Some info about the internals of the Inves Spectrum: Investronica had kind of agreement with Texas Instruments. You can see that almost every IC in the Inves is from TI. In fact, and due to one of the bugs the GA has, when replacing memory, it HAS to be a TI memory chip (more on this later). The PCB was manufactured and assembled by Sagitron S.A. in Spain. The Investronica technical person who passed away was Pedro Muñoz. He was in contact with Martin Brennan, from Flare Technologies. THAT was the company that designed and manufactured the GA. OTOH, Investronica, at the time, was about to import the C-5 into Spain, and for that reason, they sent a C-5 unit to Valencia to ask for homologation, but they got a "no no".
@zxprojects
4 жыл бұрын
About the reason why you need to use TI memory chips: the GA has one (well, several) bug that is triggered when you want to write a value to a I/O port managed by t he GA (that is, port $FE, write). To put it in a few words: when you write a value to port $FE, the GA also thinks you want to read from memory from the same address it has been used as I/O port address. The value that gets actually written to the GA is, then, the bitwise AND operation between the value coming from the Z80 and the value coming from memory. In the ROM, all accesses to port $FE use the OUT ($FE),A instruction, so the 16-bit address it is actually used is A*256+254. As bits 7 and 6 of port $FE are not used in a write operation, the ROM always set them to 0, so the 16-bit address is always in the range 0000-3FFF. Now that's the interesting part: there is 64KB of actual RAM in the Inves. the mechanism I've just described works the same no matter if it is RAM that can be addressed by the Z80, or RAM that lies behind the ROM (in fact, this is the only moment in which that RAM, and not ROM, is read). Such RAM is never written to by the ROM, even by the initialization routine, so this part of the memory keep its original content, the one it had when it was switched on. Due to how internals in a DRAM chip work, discharged cells in an even address are read as 1, while discharged cells in odd addresses are read as 0 (you can notice this if you press and hold reset while you switch on the machine and see which pattern is built on the screen). So, as long as all cells in RAM at addresses i*256+254 (where i ranges from 0 to 255) contains $FF, writes to port $FE will work as usual. Writes performed using OUT ($FE),A which A
@oldguy9051
4 жыл бұрын
Oh, Flare Technology (not Technologies) - figures as they were Ex-Sinclair people that were heavy in custom chip design (Flare One -> Flare II -> Atari Jaguar) en.wikipedia.org/wiki/Flare_Technology
@stevelupton2533
3 жыл бұрын
Hi Noel - as there's a 7812 voltage regulator on the board, the input voltage needs to be at least 14.5V.
@chainq68k
4 жыл бұрын
New Noel video? >clicks like< >proceeds to watch it< ... apart from this, free like just for presenting a machine I never even heard of before.
@zxprojects
4 жыл бұрын
Hi! Very good technical review of the Inves! Thanks for that. One thing I can tell to you is that the gate array is not a reverse engineered version of the ULA. It was a complete differente development from the scratch, and comissioned to a british company I cannot remember the name now. It has some resemblances to the 128K ULA, such as the absence of two crystals, using only one which generates both the dot clock and the colour clock. That alone should be enough for less noise composite video output. Using one crystal leads to the same amount of T-states per scanline (228) as the 128K, and the same scans per frame (311). Another original development inside the GA comes from the fact that the Inves has one memory bank, not two separated banks. This has an anormous implication: either all the memory is contended, or there is no contention at all: the GA exploited DRAM timings to the extent that all memory could be accessed by the Z80 with no delay, while at the same time, it was possible for the GA to read video memory in order to build the picture.
@NoelsRetroLab
4 жыл бұрын
Right. I figured that afterwards when I realized some of the functionality of the original ULA was implemented externally (interfacing with EAR/MIC and the joystick port). Very interesting. I wonder how much access to the original ULA (if any) they had.
@zxprojects
4 жыл бұрын
@@NoelsRetroLab Well, AFAIK, Investronica wroked side by side with Sinclair in the 128K design, so I guess they had plenty of access. Unfortunately, the Investronica person involved in all the technical stuff passed away some time ago. I will try to find out which british company was involved in the design of the GA circuit.
@pantaleonacci8087
4 жыл бұрын
Well, since nobody answered your question yet, I'll do it: yesterday I fired up my Inves Spectrum+ (which was indeed sold on eBay as a Spanish ZX Spectrum+) and thankfully no greenish tinge! Looking forward to part 2.
