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Redesigning a ZX Spectrum 128k - my childhood dream
- Thread starter myPinballs
- Start date
Plenty come up for sale on eBay. Look for ones that are either untested or broken. As long as the keyboard membrane is ok (cheap to replace if not) it should be fine for Jim's Spectrum.
https://www.ebay.co.uk/itm/272415919102
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Exactly what i was going to say. The board is designed to fit original plus cases. So have a look on ebay for non working ones or empty cases. New keyboard membranes are only £10 or so and are definitely worth it to
Aaaah sod it. I've grabbed a tested and working, boxed ZX Spectrum+ off eBay. Got all cables included and about 30 games.
I'll look at slinging an order in for one of your boards Jim but it might be a few weeks now as i've got some expenses coming up as I start to rebuild Rocky & Bullwinkle. Any idea on when you'll be starting production on the pre-ordered boards?
I'll look at slinging an order in for one of your boards Jim but it might be a few weeks now as i've got some expenses coming up as I start to rebuild Rocky & Bullwinkle. Any idea on when you'll be starting production on the pre-ordered boards?
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Board blanks are due to be order shortly along with the second batch of my custom pinball controller boards. I am starting to gather the parts for assembly to. I think a month or so before i start putting them together.
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There will always be some modification to the lower half of the case as there are many new features and ports on my board such as scart and kemptson joystick port. Old cases are plenty full, so its no big deal really
It's not a problem Jim, but just something useful to know ahead of time.
There's no issue with me breaking out the drill if required and for larger access ports i've got a dremel that i'm sure could be used to do a nice tidy job.
There's no issue with me breaking out the drill if required and for larger access ports i've got a dremel that i'm sure could be used to do a nice tidy job.
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Yeah a dremel should do it quite nicely. I have an idea for maybe new 3d printed lower cases someday, but at the mo its just modify originals.
3D printed stuff tends to be expensive my millennium falcon upgrade bits are stupidly expensive for the size
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But cheaper than creating injection moulding plus your don't need to order min 5000
It's the tooling that's expensive hence the min order sadly. We have had to do it at work before
Make sure you download Speccytape to your smartphone or tablet !
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Well, things have been a little hectic here recently with pinball board assembly, but i managed to rejig my dev office in the last few days and finally get a place for my proto zx spectrum setup so I continue the final tweaks and adjustments before getting batch 1 of the board blanks made.
I like just turning it on and seeing the os screen whilst i'm up here doing boring things like creating bill of material files, entering electronics expenses and filing vat returns. It certainly makes me smile more
I like just turning it on and seeing the os screen whilst i'm up here doing boring things like creating bill of material files, entering electronics expenses and filing vat returns. It certainly makes me smile more
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Amazing how much fun this type of childish humour is! and how quickly you remember the old basic language!!
Now, don't forget i own the copyright to this software masterpiece and you all have to pay a licence fee to use it
Now, don't forget i own the copyright to this software masterpiece and you all have to pay a licence fee to use it
Still time for me to get an order in for one of these then Jim?
Does the SCART socket also output audio or do you have to use the seperate line out for that? Also, is there any onboard beeper or speaker for audio playback? One of the issues I immediately found with my new 48k Spectrum was that the audio was always played on the beeper which meant I couldn't play anything whilst the missus was watching TV. For now i've wired a switch in place so I can turn the onboard beeper on and off.
I've finally got my hands on an original ZX Spectrum 48+ and i've been messing around with it over the christmas period. It was great to replay some of the classics even if at first the crippling loading times of 4-5 minutes was a little painful.
Then after a bit of googling I strayed across this article. It talks about using a program called OTLA to modify the original loading data so that the baud rate is much higher. It turns out that the Spectrum used a lower baud rate because at the time the audio quality from a tape wasn't so great so a slower speed was chosen in order to make for more reliable loading. Of course nowadays with digital playback things are a tad different so we can try at a quicker speed.
Yup, I tested it out and Manic Miner went from taking 3m 10s to load, down to just 25 seconds. I'm quite staggered by that and also the fact that this tech has been around for ages yet it's the first time i've heard of it.
Does the SCART socket also output audio or do you have to use the seperate line out for that? Also, is there any onboard beeper or speaker for audio playback? One of the issues I immediately found with my new 48k Spectrum was that the audio was always played on the beeper which meant I couldn't play anything whilst the missus was watching TV. For now i've wired a switch in place so I can turn the onboard beeper on and off.
I've finally got my hands on an original ZX Spectrum 48+ and i've been messing around with it over the christmas period. It was great to replay some of the classics even if at first the crippling loading times of 4-5 minutes was a little painful.
Then after a bit of googling I strayed across this article. It talks about using a program called OTLA to modify the original loading data so that the baud rate is much higher. It turns out that the Spectrum used a lower baud rate because at the time the audio quality from a tape wasn't so great so a slower speed was chosen in order to make for more reliable loading. Of course nowadays with digital playback things are a tad different so we can try at a quicker speed.
Yup, I tested it out and Manic Miner went from taking 3m 10s to load, down to just 25 seconds. I'm quite staggered by that and also the fact that this tech has been around for ages yet it's the first time i've heard of it.
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Yes, you can still get in the pre-order queue for my boards. As with all my products its first come first served. I will be making these for as long as possible.
The SCART socket included on my design is official spec RGB SCART with full Left & Right Audio out to TV. The audio is outputted as single channel to both left and right at the moment, not stereo, though i am looking at possible updates to take further advantage of the sound chip. (the chip is actually 3 channel and much of the 128k music was in fact created as 3 channel, but then mixed to singe channel before being outputted on the original machines). Your TV will detect the signal correctly and announce the inbound signal as RGB SCART to unlike many cheap nasty convertor cables about.
