take it offline.
I seldom update my Blog but I post plenty of shiny stuff on Twitter here:
https://twitter.com/RealJamHamster
In the meantime, and to counterbalance the bad news, here are some shiny things I’ve made during lockdown in no particular order:
Shiny! If you want to use any of these images then please ask me first, feel free to hit me up on Twitter. 🙂
Whilst developing my TZXCassette, I noticed that certain games wouldn’t load despite them working fine when fed through the line in. There are a number of games (speedloaders etc.) that really dislike being loaded by a Cassette Adapter. As this is the way I plan to use the TZXCassette and there are a bunch of titles that don’t load, it’s a big problem.
I downloaded Soundcard Oscilloscope, plugged a lead and Cassette adapter into my Speccy and set to work. Having never used a scope before, it was a bit of a learning curve, I got this from the external port of the speccy and it’s a mess!
There was also evidence of harmonic distortion.
Thanks to some brilliant work from Duncan Edwards with a new TZXDuino firmware and advice from Keir Fraser I learned how the TZXDuino should work and what to expect. The TZXDuino is a wonderful device the TZXCassette uses as its internals and this works amazingly well but when someone does something stupid with it (like me!) then things start getting sticky (and not in the good way).
I whipped up a test setup and through more luck than judgement, made some slow progress.
To load successfully from a tape adapter you need a REALLY specific volume, I’m talking safecracker specific, and it needs to be really loud. Games loaded fine from the line in so I knew the kit was good, it was just that damned tape deck doing ‘something’. Have I mentioned that I have no clue what I’m doing yet? 🙂
After some more examination, I started to spot a pattern in the waveform that I was sure didn’t belong. There were dips in the tips of the waveforms.
This made no sense to me, at lower volumes these tips would intersect with the middle line and cause a ‘double peak’ and of course, a loading error. Through raising the volume you could ‘push’ the peaks into the right place but the edges of the waveform were ragged and sounded awful. It worked but didn’t seem right.
I did a bunch of reading to find out what the Spectrum was actually expecting, nearly everywhere said square wave, straight to the ULA. I found one sentence that made the whole problem come together.
‘ZX Spectrum Cassette tape waveforms have to be sinusoidal’
The supposition… Brace yourself for the science bit….
The ULA takes a square wave, the Datacorder wants a sinusoidal input, it’ll convert it to a square wave and move it to the ULA, all good. That is unless you feed a square wave into the Datacorder which many people have done and have been frustrated by as it converts an already square wave into the wibbly wobbly monstrosity at the top of this post.
I’ve found the problem, now how to I fix it??
I needed to work out how to turn a semi square wave into a sinusoidal wave with very little electronics experience, a knack for lucky guessing and a can do attidude. I put my dodgy soundcard scope on the output of the head and set to work.
I sang a childs rhyme (Ip Dip Dog Sh*t if you must know) and picked the first component I pointed at, a 4.7uF Ceramic cap. I bridged the wires on the head with it and hey presto!
Everything started working properly, and sounding great. As a bonus it cleared up the Harmonic distortion and as this means that a lower volume is required.
If you give it a try, let me know, I’d love to know how you get on.
I got impatient and killed the USB port traces of my Arduino Nano Clone whilst desoldering it. I should have used a heat gun but ran out of patience and thought I’d wing it.
I Googled it but there aren’t a lot of helpful docs for redirecting the USB port so documented it here in case anyone finds it to be useful.
I ran some tracing and checked the pinout for the CH340G and these are the alternate solder points.
I am extending the USB port for a project of mine and these points are way easier to solder to than the ones on the upper side of the PCB so it was a happy accident for me.
🙂
A TZXDuino smooshed into a Cassette Tape? Witchcraft!
I’ve built a TZXDuino device into a cassette tape, I didn’t think I could do it when I started but, as always, I’m glad to be wrong. 🙂
It’ll hold thousands of games and replace a cassette player. With this, you can load straight from the tape into a ZX Spectrum. As it seems that I need to prove that I’m not a witch (and I’m still pretty smug about that, thanks Twitter! ) and there are a few poeople that want to build their own I’ve documented the process here: https://github.com/jamhamster/TZX-Cassette-Mod/
I also made an overview on YouTube:
Give it a go, it’s a challenge but it’s worth it! 🙂
As the +2 gets no love, I thought I’d tinker with it and see if I could adapt the fix for the Toastrack Jailbars issue. I got very lucky and managed to exceeded the results they were getting on the toastrack.
I started with a Standard 128K +2 Issue 3 and the jailbars were very visible, especially over RGB. This has happened on every Grey +2 I have seen and is a ‘feature’.
I took a punt and added 1UF (B105) capacitors to the existing capacitors on the RAM bank to see if it helped and it did! I also swapped C52 from a 22uf capacitor to a 100uf capacitor. I tried different values but the 100uf capacitor worked best.
To sum up, swap C52 from a 22uf capacitor to a 100uf capacitor. Add 1uf capacitors to augment the existing capacitors in positions C72-C79. I am sure there is a more efficient way of fixing this but I am yet to see any published fixes for these machines. I ran the machine on soak for a few days and it passed all of the diagnostic tests so in its current state, the fix definitely helps more than it harms and you can’t argue with the results.
I also uploaded a video documenting the process. 🙂
I managed to get hold of a SCPH-3000 Playstation with what seems to be an older type PU-7 PCB and I couldn't find any diagrams for the Stealth 2.8a. I got it working and thought I'd snap a picture in case anyone else will find it useful, It's the same as the other diagrams but pin 6 is in a different place. Enjoy! :-)
Just getting this up and running for now, I’ll be back with something, I promise!! 🙂
JamBlog! 