@NoelsRetroLab
4 жыл бұрын
Thanks! I was told the same thing in some other forums so... I guess I'm going back and researching what's going on! :-) Stay tuned.
@markevans2294
4 жыл бұрын
The earliest ZX spectrums had 16k as eight 1 bit chips and 32k as eight 1 bit chips. With the, uncommon, 16k models lacking the 32k bank (along with some address decoding logic). The 32k chips were actually faulty 64k chips. Some of the last ones produced using issue 3 boards allegedly have fully functional 64k chips fitted. On later board designs Sinclair went with eight 64k chips, with the lower 16k unusable. This clone takes a similar approach looking to use chips which are four bits wide.
@KolliRail
4 жыл бұрын
Wow, that was interesting! Never heard of that machine before. Looking forward to further compatibility testing.
@gertsy2000
4 жыл бұрын
Great video. Interested to see part 2. The mystery of the green tinge.
@NoelsRetroLab
4 жыл бұрын
Thanks! Hopefully part 2 will be the resolution :-)
@federicoachaerandio2698
4 жыл бұрын
Another great video from Noel. Thank you so much!!!
@gonzalo1972
4 жыл бұрын
Nice Sabre Wulf Tshirt 👍👍
@NoelsRetroLab
4 жыл бұрын
The goal was to play Sabre Wulf on that machine (since joystick is all but mandatory) but didn't get as far. Next time!
@CitroenGS
2 жыл бұрын
I have an Inves in my collection, and never noticed that greenish tint...
@jonyballistic
3 жыл бұрын
Excellent video, did not know about spectrum clone...⚡💯
@NoelsRetroLab
3 жыл бұрын
Glad you liked it!
@AnotherUser1000
4 жыл бұрын
You can put an electrolytic capacitor inside the modulator and disconnect the 5V power supply and modulated video output altogether, in order to have a better image quality. You just solder the one lead of the capacitor to the RCA jack and you drive the other one thru the whole of the shield, down to the PCB. This is what I did with my ZX Spectrum + and it works like a charm. It also makes it easier to reverse the changes, unlike with some other solutions that I have seen. If I wasn' t so bored right now, I would also upload the photos which I took. So, the only thing that it needs now, is to give it to a more skilled technician, ion order to correct the problems I created, when I started short circuiting the ICs with a screwdriver, when I was at high school... Greetings from Greece!
@frankowalker4662
4 жыл бұрын
All I can think of is check the resistors, ceramic caps and the traces around the video chip. (all of which is unlikely) Nice looking Speccy board. I like the layout.
@danweecc
Жыл бұрын
I would check the resistors used in the voltage dividers as well. They may be passive but the values may have changed over time.
@charlesdorval394
4 жыл бұрын
Quite interesting! Looking forward to part 2 :)
@mariobrito427
4 жыл бұрын
Oh wow that brings back memories. I'm from Portugal, so I owned a Timex 2048 clone back in the day, but i remember seeing the Inves during one of our trips to Spain. The 80s were interesting :) Thanks for the trip down memory lane! Great content, you got a new subscriber here for sure! (edit: double wow, it's great seeing a few Portuguese-made chips in there :D )
@NoelsRetroLab
4 жыл бұрын
Thanks! Glad you enjoyed it. Maybe one day I'll get my hands on a Timex and I'll make a video about it.
@JorgeCarvalho_web_dev
4 жыл бұрын
Hello Sir, found your channel due to YT suggestions, I love the content! You gain another subscriber. I am watching all the videos, please dont forget the SVI 328 :) Thanks for your detailed explanations showing part of the schematic that you are testing (SVI 328 and others). Really good content!!! Thank you a lot Sir. Best regards from Portugal
@NoelsRetroLab
4 жыл бұрын
Thank you! Glad you're enjoying it. And no, don't worry, I'm not forgetting about the SVI 328! As a matter of fact, here's a minor spoiler: I started shooting part 3, put in the new VDP, saw the clock signal working again, but the video was all colorless and weird... It turns out I had bought an NSTC VDP!! :-( So waiting for the PAL one to arrive to wrap up that series.
@WillBloodfarm
3 жыл бұрын
I had a QL! Thanks for the fond memories.
