QL test points...

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Dave
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Re: QL test points...

Postby Dave » Sun Mar 03, 2019 6:53 pm

I had googled a couple of times and not found it. Maybe I was using the wrong search terms? I last looked about two years ago.

I just looked again and boom, it popped right up. It's on Dilwyn's site, because of course it is!

Sooo, anyone going to recommend any useful test points they'd like, or think might be useful to the community in general?


Nasta
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Re: QL test points...

Postby Nasta » Mon Mar 04, 2019 8:53 pm

Most signals can be observed on the pins of the DIP chips...
That being said:
1) Forget the exact position of the 68008 - nothing serious used that as the original socket was a POS and taller than all the others.
2) Duplicate pins (through-hole pads) for a vertical J1 right behind the original J1, with a bit of spacing from the original.
3) Duplicate pins (through-hole pads) for the ROM slot behind the original ROM slot.
4) LEDs to show the status of all power supplies (and maybe the RESET_IN line), perhaps small SMDs on the board.
5) I may think of some more :P


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Dave
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What the test points are going on...

Postby Dave » Sat Mar 09, 2019 2:02 am

I made some progress.

Here's some 3D renders:

The CPU, 8301 and revised DRAM layout. Note DRAM is socketed, and bank 1 can be removed if you're using a SGC. Also, note the extra header row inside the ROM port, which also has a few extra pins - enough for an internal fast SRAM expansion if you want one.
Screen Shot 2019-03-08 at 7.11.38 PM.png
The business end...


For the ROM slots, they have the exact position and spacing of the originals. Note the little jumper, so you can use QL JM/JS ROMs or an EPROM without using an adapter board. Also, the serial output has been switched from MC1488/1489 pair to ADM208EAR. The MC1488/9 required +/-12V, and it was easier to change the IC than incorporate those nasty power supply requirements. Also, note the serial and joystick ports are DB9 connectors... In black.
Screen Shot 2019-03-08 at 7.10.49 PM.png
The business middle...


RGB out is now fully buffered and protected. Power in is 9V from a standard 2.1mm power supply. If you have no expansions, a 500mA one will work. If you're going to plug a city of retro electronics into it, you might want a 2 or 2.5 amp 9v adapter. There is a power switch. And yes, those are QLNET ports.
Screen Shot 2019-03-08 at 7.31.44 PM.png


This is Issue 7.5, but I renamed it to Issue 8 because there are enough changes to warrant it - far more changes that between 5-6-7. However, you'll be amazed how much has stayed the same. The Issue 8 board I have been working on with Nasta is now called Issue X. It is wildly different. That does leave room for an Issue 9 in there, but again that will be a very different board to this one or any previous QL - though a lot more traditional than Issue X.

Other points of note are:
Battery backed RTC
Microdrives fully implemented, with microdrive out too!
Accepts standard membrane
100% Issue 7 compatible, no memory map or timing changes
4-layer board, fully debounced power, clean signals

This is the ONLY 100% original QL board I will make. I am buying the components to make 100 right now. Once the 100 are gone... They're gone.


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Re: What the test points are going on...

Postby Szk » Fri Mar 15, 2019 10:57 pm

Dave wrote:Power in is 9V from a standard 2.1mm power supply. If you have no expansions, a 500mA one will work. If you're going to plug a city of retro electronics into it, you might want a 2 or 2.5 amp 9v adapter. There is a power switch.
Image

Great work Dave!
May I suggest some kind of reverse polarity protection at the power supply jack?
You know, a few Spectrums keep dying because the owner bought a new power supply and forgot to check the plug... :D


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Dave
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Re: QL test points...

Postby Dave » Fri Mar 15, 2019 11:31 pm

The power supply will be added last, once I know exactly what the power requirements are. It will have a bridge rectifier so that no matter the polarity of the supply, damage won't occur. There will also be a DPST power switch, so both lines are switched together.


Nasta
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Re: QL test points...

Postby Nasta » Sun Mar 17, 2019 2:37 pm

Dave wrote:The power supply will be added last, once I know exactly what the power requirements are. It will have a bridge rectifier so that no matter the polarity of the supply, damage won't occur. There will also be a DPST power switch, so both lines are switched together.


Don't use a bridge rectifier as it will have about 1.5V of voltage drop. A single Schottky diode in the right direction will protect the board - and if there is voltage and the QL does not work, that will be a clue to the user the polarity is wrong.
Also, this is the better option for a simple and proper reset circuit, but I will discuss this in private (clue: TL7705 is widely available).


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Dave
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Re: QL test points...

Postby Dave » Sun Mar 17, 2019 3:07 pm

Sometimes idiot-proofing the machine includes protecting it from me ;)


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Re: What the test points are going on...

Postby Whopper » Sun Mar 17, 2019 3:54 pm

Dave wrote:This is the ONLY 100% original QL board I will make. I am buying the components to make 100 right now. Once the 100 are gone... They're gone.


Hi Dave,

So what is the procedure to register interest in one of these boards, ether fully populated or SMD only?

Because I am really interested in one.

Thanks,

Whopper


You woke me for THAT!!!
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Re: QL test points...

Postby belg4rion67 » Sun Mar 17, 2019 4:35 pm

Me too!


Only original hardware! :)
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Dave
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Re: QL test points...

Postby Dave » Sun Mar 17, 2019 6:14 pm

There's no need to register your interest. When they're ready I'll post photos of 50 ready to ship. I'll be doing the assembly and testing myself, as I have the facilities to do that here.



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