Hi all - several people have pointed out (quite correctly) that the composite mod board should be grounded to the chassis. To be honest, I thought so too but it worked really well when I tested it that I didn't give it another thought! I'll solder it up and make sure to mention it in the next video! Good job you lot are on the ball! :) :)
I used to live next to the Timex factory that made the ZX Spectrum and when I was a wee laddie we’d sneak into the factory grounds and go dumpster diving. There must have been an extraordinary failure rate as there would be skips full of competed Spectrums that must have failed some kind of QC test. We’d occasionally (well someone’s big brother) manage to get them working.
Was that in Dundee? Do you mind if I ask the name of the road? I live in Aberdeen and regularly drive through Dundee and it would be nice to go and take a look one day!
I made a lucky discovery a few months ago, another benefit of replacing the 7805 with a modern switching dc converter is that it provides polarity protection! If you now use a supply with incorrect polarity all that happens is the Speccy won't power up!
Capacitor testers typically work by measuring the time it takes for the voltage across the component to rise to a particular level. The most likely reason those caps were reading larger than their rating is that they are leaking DC, basically they've developed a parallel resistance. This causes them to charge at a slower rate which fools the tester into thinking they have a bigger capacity than they actually do.
As a hardcore Spectrum fan and an electronic engineer I loved this, thank you! One comment about the units you used for that capacitor at 3:24. Am I the only one who calls μF "mikes" not "YouEf"? Once again a fantastic video, absolutely loved it!
Was promising myself I'd do this to my Spectrum over Christmas and still haven't plucked up the courage. Thanks for pushing me ever so slightly closer to damaging 38 year old electronics :D
Really enjoyed the video, I was going to add a comment about grounding the video mod but then saw your comment. Loved the power supply mod, I would not have thought of using a modem equivalent, that was a really great idea. Ironically I just finished a project using a buck converter so I should have thought of it. Thank you.
One thing I did with my ZX Spectrums is fit a heatsink to the ULA chip, just to be safe. I use ZX-HD - HDMI from byte delight. I use it on all of my ZX Spectrums and clones. The big problem now is finding a Raspberry Pi Zero for any of the addons. I need one for my Amiga upgrade. I might find one in 2023 at a very good price when my ZX Spectrum Next arrives. I have changed the Voltage regulators on mine.
A real keyboard sounds fun, I’ve got my Next in a 48k case and use a ps/2 keyboard to avoid using the dead flesh buttons. Having real keys would be cool. Also, doesn’t the composite board need a ground connection too, through the rf box casing?
It was a good thing you replaced those caps. I don't usually replace any caps just for the fun of it. I can live with old caps depending on the application. However in my experience, an unexpectedly (too) high capacity value in old equipment that wasn't powered on for a long time indicates some more uncommon type of capacitor degradation. I've had extreme cases where the capacity was doubled or even tripled while the ESR measured excellent, but these caps did not stand their rated voltage anymore and blew immediately on that voltage. Maybe your caps would have recovered over time when being powered. Maybe not. Thats not a gamble I would take.
I've never seen bad caps in spectrums. Even that primitive switching power supply for RAM chips is not demanding low ESR caps. The only cap replacement are needed if 7805 is replaced with that module. It may require LOW ESR caps near it.
Looking good! Was the interference in the picture resolved after the changes? If not what PSU are you using? It looks a lot like interference I saw before when using a cheap, switching power supply. If it's a known good one then forgive me!
Good shout - I’ll check a few different ones and see if the few remaining artefacts go away- I’ll also be soldering in that ground connection today too!
Yes, I thought so too but it seemed to be working just fine - I'll solder the ground in and see if it looks even better :). I'll make a note to mention this in the next video too :)
@@TheRetroShack Ground pads are on the edge of the PCB, so they probably have a decent contact with the chassis, at least until its surface will not oxidize.
@@pe1dnn I’ll be soldering it in tomorrow and will update on progress. I can only assume it’s accidentally grounding out at the corners because it’s a very tight fit. Maybe this is what’s missing to remove those final artefacts :) :)
I know it's an age-old argument, but rather than putting a Pi inside your Spectrum and replacing the keyboard, why don't you just run an emulator on the Pi and find a nice case for it? That way you'll have two Spectrums for the same price and effort. There's going to be very little of the Speccy left once you go down your current route. I'm not especially attached to Spectrums, but I have to wonder what the point is?