@NoelsRetroLab
3 жыл бұрын
Glad you enjoyed it! Did you see the series I did on the QL specifically?
@douro20
3 жыл бұрын
A textile machinery company- later to be acquired by Lectra- gets into the computer market.
@andresdominguez9333
3 жыл бұрын
Hi Noel, this is a great video! I don't know of anyone from Spain that had the Inves Spectrum (lots of friends with Spectrums from Issue 1 to Issue 4B, 128k, +2 and +3), in fact it's the first time I have heard of it. I read in a Spanish magazine about a late Spectrum with 64k chips instead of 16k + 32k chips, but I thought that it wasn't true. I was living in Tres Cantos where it is supposed to have been manufactured and I had no idea.
@NoelsRetroLab
3 жыл бұрын
Yes, it wasn't very popular. I'm guessing it was sold mostly to new users, so if your friends started with the original Spectrum, they weren't the target audience.
@CarlesOriol
3 жыл бұрын
There was created a law in spain that computers were required to have ñ key and imported ones with 64k were extremely over taxed. This computer was a way to sell spetrums it had more than 64k (16+64, look also for amstrad cpc472 that had 8kb that wasn't connected), and also the new symbol
@NoelsRetroLab
3 жыл бұрын
This particular computer only had 64KB (only 48KB usable) so it wasn't trying to do the same thing as the Amstrad CPC 472.
@CarlesOriol
3 жыл бұрын
@@NoelsRetroLab It's the same just to avoid taxes. cpc 472 never had usable more than 64 (they were disconnected!!)
@erikpiehl1764
4 жыл бұрын
Nice video, thanks for making these. As a Spectrum fan really enjoyed it. I realize the video is a few months old, and don’t know if this has been suggested already, but you could feed the video encoder with a clean power signal from the bench supply. For instance bend out the power input to the 1377, and feed directly from a clean source.
@NoelsRetroLab
4 жыл бұрын
You need to make sure they all have the same reference ground, but yeah you could. Are you suggesting that to avoid noise artifacts in the image? To be honest, the bench power supply is somewhat noisy as well the times I've looked at it with the oscilloscope.
@Xoferif
4 жыл бұрын
"McLeod" is a Scottish name, pronounced "mer-cloud". Check out excellent 80s film "Highlander", where the main character is from Clan McLeod. =) (But possibly avoid the sequels...)
@SoylentBlack1
4 жыл бұрын
pronounced "mah cloud". dont know where you got the "mer" from. Im Scottish BTW, and had a MacCleod great-grandparent
@pqrstzxerty1296
4 жыл бұрын
I am amazed China has not yet made a copy clone of the ZxSpectrum which advertised as 19TB of Ram, but in reality it has 17kb, and sells at $1.99 but ebay listed will be within three years .
@NoelsRetroLab
4 жыл бұрын
🤣🤣
@AlejandroJCura
4 жыл бұрын
Your pronunciation of "Miguel Angel Rodriguez” is spot on! Hope my English pronunciation is as good when I grow up. 🤣
@NoelsRetroLab
4 жыл бұрын
It helps that I'm from Spain :-)
@AlejandroJCura
4 жыл бұрын
@@NoelsRetroLab LOL, that explains it! 🤣🤣🤣
@andresdominguez9333
3 жыл бұрын
@@NoelsRetroLab Except for "Miguel Ángel Rodríguez" you have a very good English pronunciation. :P
@luisantoniogaitediaz2268
4 жыл бұрын
Noel, once more, incredible job by your side!!!!
@TaberBucknell
4 жыл бұрын
From my days, many years ago, working in Community Cable TV production ... the green tint was white balance (lack thereof) or a lazy RGB component. Sorry, best I can help. Request: Would you please do a scope usage walk through episode for those of us who barely remember using one (for me that was when oscilloscopes weighed as much as the CRT TVs being diagnosed 😉).
@NoelsRetroLab
4 жыл бұрын
Good suggestion. I'll make a short video on the basics of scope usage soon.
@vragec111
4 жыл бұрын
Wow for your video! And then wow again for some of the alien language people use in the comments! I'm fascinated what people remember, the voltages and all by heart!
