Idiot building a MK14 thread

[Realtime]

You'll need to fit the 4MHz crystal to use RealView (or any other VDU module) as it sets the correct pixel clock rate. You can still run the MK14 without a VDU, just means the processor is running 4/4.43 = 90% of the 'normal' speed. In most cases you won't notice the difference.

[ScottishColin]

I've dug and I actually have both but I'll fit the 4Mhz.

Colin.

[ScottishColin]

Right. That's everything fitted except the ICs and the display.

Once the power supply turns up (tomorrow) are there any tests I can do without the display/ICs fitted?

I have ordered the FSN-21A-20 cable but it'll take a little while to turn up. Not paying a tenner postage/picking fee plus VAT from Farnell.

Colin.

[SiriusHardware]

Reasons to fit 4.43 - certain programs such as 'music box' use software timing and the notes won't sound right if 4MHZ is used. Historically it was only changed to 4.00 if a vdu was used because the SOC vdu stole its clock signal from the MK14, I'm not sure if Realview does that though.

[SiriusHardware]

About the only power test you need to do is to fit the regulator, power up the board with no ICs fitted and just make sure that the output from the regulator is 5V as expected.

[SiriusHardware]

I'm not sure if Realview does that (takes its clock from the MK14) though.

Sorry, I didn't read back far enough to see that Realtime had confirmed that it does.

[Mark1960]

For the display you should note there are 18 pins on the board but only 17 on the display. The left most pin 1 is not connected to the display. I have mine buit using a 17 male pin header on the board and a 17 pin female header on the display, bending the connections on the female header to approx 45 degrees before fitting to the display to avoid any stress on the display module.

You can socket the crystal and then choose which one you want to use.

I noticed your tactile switches don’t have locating pips to fit the holes in the board, so if you are using the square button type you probably want to check they are fitted square before soldering.

[SiriusHardware]

I have ordered the FSN-21A-20 cable but it'll take a little while to turn up.

Are you able to say where you managed to find it with more reasonable carriage costs? This may be useful for anyone else trying to build one to know - but don't worry if you don't feel at liberty to say.

The flexy ribbon cable you've ordered can be bent into various shapes but then stays in that shape so you can (within reason) tweak it for the ideal viewing angle.

The display on my original MK14 on the other hand uses a scheme more like Mark's although mine has a straight pin row connector soldered into the MK14 PCB, a right angled pin row connector coming out from the rear of the display and then downwards, and finally a pair of SIL socket connectors with their through-hole pins soldered together to form a 45 degree 'joiner' with female connectors on each end. One end of this plugs onto the pin row connector on the MK14, the downward facing pins on the display plug into the other end of the 45-degree joiner.

This is OK but you would be surprised how annoying it is not to be able to alter the angle of the display occasionally, as those bubble displays have quite a narrow vertical viewing angle.

[ScottishColin]

Sure.

The £2.33 part from Farnell ended up at £14.74 after adding £9.95 handling charge and £2.46 VAT.

I ordered from Amazon. Granted the cable was £6.60 and postage £3.30 so still £9.90.

It's still a lot for a 1 inch connector, but the £9.95 handling charge and adding VAT to the handling charge got my goat.....

Colin.

Originally Posted by SiriusHardware

Are you able to say where you managed to find it with more reasonable carriage costs? This may be useful for anyone else trying to build one to know - but don't worry if you don't feel at liberty to say.

[SiriusHardware]

Yes, that still seems expensive. I was wondering if you had maybe found it for a better price in one of the usual places. Mine actually did come from Farnell but then I had the benefit of being able to order through work where there always used to be enough orders placed for the whole lot together to qualify for free delivery.

[ScottishColin]

OK - variable power supply is here. I selected 7.5V which measured as 7.73V on the plug.

Plugged into the IC-less board, I get 7.73V on the input leg and 5.074V on the output leg.

Colin.

[SiriusHardware]

Good enough. That 5.074V will probably sink a little bit once there are some ICs running on it.

[Mark1960]

Originally Posted by ScottishColin

OK - variable power supply is here. I selected 7.5V which measured as 7.73V on the plug.

Plugged into the IC-less board, I get 7.73V on the input leg and 5.074V on the output leg.

Colin.

What’s the current rating of the power supply?

[ScottishColin]

2A.

Here's the item in question - hope the mods are ok with the link.

https://www.amazon.co.uk/dp/B08L3HD4MR

Colin.

Originally Posted by Mark1960

What’s the current rating of the power supply?

[SiriusHardware]

Looks OK on paper, nice and powerful if the 2A rating is to be believed.

It will be a switched-mode type but then virtually every modern one is.

The unusual adaptor which breaks the output out to screw terminals could be quite useful for general hobby electronics use.

[SiriusHardware]

Returning to how the display is connected, this shows how I did mine with the upper end of the connector strip approaching the display from behind.

[Mark1960]

Not sure if it makes much difference but my Issue IV has the ribbon cable into the front face of the display module. Did the original assembly instructions advise any particular method?

[SiriusHardware]

Attached, the relevant manual section clearly showing the ribbon approaching the display from the front side as yours does.

The original ribbon was a bit shorter than these 1" strips from TE-Connectivity, which was OK because the keypad (also shown) had a very low profile so the display didn't need to be raised up much.

On the issue VI I was conscious that the keypad (being comprised of proper switches) would be a lot 'taller' and the display would therefore need to sit a bit higher. The decision to thread the cable in from behind on the issue VI build was just what I did at the time. Although I still have the original display for my issue II it has not been directly connected to the PCB since the late seventies, it spent a long period extended off the PCB via flying wires while I tried the machine in various enclosures, and then when I 'restored' it to as close to single board configuration as possible about 12 years ago I remounted it with an angled plug and socket, similar to what you've done on your issue VI.

[ScottishColin]

Counting the wires there, I can only see 16 - is that right?

Colin.

Originally Posted by SiriusHardware

Attached, the relevant manual section clearly showing the ribbon approaching the display from the front side as yours does.

The original ribbon was a bit shorter than these 1" strips from TE-Connectivity, which was OK because the keypad (also shown) had a very low profile so the display didn't need to be raised up much.

On the issue VI I was conscious that the keypad (being comprised of proper switches) would be a lot 'taller' and the display would therefore need to sit a bit higher. The decision to thread the cable in from behind on the issue VI build was just what I did at the time. Although I still have the original display for my issue II it has not been directly connected to the PCB since the late seventies, it spent a long period extended off the PCB via flying wires while I tried the machine in various enclosures, and then when I 'restored' it to as close to single board configuration as possible about 12 years ago I remounted it with an angled plug and socket, similar to what you've done on your issue VI.

[ScottishColin]

I was going to design and print some key-caps to put on top of the switches. The plan (such as it is) is to get them to fit inside the keypad bezel that I have printed already.

Is that of any value to me/others - or do they already exist?

Colin.