Just to clarify - there won’t be a raspberry pi inside the spectrum. The TK Pie is a cartridge that plugs into the rear of the Speccy :) Everything I’m doing is entirely reversible and no Spectrum’s will be harmed in the making of these videos :) :) :)
That looks to be the simplest RF mod I've seen done on a speccy, pretty sure even I could do that! So where can I get one of those boards from? And does come with the components to build it?
You can get these boards on Tindie and eBay (and probably loads of other places too) but if you search for 'spectrum composite mod' then you're looking for the PCB marked projectavr.com.
simplest way is just remove inside pcb and connect wire (el cap) from Video out to RF connector. 99% of TV are ok with it. If you have such crappy monitor, maybe monitor is the problem.
Unfortunately, it's a matter of trial and error as some TV's react differently to each option. The option that's most likely to work is option 1 - it's the option that actually you don't need this board for as you can simply put the capacitor in line in the video circuit but this makes it a little neater :) These kits are only a few pounds each so it's really only the time to build and test each option that needs to be considered.
This may be a bit excessively paranoid, but I worry that one day, hopefully in the distant future, this will be owned by someone else and they'll see the brown RCA jack and assume "RF", and then possibly think the Spectrum is dead when it doesn't give an RF output. If it were me I would have wanted to replace the jack with a yellow one to give future owners a clue that it's a composite output.
This is very bad, good work but you totally forgot to mention the jiggery pokery on your voice over commentary! This is a crucial part of the work you failed to mention! How is anyone going to be able to follow your work and re-do it themselves without you covering the jiggery pokery in detail on your voice over explaining? This is very very bad! You may make someone release the magic blue some in some poor speccy! Please update with jiggery pokery references and explanations!
@@TheRetroShack Horses for courses. Whatever floats your boat. One man's meat is another man's poison et al.,... I struggle to understand what is essentially a bog standard decades old MPU with barely enough memory to store a handful of instructions, let alone also a half baked set of input keys can created interest when a current MPU, designed today, with power, flexibility and integration potential can have so many noses thumbed at it. I've sat and watched many presentations this weekend adulating antiquated technology which even in its day, my day, was borderline obsolete even then. The biggest shock for me was seeing people carrying out first line repairs on VCR & CRT TV equipment and then playing back an image of barely around 400 to 625 lines of resolution and somehow marvelling at it. It goes beyond sentimentality. Even in my day, working in the largest CE service dept in the UK 20 to 30 years ago, much of what is being restored today on YT was considered absolute **it all those years ago. I carried out my microprocessor training in 1984 on large breakout boards using a Motorola MPU to study the ALU, stack pointing, instruction sets, shift registers memory allocation and addressing etc etc so I suppose the only purpose a Z80x serves today is to offer a atudent the chance to appreciate what is still applicable theory of operations in today's MPU at the most fundamental level. Else,.I struggle to understand why someone, anyone, would want to live in a cave in the 21st Century.
@@MarkHopewell Thanks for replying Mark and whilst I get your point I suppose the point is that feelings of nostalgia are deeply personal and rooted in your own memories. For me, like many others I suspect, it’s less about the adulation of the technology, it’s about what that period of time meant for me and the changing state of the world. As a kid, technically obsolete or not, going from a household with *no* computer to one with *any* computer opened up a whole new world of exciting possibilities. But ultimately, if it’s not for you, it’s not for you :) Thanks for taking the time to watch in any case.
@@TheRetroShack I understand. It's just that I formally trained on this stuff and went on the work with it for a living for 20 odd years or so. so I guess that's where my errr um 'reticence' comes from, comparing that level of technology to what the lucky students of today have access to. Having said that, I'm typing this from a current Nokia mobile phone with a touch screen. What I would give for a Spectrum ZX81, even with ust the silicon rubber keys to be able to type properly right now!!! All the best.