@baze3SC
4 жыл бұрын
There's another interesting clone called Delta A02. I believe at some point a Yugoslavian company acquired part of the remaining Sinclair stock and released their own model which was basically a rebranded 48K+ Issue 6A assembled from pretty much the same parts. Unlike many other eastern European clones, this one had an actual Ferranti ULA and the same build quality. The other Eastern Bloc clone that had a genuine ULA was Czechoslovakian Didaktik Gama but otherwise it was a different design. I once used a faulty Delta for spare parts because I didn't want to cannibalize one of the surviving Spectrums :)
@NoelsRetroLab
4 жыл бұрын
That's really cool. There are some very interesting clones in East Europe. How could they get actual Ferranti ULAs though? There has to be an interesting story there.
@baze3SC
4 жыл бұрын
@@NoelsRetroLab I think Ferranti was initially unable to keep up with demand from Sinclair. As a result, many chips were ordered and produced. But then, Sinclair's poor financial situation combined with the release of 128K meant that nobody wanted these chips. Yugoslavia was a bit of a gray market country and they somehow managed to acquire genuine Sinclair parts. How they did it is a mystery to me. Once behind the iron curtain, Czechoslovakia was able to buy a batch of ULAs from Yugoslavia. Deltas were not even officially classified as computers but rather as teaching aids. They were literally sold at stationery stores instead of consumer electronics stores so that high commie officials don't get the wrong idea. At one point, Slovakian Didaktik company even acted as a semi-official Sinclair "repair shop" which enabled them to order another batch of ULAs directly from Ferranti and to bypass import laws. Ferranti probably knew what's going on but it was all good on paper. Today these stories sound strange :)
@andrewdunbar828
Жыл бұрын
Would like you to show us a 128k version of these some time. Those had both hardware and software differences too.
@damianvila
4 жыл бұрын
Investrónica > INdustria, VEStido y elecTRÓNICA (Industry, garment and electronics). "Inves" still exists today, but it's just a consumer brand from El Corte Inglés, to put in cheap product imported from China.
@davidblackuk
4 жыл бұрын
great video as usual. Please cover the sinclair QL soon. i have one that I haven't turned on yet because i'm unsure how to troubleshoot issues and don't want to risk it
@chessoc7799
4 жыл бұрын
Never heard of these. At least it looked like a Sinclair machine :)
@NoelsRetroLab
4 жыл бұрын
Oh, they made sure that they looked a LOT like a Sinclair machine. I bet most kids getting one didn't realize it wasn't one.
@MMSZoli
4 жыл бұрын
Nice video! I wish you success with that green tint. It is interesting, that it QL video IC, as for me the two machines looked competely different from gfx poit of view. QL never had 16 colors, just 8 (similar to Spectrum's brighter 8 color) and 4 fixed in hires mode. It has 256x256 and 512x256 resolution with no attribute (VS Spectrum's 256x192 attribute gfx), so I am curious how all these will fit into the 48K, or how much of it's potentials will be used. Seems that QL IC has more possibilities than I thought... At QL's release, the QL's higher 512x256 resolution with 4 fixed colors (black, white, red, green) was more capable than IBM PC's CGA 640x200 with 2 colors and the 256x256 with 8 fix colors still looks better than 320x200 with 4 fixed colors. So it was not outstanding, but was not "bad, bad". ( I am mainly a Commodore16 / Plus/4 fan, released almost at the same time as QL, and also advertised as a home office PC as the QL. I really felt that QL deserved more success, but the maximum 8 colors for me is a too strong limitation (I can use 121 colors on C16 for gfx). Anyhow, it will be be interesting, if any unofficial new gfx ode will pop up, like the 512x192 in Timex machines (pretty good for text editors, and GUI)
@NoelsRetroLab
4 жыл бұрын
Oh I'm afraid it isn't anything that interesting. The IC just takes care of converting the RGB signal into a PAL composite video signal. That's the IC that the QL and the Inves have in common. The ULA, which controls the video modes, is completely different. So no hidden video modes in the Inves I'm afraid :-) (although we could do something to use the full 64K of RAM!).
@MMSZoli
4 жыл бұрын
@@NoelsRetroLab thanks for clarification. The Timex 512x192 pixel mode was a kind of surprise to me. I think we could kill for such a resolution on Commodores :-) Imagine GEOS with that on C64 (yeah, I know C128 had a version with 640x200).
