Ben has modded many old computers into gaming portables and in this episode Ben returns to an old friend - the ZX Spectrum. In this episode he completes the project. bit.ly/1jh94OG Learn more about Analog Devices at bit.ly/1Oq2GQU
Watching this show again is relighting my motivation for creation, I've been DIYing cases for things for a while and jury rigging stuff (Xbox one most recently) But now I want to do an electrical engineering course or something so I can properly understand these old circuits and how they work.
Dear Ben & the Team, just an appreciation for that excellent & inspirational work there! This is rich & engaging in its imaginative & creative energy. Thank you for sharing the fun
Had you considered the possibility of putting the two main ICs on the back of the main board, in order to reduce the thickness of the screen area? Would that have caused problems in PCB layout, or maybe prevented you from mounting a heat sink? Had you considered milling fins on the heat sink to increase surface area and therefore heat dissipation, or was your existing design sufficient for the ULA's heat output?
Great job Ben. I can think of a bunch of things that could've been included here but of course as you have mentioned the schedule for these episodes is tight. But if time and board space allowed for it I would've probably added the following. 1. Composite video out port for connecting to a CRT or LCD tv. 2. integrated USB keyboard circuitry. Some modern expansion devices include this. 3. Integrated the DivIDE (or similar) circuitry for fast loading of games from CF/SD cards. 4. Bus expansion port for adding any of the modern expansion devices built these days. With the above added you could carry with you a device that can load thousands of games at lightning speed. It can also be used like the original unit by plugging in an external keyboard and TV and possibly a joystick of that expansion device is added.
Is there a way to emulate the behavior of a PCB on a computer before sending it to be manufactured? By that I mean something like being able to load a program onto the emulated computer (a "virtual ZX Spectrum" in this case), to test it and avoid having to mod it later. I understand the thing about time constraints, but y'know, Ben had to spend more time compensating for that. I loved these episodes, by the way. It's great seeing him build a whole retro computer almost completely from scratch. Hope there will be more like them in the (nearest) future! I wouldn't mind if it needed a third episode...as long as they were uploaded in sequence! (grumble-grumble -- **shakes fist**)
15:16 FYI, the extra space in the load command isn't required with the original ROM. 21:05 The ULA runs warm because the Speccy actually drives the Ferranti ULA above Ferranti's design specs for the chip, using more of the gates at once than Ferranti actually expected. But hey, if it's still working in 2015, I think we can probably call it a stable design.
You sure know your stuff Ben! It's good to see you make mistakes and just get stuck in.......I wish I could do what you could......to be able to build so many cool things......and put together a whole spectrum....wah!
This is fantastic, I am always in awe of your engineering knowledge and skills Ben. There are plenty of ZX Spectrums still in existence, you can pick one up for quite cheap, what I was wondering is can you make an MGT Sam Coupe, a ZX Spectrum compatible 8 bit computer with better graphics and sound. These are much rarer and much more expensive, so if you could engineer one for cheaper than you can buy a 2nd hand one, it would be most interesting.
That would be awesome! I've never seen a Sam Coupé in RL, Those were very very rare in Holland. A normal pcb that fits in a regular pc case would be fine :)
Hey that's a great episode. Thanks for spending some time showing off the finished product from different angles, as well. That was very nice. Cool project and great result. I think Ben is right when he says it's one of his better builds. Now, the only thing is the audio in most of the episode is a lot quieter than the intro and Tech Time Out. Maybe the mics' gain were down?
ZX81 had a simple modification used at the time. A switch called a video inverter. It just switch black with white and that is about as simple as you get.
Ben, it's good to see you using 123d more. I wish 123d could export sketches. Then you could laser cut from your 3d model rather than having to lay out all your parts twice. One trick I've found when printing enclosures with a curved face is to print them face up (i.e. opposite of the way you printed it), but to use support material underneath, which you then remove. For some reason, printing a curved shape works better this way. I think it's because the layers underneath tend to sag. In any case, the interior of the case will be a little rougher this way, but who cares? I'm experimenting with sanding PLA. I also found an epoxy sealer for smoothing 3d prints, but have yet to try it. It's called XTC-3D.
I think the device looks great and with the 80's theme maybe add a removable, flip, or slide cover over the keyboard for storing and decorate that as well.
Hi Ben, Very nicely done mate, almost perfect in fact. I think I would prefer yours over one of the re-designed and commercially available ones. If you could include a memory card to have games instantly available rather than have to load tapes, this would be more desirable. The finishing touch would be the spectrum colours in the corner...a perfect modern speccy. OH and maybe a USB for a joystick?? Yes Zed is better than zee and also we say soLder with the L and not sodder which doesnt have an l :) Just a UK-USA thing mate!(one of many) Finally, I have just watched all the videos you have on speccy reworks and have thoroughly enjoyed them, well done mate. I hope to see more on the speccy from you. I think your design would be a sell-out in the UK with all us 40ish guys.
You could have put 2 extra bit planes and 4 colour tables in the 16kB hidden, and some nibble pairs for multiplying the regular and extra screen bitmaps. Maybe the ULA in a CPLD, and given the speed of modern parts, it might have been possible to CPLD a RISCy set of micro-ops to make a simplified Z80 via little subroutines in the mem too, all in one CPLD :D
a more modern equivalent voltage regulator negates the need for a heatsink on the 48k speccy (and toastrack) which also reduces the ULA temperature too
Love how 80s this looks. So period specific. Also love that you use as a £650 phone, with oodles of power to load it. some type of irony in that I'm sure.