Cheers Jim.
I picked up a tape player today to try out some of the old games that came with the Spectrum. Unfortunately none of them will load at all but I think that's because the tape player is outputting stereo and the input on the Spectrum is mono only. I'm presuming I just need a stereo to mono converter and that should solve the issue.
I picked up a tape player today to try out some of the old games that came with the Spectrum. Unfortunately none of them will load at all but I think that's because the tape player is outputting stereo and the input on the Spectrum is mono only. I'm presuming I just need a stereo to mono converter and that should solve the issue.
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Shouldn't matter. Stereo lead should still function as mono is normally outputted on both channels together. What type of tape player did you get? Is it a new one? This is why remakes are a good idea
Yeah, it's a new one. Actually it's one of those which is designed to rip tape to MP3 audio via a USB cable, but it also includes a headphone jack which is where i've hooked up my cable which runs to the EAR port.
Could well be the tape drive at fault. I've tried hooking up various sets of headphones too and it's been a bit hit and miss. Some headphones, such as those that came with my mobile, give no audio at all whilst the one that came with the device work fine.
Behaviour is as if the Spectrum just isn't hearing the audio. The load command creates the borders but it doesn't seem to register the signal when playing the tape back.
Edit: A cable with two connections on each end, one grey and one black was provided with the ZX Spectrum. From what I recall each 3.5mm plug is only wired up for a mono signal and that's what i'm using, but i've also tried using a stereo 3.5mm lead as well. Neither worked. Most odd.
Could well be the tape drive at fault. I've tried hooking up various sets of headphones too and it's been a bit hit and miss. Some headphones, such as those that came with my mobile, give no audio at all whilst the one that came with the device work fine.
Behaviour is as if the Spectrum just isn't hearing the audio. The load command creates the borders but it doesn't seem to register the signal when playing the tape back.
Edit: A cable with two connections on each end, one grey and one black was provided with the ZX Spectrum. From what I recall each 3.5mm plug is only wired up for a mono signal and that's what i'm using, but i've also tried using a stereo 3.5mm lead as well. Neither worked. Most odd.
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Ha, scratch that. It does work but it was me being an idiot that caused the problem.
Whilst testing i'd got confused about how far onto the loading process i'd progressed. Turns out it was trying to load the second block of data without the prior segment being loaded. This causes the weird issue that it displays the 'Bytes' message but it won't accept the remainder of the data.
Rewired it up using a standard stereo 3.5mm lead and tried from the start of the tape and it works just fine now.
Nice
Whilst testing i'd got confused about how far onto the loading process i'd progressed. Turns out it was trying to load the second block of data without the prior segment being loaded. This causes the weird issue that it displays the 'Bytes' message but it won't accept the remainder of the data.
Rewired it up using a standard stereo 3.5mm lead and tried from the start of the tape and it works just fine now.
Nice
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Well things have been super hectic with all the pinball stuff I'm making so not had a lot of time on this project recently, but i did work on some tweaks and checks for the board positioning and fit within the original zx spectrum plus case bottoms yesterday.
Also been working on some additions to add a VGA connector to the board from some feedback i got. SCART isn't used a great deal over in the USA apparently. The VGA connector should align with the case holes for the old audio outs which is handy.
Other mods needed to the case will be for the SCART out, Audio outs and Kempston joystick out, but have all been placed to make the changes as easy as possible. The kempston interface is at the front where the old heat vents are so this is extra easy to adapt. The edge connector expansion and power in line up with original holes so no mod needed there.
Also been working on some additions to add a VGA connector to the board from some feedback i got. SCART isn't used a great deal over in the USA apparently. The VGA connector should align with the case holes for the old audio outs which is handy.
Other mods needed to the case will be for the SCART out, Audio outs and Kempston joystick out, but have all been placed to make the changes as easy as possible. The kempston interface is at the front where the old heat vents are so this is extra easy to adapt. The edge connector expansion and power in line up with original holes so no mod needed there.
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version v0.5 blanks are now with the manufacturer. I made some updates to add stereo sound capability on aswell. If all goes well and all updates from the v0.2 proto boards are all good then i'll be in a position to make up some for people.
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version v0.5 board arrived today
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10 Print "I Love Pinball"
20 Goto 10
Ha. Those were the days
Those are still the days if you so wish
I've been slowly disassembling Manic Miner using an assembly dump that I generated a few months back.
Really gives you an idea as to just how hard it was to get the Spectrum to do even the most basic of things. Just displaying the opening screen and playing that tune was several hundred lines of assembler.
Fascinating to read the Z80 reference where it tells you how many cycles each command takes to execute, because back in those days it was all about doing things as efficiently as possible.
Really gives you an idea as to just how hard it was to get the Spectrum to do even the most basic of things. Just displaying the opening screen and playing that tune was several hundred lines of assembler.
Fascinating to read the Z80 reference where it tells you how many cycles each command takes to execute, because back in those days it was all about doing things as efficiently as possible.
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Latest board testing. Waiting for some newly sourced keyboard connectors to arrive then will be final testing the stereo sound and joysticks. Video tests complete.
Made the required mods to a standard plus case and mounted board inside. Love the easy position of the joystick port and sound connectors.
No mods needed for these.
Made the required mods to a standard plus case and mounted board inside. Love the easy position of the joystick port and sound connectors.
No mods needed for these.
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Some pics of the VGA optional extra connection. This output is similar to how i've created pinball 2000 lcd conversions. The output from a pinball 2000 (Stock) and the zx spectrum rgb scart are similar in design and frequency. Uses the readily available gonbes arcade vga convertor board with 2 vga cables. No custom cabling needed. Just 2 vga stock cables needed.
Correct aspect ratio to or screen fill as above.
Correct aspect ratio to or screen fill as above.