@@MarkHopewell I can only speak for myself, but my entry point into vintage computing is a desire to learn at a level when electronics where still of a complexity that you could understand them without an education within electronics. When it comes to making things for them, programming and HW extensions I think a lot of the attraction is a level playing field - making the most impressive thing within that limited capacity.
![เจ็บที่ยังฮัก - ม่อน วรวิทย์ [ Official Mv ] จอนนี่มิวสิค](http://i.ytimg.com/vi/KALIGSRSjFs/mqdefault.jpg)
Hi all - several people have pointed out (quite correctly) that the composite mod board should be grounded to the chassis. To be honest, I thought so too but it worked really well when I tested it that I didn't give it another thought! I'll solder it up and make sure to mention it in the next video! Good job you lot are on the ball! :) :)
I used to live next to the Timex factory that made the ZX Spectrum and when I was a wee laddie we’d sneak into the factory grounds and go dumpster diving. There must have been an extraordinary failure rate as there would be skips full of competed Spectrums that must have failed some kind of QC test. We’d occasionally (well someone’s big brother) manage to get them working.
How awesome is that (for you) and how damning is that (for Sinclair) :) :)
Was that in Dundee? Do you mind if I ask the name of the road? I live in Aberdeen and regularly drive through Dundee and it would be nice to go and take a look one day!
@@NotMarkKnopfler yes. We always called the road the “Timex Brae” but technically it’s Harrison Rd.
@@Bergkatse2 Was it the building beside JTC furniture - demolished back in 1988?
@@Fifury161 It was the building that became JTC Furniture. 27 Harrison Road.
I made a lucky discovery a few months ago, another benefit of replacing the 7805 with a modern switching dc converter is that it provides polarity protection! If you now use a supply with incorrect polarity all that happens is the Speccy won't power up!
What was the rf output like after you did that? I tried it on a QL, rf went crazy. I swapped it back.
Capacitor testers typically work by measuring the time it takes for the voltage across the component to rise to a particular level. The most likely reason those caps were reading larger than their rating is that they are leaking DC, basically they've developed a parallel resistance. This causes them to charge at a slower rate which fools the tester into thinking they have a bigger capacity than they actually do.
its a mod of famous Transitester. Just read how this thing work ;)
@@VShuricK I just did, and it works EXACTLY like I just said.
As a hardcore Spectrum fan and an electronic engineer I loved this, thank you! One comment about the units you used for that capacitor at 3:24. Am I the only one who calls μF "mikes" not "YouEf"? Once again a fantastic video, absolutely loved it!
Well, that Speccy is getting plenty of care and attention. I enjoyed the super slow-mo falling modulator moment.
It’s the little things isn’t it :) :)
Was promising myself I'd do this to my Spectrum over Christmas and still haven't plucked up the courage. Thanks for pushing me ever so slightly closer to damaging 38 year old electronics :D
Love how the spectrum + basically just had a plastic keyboard with the same circuit board as the 48k underneath! :)
Really enjoyed the video, I was going to add a comment about grounding the video mod but then saw your comment. Loved the power supply mod, I would not have thought of using a modem equivalent, that was a really great idea. Ironically I just finished a project using a buck converter so I should have thought of it. Thank you.
Glad you enjoyed it!
2:06 Robust Speccy FLASH command still going strong, even during test. Takes no prisoners.
One thing I did with my ZX Spectrums is fit a heatsink to the ULA chip, just to be safe. I use ZX-HD - HDMI from byte delight. I use it on all of my ZX Spectrums and clones.
The big problem now is finding a Raspberry Pi Zero for any of the addons. I need one for my Amiga upgrade. I might find one in 2023 at a very good price when my ZX Spectrum Next arrives. I have changed the Voltage regulators on mine.
This was my first spectrum.
A real keyboard sounds fun, I’ve got my Next in a 48k case and use a ps/2 keyboard to avoid using the dead flesh buttons. Having real keys would be cool. Also, doesn’t the composite board need a ground connection too, through the rf box casing?