So here we have a complete working smaller ZX Spectrum, created by one person over a few months. And then elsewhere on the Internet we have the ZX Vega :-/
+10p6 Actually you might as well get a Raspberry Pi and run FUSE. Even allowing £20 for peripherials you're gonna need, you're still about £50 up over the VEGA and have a far more capable device. I'm hoping someone retools Ben's speccy board so that it can take original keyboards and be used in the original case. Also seems like there's some scope to emulate parts of the ULA using a cheap microcontroller. Imagine using something ike an Arduino to load ROM images from SD card, dump them into the memory, set the processor state and drive a clock signal to the z80, thus bypassing (and eliminating the need for) tape loading entirely? Also, this seems like it would dovetail nicely with Ben's Master System/Colecovision/CPM z80 project.
Was having a similar issue (RAM not being activated) in a Z180 project I'm working on, but thankfully it wasn't a hardware problem. It turns out that you have to use the Z180-specific I/O instructions to work with internal peripherals, like the MMU (doh!).
The design of this version is great. I love the gold and black colouring, it definitely looks like something out of the 80s. Could you do something with a C64 next? This was my first computer and I remember playing some great games on that like Dizzy. Also the music from the C64 is great.
15:08 Technically you were supposed to put the name of the programme to be loaded inside the quote marks. However leaving it blank would load the first program you throw at it.
you could have made the screen section a bit thinner if you had inverted the front am back of the main board underneath. have the z80 and ula on the back, and the multiplexers on the front. also the ula's multiplexers arranged inside the ula the way you did with the z80's
for some reason it reminds me a lot of the first game boy :-D . How about adding a power indicator using an RGB led so that you can also display battery level. You wouldn't want your space invaders game end just because you didn't know how much battery is left!
Would it be possible to smooth out the case a bit? I was thinking maybe fine grit sand paper on the outside of the case to smooth down the lines that formed from the 3D printing, and/or maybe use a bit of acetone to give it a smoother finish.
I would like to see if this could be done with more complex computers such as the Amiga 500 or Atari ST of the 16 bit era. These were the computers that most people switched to when the Speccy and C64 had become too outdated. They would also be better for a hand-held game system because of their better resolution options, colour pallet and hard drive support (SCSI) which can be converted to memory card for storage. The main problems would be the amount of custom chips (mainly on the Amiga) and squeezing in all the functionality while keeping the size down and providing adequate power.
Well designed, actually pretty attractive. My first compute was a zx81 I bought from a garage sale in 90 or so, came with the books and everything, taught myself how to program it. Now look at me, making dumb comments on youtube.
18:09 Spark! What shorted? The battery isn't even connected. Also funny about the PU resistors under the IC, I nearly had that bite me today, so easy to forget about component outlines.
One thing I did spot was that the spectrum seemed to initialise very quickly. This would imply it's only detected the bottom 16K of memory, and not the full 48K. I'm also not sure why Ben chose to use the original Z80 chip here... I probably wouldve used a modern PLCC packaged one which is CMOS and would consume much less power. edit: judging by the fact that the games all work, I'd say the GW ROM mustve sped up the initial RAM test!
11:00 or they called them bodge wires, or they were just part of the design because adding another layer was not feasible but running a couple of wires instead of these traces was.
I liked my keyboard....a lot ,and my microdrive.I did the interupt mod no internet in those days had to wait for weeks for answers in computer magazines....always trying new tapedecks and ajusting the azimuth for sweetest loading....can you print silicone?
5:14 -- Whoa, a "whoosh" sound there with no graphic going with it. Also, what happened to the video encoding? Ben's mouth glitches many times during the final "what have we learned" bit.
I always wanted a speccy laptop, with a decent sized screen, at least 14". A decent keyboard is a must, not the dead flesh feeling keyboard that was original. and to be able to switch from the original ROM to a "better" modded ROM on the fly is a must. I don't see why such a project couldnt have the circuits added for the joystick ports, since they are only a couple of A/D chips. If you really want to go all out, add a sound chip. I think that was an option back in the days when this was fairly new, a add on circuit that a person could purchase and connected to the rear bus. Maybe I am wrong?
I remember working with the Zilog ZEE/ZED? 80 in engineering class about 23 years ago and while the construction techniques are interesting and I enjoyed the series, I'm wondering why? I haven't used a tape/audio drive programming since my Commodore VIC-20 and it was all typing 1&0 machine language code (maddening). Pascal was sent from heaven and C- was oh wow!
+Stuart Wilson I was an electronics technician when affordable Personal computers were first introduced. I worked my way from the Vic-20 to the C64 to the Commodore Colt (XT clone) in the late 80s and after teaching myself basic and pascal. I graduated to C/C++ on the 486sx in college. I still have my Colt but its wrapped up in the attic now. Just couldn't part with Old Sparky.
I have 2 polycarbonate MacBook shells with failed logic boards but working screens - do you reckon a ZX Spectrum mainboard would fit in the shell keeping the MacBook battery and magsafe to make a SpecBook?
Ben, i would very much like to have seen the whoe 3d design because i would have like to learnt about the software and how to do things you did, like curved edges.
It resets too quickly. Unless part of the reset routine was edited out, it looks like the Speccy only sees 16K or RAM. (Manic Miner was written for the 16K Spectrum.)