@BertGrink
4 жыл бұрын
Is it possible that the previous owner has modified the ROM to give cyan paper and border? Try doing a PAPER 7: CLS : BORDER 7 and see if it turns white ;)
@NoelsRetroLab
4 жыл бұрын
Oh wow, I didn't even think of that! That would be devious! :-) But I don't think that's the case because the diagnostics ROM (which I didn't show here yet) shows a greenish screen as well. I'll try that just case.
@NoelsRetroLab
4 жыл бұрын
OK, it gets points for thinking outside of the box, but I just tried that and still the same :-)
@BertGrink
4 жыл бұрын
@@NoelsRetroLab Uff, that's a shame; it could have saved you a lot of troubleshooting if that had been the case.
@iloveu4evergirl
4 жыл бұрын
ese es para el mercado ingles, yo compre en japón en un mercadillo la version española (con la letra Ñ), cuando era niño tuve un plus en ingles !
@rushglider
4 жыл бұрын
Could you explain how to clean the noise image of the ZX Spectrum +2ab / +3 models
@NoelsRetroLab
4 жыл бұрын
It's on my list of things to do. First I need to do some testing. Don't worry, if I come up with anything, I'll make a video about it.
@abandonedmuse
Жыл бұрын
I am looking for one that my dad bought me in 1980 when I was five years old and it looks like the ZX spectrum but it is not because I do not remember the rainbow on the side. It came with a couple of word games a couple of math games, and what I believe to be the adventure game, the text dungeon crawler if you know what I’m talking about can you tell me the model number because I’ve looked for it everywhere and everybody says that he started in 1982 but I know for a fact that he gave it to me when I was five years old so it had to have been in 1981 or 1980 thank you
@captaincorleone7088
4 жыл бұрын
I knew of the Russian clones but not this one! What standard does the joystick port use? Is it Kempston?
@NoelsRetroLab
4 жыл бұрын
Yes, it's a Kempston standard, so that's perfect for that time period.
@sakisyoutuber
4 жыл бұрын
Weird ZX Spectrum+
@skonkfactory
4 жыл бұрын
It's possible that the chroma crystal has drifted in frequency or that one of its trim capacitors has drifted in value. Also possible that the resistors between the RGB inputs on the 1377 and the outputs on the ULA have drifted in value, though less likely.
@NoelsRetroLab
4 жыл бұрын
But there's no chroma crystal that I can see! Just a master clock that then gets divided (I'll get into it next video). Also no trim capacitors that I can see. The other weird part is that on screens with other colors, everything looks great. Maybe it's just a slight green tint and it's only noticeable on a gray background.
@oldguy9051
4 жыл бұрын
@@NoelsRetroLab I think with "trim capacitors" the capacitors with fixed but specific values are meant. I'd check the clock frequency next. Also: I suspect that the first part of the name "mcleod_ideafix" is possibly based on the Scottish name. See Wikipedia for correct pronounciation (or the Highlander movies ;-)).
@NoelsRetroLab
4 жыл бұрын
Ah, I thought he meant trim capacitors as in adjustable ones. I'm looking into the clock frequency right now. Unfortunately the division happens inside the ULA, so I suppose that could be bad (and no way that's easy to replace). I will look at the master clock and even try replacing the Xtal just in case. Oh and I'll check the pronounciation. It's been too long since I watched Highlander :-)
@zxprojects
4 жыл бұрын
@@oldguy9051 Indeed! I chose that nickname because of the Highlander movie. Ideafix is/was the name of a dev group I involved into during the 90's (much like a demoscene group, but with much less glamour)
@skonkfactory
4 жыл бұрын
@@NoelsRetroLab Is it like the 128k Spectrum where there's a 17.7345 MHz crystal that is driven by a 74S04?
@petergerkman244
4 жыл бұрын
Have legs 11 and 12, 100nF ceramic capacitors, try replacing them.
@NoelsRetroLab
4 жыл бұрын
That'd be on the MC1377P, right? So the color components? I can give it a try, but I've never had a ceramic capacitor go bad. I'll let you know.
@petergerkman244
4 жыл бұрын
@@NoelsRetroLab I have seen several times changed the ceramic capacitor internal resistance up to short-circuit.
@pantaleonacci8087
4 жыл бұрын
Ah, and the motherboard is the latest version, like yours.
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