I thought so too with the composite board but it’s working perfectly well without one, so go figure :) :) :)
Well I for one enjoyed that video 👍 40 years old and still going. 😜
Glad you enjoyed it :)
The intermittent fault, check the ula. Can be damaged by removing a peripheral while powered on, and mostly work afterwards
Thanks - I'll give that a go!
Another enjoyable video. Looking forward to the keyboard mod.
It was a good thing you replaced those caps. I don't usually replace any caps just for the fun of it. I can live with old caps depending on the application. However in my experience, an unexpectedly (too) high capacity value in old equipment that wasn't powered on for a long time indicates some more uncommon type of capacitor degradation. I've had extreme cases where the capacity was doubled or even tripled while the ESR measured excellent, but these caps did not stand their rated voltage anymore and blew immediately on that voltage. Maybe your caps would have recovered over time when being powered. Maybe not. Thats not a gamble I would take.
I've never seen bad caps in spectrums. Even that primitive switching power supply for RAM chips is not demanding low ESR caps. The only cap replacement are needed if 7805 is replaced with that module. It may require LOW ESR caps near it.
Looking forward to seeing the keyboard mid/upgrade.
Me too :)
12:22 Id leave the heatsink on so the unit feels the same weight. But thats just me. Thanks for the video.
Looking good! Was the interference in the picture resolved after the changes? If not what PSU are you using? It looks a lot like interference I saw before when using a cheap, switching power supply. If it's a known good one then forgive me!
Good shout - I’ll check a few different ones and see if the few remaining artefacts go away- I’ll also be soldering in that ground connection today too!
If you have composite video output, why not route the audio out through an RCA jack as well?
Thinking… :) :)
Nice video, thanks for sharing :)
Thanks for watching!
A good vid which I will use to upgrade my Spectrum :)
Composite mod board, should be grounded/soldered to the RF modlator chassis.
Yes, I thought so too but it seemed to be working just fine - I'll solder the ground in and see if it looks even better :). I'll make a note to mention this in the next video too :)
@@TheRetroShack Without ground it is just a capacitor, the transistor will do nothing....
@@TheRetroShack Ground pads are on the edge of the PCB, so they probably have a decent contact with the chassis, at least until its surface will not oxidize.
@@pe1dnn I’ll be soldering it in tomorrow and will update on progress. I can only assume it’s accidentally grounding out at the corners because it’s a very tight fit. Maybe this is what’s missing to remove those final artefacts :) :)
I know it's an age-old argument, but rather than putting a Pi inside your Spectrum and replacing the keyboard, why don't you just run an emulator on the Pi and find a nice case for it? That way you'll have two Spectrums for the same price and effort. There's going to be very little of the Speccy left once you go down your current route. I'm not especially attached to Spectrums, but I have to wonder what the point is?
Just to clarify - there won’t be a raspberry pi inside the spectrum. The TK Pie is a cartridge that plugs into the rear of the Speccy :) Everything I’m doing is entirely reversible and no Spectrum’s will be harmed in the making of these videos :) :) :)
My guess, let see ... POSTERITY! No, wait. SOLDERING IRON! Wait, I don't know. May I phone a friend?
Lol - that's why I asked the community to decide! I couldn't :) :)
5:30 so, you need no ground connection for the video adapter to work properly?
Check my pinned comment :) :)
@@TheRetroShack Sorry, I didn't read the comments. :)
That looks to be the simplest RF mod I've seen done on a speccy, pretty sure even I could do that!
So where can I get one of those boards from? And does come with the components to build it?
You can get these boards on Tindie and eBay (and probably loads of other places too) but if you search for 'spectrum composite mod' then you're looking for the PCB marked projectavr.com.
@The Retro Shack thank you very much for that, my Spectrum + will be living again soon 👍
simplest way is just remove inside pcb and connect wire (el cap) from Video out to RF connector. 99% of TV are ok with it. If you have such crappy monitor, maybe monitor is the problem.
This model is the only Sinclair Spectrum model I didn't have back in the day (The QL doesn't count!)
How do you select between the 3 options on the composite mod? -edit- as in how do you decide which is the best option?
Unfortunately, it's a matter of trial and error as some TV's react differently to each option. The option that's most likely to work is option 1 - it's the option that actually you don't need this board for as you can simply put the capacitor in line in the video circuit but this makes it a little neater :) These kits are only a few pounds each so it's really only the time to build and test each option that needs to be considered.
Nice!
This may be a bit excessively paranoid, but I worry that one day, hopefully in the distant future, this will be owned by someone else and they'll see the brown RCA jack and assume "RF", and then possibly think the Spectrum is dead when it doesn't give an RF output. If it were me I would have wanted to replace the jack with a yellow one to give future owners a clue that it's a composite output.
That’s an excellent point!
Or just put a sticker that says "composite" :-)
@@SimonQuigley That works too :) :)
See, the intermittent fail is not sorted yet! This is all because you forgot the jiggery pokery!
I think at least AY/YM addon a must. Not many games uses that in 48k mode, but hey no? :)
Please! It is micro farads!
Sorry - I'll try to use the correct terminology in future! I've been saying uf and nf since I was a kid - hard habit to kick! :)
👍👌
for caps measure esr
Many of the old axial electrolytic capacitors had a whopping 50% tolerance so we’re actually probably still ok. Even modern capacitors are 20%.
Good to know! I'm still glad I did the change though as it's not a lot of money or time and it's good for another forty years now :)
Upgrade my video cards for predictive modeling lol
This is very bad, good work but you totally forgot to mention the jiggery pokery on your voice over commentary! This is a crucial part of the work you failed to mention! How is anyone going to be able to follow your work and re-do it themselves without you covering the jiggery pokery in detail on your voice over explaining? This is very very bad! You may make someone release the magic blue some in some poor speccy! Please update with jiggery pokery references and explanations!
Christ.
?? What’s up Mark?
@@TheRetroShack Horses for courses. Whatever floats your boat. One man's meat is another man's poison et al.,...
I struggle to understand what is essentially a bog standard decades old MPU with barely enough memory to store a handful of instructions, let alone also a half baked set of input keys can created interest when a current MPU, designed today, with power, flexibility and integration potential can have so many noses thumbed at it.
I've sat and watched many presentations this weekend adulating antiquated technology which even in its day, my day, was borderline obsolete even then.
The biggest shock for me was seeing people carrying out first line repairs on VCR & CRT TV equipment and then playing back an image of barely around 400 to 625 lines of resolution and somehow marvelling at it.
It goes beyond sentimentality. Even in my day, working in the largest CE service dept in the UK 20 to 30 years ago, much of what is being restored today on YT was considered absolute **it all those years ago.
I carried out my microprocessor training in 1984 on large breakout boards using a Motorola MPU to study the ALU, stack pointing, instruction sets, shift registers memory allocation and addressing etc etc so I suppose the only purpose a Z80x serves today is to offer a atudent the chance to appreciate what is still applicable theory of operations in today's MPU at the most fundamental level.
Else,.I struggle to understand why someone, anyone, would want to live in a cave in the 21st Century.
@@MarkHopewell Thanks for replying Mark and whilst I get your point I suppose the point is that feelings of nostalgia are deeply personal and rooted in your own memories. For me, like many others I suspect, it’s less about the adulation of the technology, it’s about what that period of time meant for me and the changing state of the world. As a kid, technically obsolete or not, going from a household with *no* computer to one with *any* computer opened up a whole new world of exciting possibilities. But ultimately, if it’s not for you, it’s not for you :) Thanks for taking the time to watch in any case.
@@TheRetroShack I understand. It's just that I formally trained on this stuff and went on the work with it for a living for 20 odd years or so. so I guess that's where my errr um 'reticence' comes from, comparing that level of technology to what the lucky students of today have access to.
Having said that, I'm typing this from a current Nokia mobile phone with a touch screen. What I would give for a Spectrum ZX81, even with ust the silicon rubber keys to be able to type properly right now!!!
All the best.
@@MarkHopewell I can only speak for myself, but my entry point into vintage computing is a desire to learn at a level when electronics where still of a complexity that you could understand them without an education within electronics. When it comes to making things for them, programming and HW extensions I think a lot of the attraction is a level playing field - making the most impressive thing within that limited capacity.