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Old 4th Nov 2022, 4:07 pm   #41
SiriusHardware
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Default Re: MK14 Rev VI PCBs

Can I suggest that anyone needing specific bits for a replica asks here on the forum first, just on the off chance? Even if we don't have them in our bits boxes we may know where to get them. Slothie's original epic thread 'MK14 schematic revisions' contains dozens of useful links and bits of information, but I admit they can be hard to find as it is a huge thread.

I have a few original type MK14 reset switches here in black and red. Coolsnaz2 could have had one if only I had known he needed one. I've also got a bubble display which was kindly given to me by Tim(bucus) at some point in the past - actually he gave me two but I am holding one as a spare against the possibility of the display on my original or replica MK14 failing.

Farnell do a suitable flat, stiff, short 0.1" spaced ribbon cable - it's 20 way rather than 18 way but it is easy to trim two of the 'ways' off one edge. This is what is between my bubble display and my issue VI. These ribbons aren't stiff enough to support anything heavier than a bubble display on their own but you could parallel two of them up, glued front against back, to make a single stiffer ribbon.

https://uk.farnell.com/te-connectivi...y-1/dp/1310365
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Old 4th Nov 2022, 4:35 pm   #42
Realtime
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Default Re: MK14 Rev VI PCBs

Quote:
Originally Posted by coolsnaz2 View Post
I also purchase 8 Digit 7 Segment Module MAX7219 from Amazon
How are you driving the MAX7219 display? Are you removing the 7219 chip and wiring to the back of the board or disabling the chip perhaps?
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Old 4th Nov 2022, 5:23 pm   #43
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Default Re: MK14 Rev VI PCBs

Realtime

I am removing the chip and wiring each segment and each digit to the connector. I can switch between using the 7 Segment module or the bubble display.
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Old 4th Nov 2022, 6:04 pm   #44
SiriusHardware
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Default Re: MK14 Rev VI PCBs

That is quite an ingenious way of obtaining a multiplexed 7-segment display for not much money.

Until quite recently it used to be possible to buy basic LED calculators (of the type sold by Woolies in the late seventies) for a couple of quid, especially if they had a broken or missing key or two. The Texet 880 is one example which has an MK14 compatible display.

Last I looked, they had suddenly shot up to about £20 or more so they are no longer the cheap sources for displays that they used to be.
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Old 4th Nov 2022, 6:39 pm   #45
Mark1960
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Default Re: MK14 Rev VI PCBs

Does anyone other than Colin need 8060 or 8154 to complete the build?

Sirius suggested putting together a single shipment to UK to be redistributed, though this carries a risk on the higher customs declaration of becoming subject to vat and therefore also customs handling charges. The vat is not so bad but the handling charges can be a bit of a pain. Also with higher value it might be best to add tracking which is quite a big jump on shipping to about $65 instead of only $12.

I also have extra bubble displays, which I think are liteon, checked out with a multimeter lighting segments to match the mk14 pinout, and reset switches in yellow, white, red, green or dark grey.
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Old 4th Nov 2022, 7:32 pm   #46
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Default Re: MK14 Rev VI PCBs

I'd better say that my spare bubble display has already been asked for, but not by Colin (mine will be passed on FOC just as it was from Tim to me).

If Colin needs one as I think he will, maybe Tim has more of the ones he gave to me - if not then Colin may need a display from you (Mark) in addition to the two forty-pinners.

I have a feeling Colin, being a sensible sort, will probably want to have a PCB in front of him before he starts spending money on parts to go into it.
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Old 4th Nov 2022, 7:49 pm   #47
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Default Re: MK14 Rev VI PCBs

I’ll pm colin sometime over the weekend after I have a chance to check my stocks of some of the other more common chips that it might be worth including if he doesn’t already have them.
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Old 4th Nov 2022, 7:51 pm   #48
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Default Re: MK14 Rev VI PCBs

Quote:
Originally Posted by SiriusHardware View Post
I'd better say that my spare bubble display has already been asked for, but not by Colin (mine will be passed on FOC just as it was from Tim to me).

If Colin needs one as I think he will, maybe Tim has more of the ones he gave to me - if not then Colin may need a display from you (Mark) in addition to the two forty-pinners.

I have a feeling Colin, being a sensible sort, will probably want to have a PCB in front of him before he starts spending money on parts to go into it.
You're a mind reader.

Colin.
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Old 6th Nov 2022, 1:36 am   #49
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Default Re: MK14 Rev VI PCBs

I think I still do have 1or 2 bubble displays left so no issue there.
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Old 6th Nov 2022, 3:21 pm   #50
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Default Re: MK14 Rev VI PCBs

Quote:
Originally Posted by Realtime View Post

(I hope Sloathie is OK with that - it's his creation after all).
Totally OK with this. I created it because there was no "open source" PCB available (and I wanted an MK14!).

Ian
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Old 6th Nov 2022, 3:29 pm   #51
Slothie
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Default Re: MK14 Rev VI PCBs

I also wrote a "construction manual", can't find the link to the original post but here it is.
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File Type: pdf MK14_Issue6_1r2.pdf (977.3 KB, 83 views)
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Old 8th Nov 2022, 4:27 pm   #52
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Smile Re: MK14 Rev VI PCBs

Quote:
Originally Posted by Slothie View Post
I also wrote a "construction manual", can't find the link to the original post but here it is.
Clearly a mind reader, was about to post see if such a thing existed
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Old 8th Nov 2022, 6:53 pm   #53
SiriusHardware
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Default Re: MK14 Rev VI PCBs

I've just read through the document again - a very nice manual which covers a lot of ground and contains a lot of detail.

Since it was written I have had the opportunity to try both AMD 27S13 and 27S13A PROMs which are described as likely to work but untested, I can confirm that they definitely do work, as do DM74S571AN - as you might expect, they are just faster versions of the 'plain' DM74S571N.

Looking at the PCB overhead view you will notice that Slothie has placed a 'cartoon bubble' indicating the type of device to fit in the U11 position, that is because on the PCB itself there was a small placement problem which led to the screen printed U11 and 74LS365 labels overlapping, making them hard to read. When U11 is fitted, the overlapping labels are completely hidden by U11.

On the PCB overhead diagram the polarity of the reset capacitor C6 is shown correctly but on the actual PCB this detail is missing, so orient C6 as per the overhead diagram in Slothie's document.

Slothie mentions potential key bounce problems with cheap ebay sourced tact switches, mine has Omron branded low Newton force switches (sourced from Farnell) fitted and I can't recall a single incidence of switch bounce in the many hours that mine has been in use for now. The cheap switches sometimes suffer from another problem, the heads have a tendency to be able to rotate +/- a few degrees clockwise or anticlockwise making the keys look a bit higgledy piggledy, the Omron switches have very little rotational movement.

The tact switches are of a type which can optionally have clear plastic covers snapped over the key caps and this provides an easy way of legending the keys. Notice the keypad diagram on page 12 of the document - this does not merely show you the relative layout of the keys. If you print that page correctly scaled, you can cut those key legends out and fit them under the clear key caps. The inside dimension of the clear key caps is 10mm x 10mm.
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Old 8th Nov 2022, 7:56 pm   #54
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Default Re: MK14 Rev VI PCBs

For those of us with 3D printers, some keyboard files here (which Slothie has commented on):

https://www.thingiverse.com/thing:4722770

Colin.
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Old 8th Nov 2022, 9:25 pm   #55
SiriusHardware
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Default Re: MK14 Rev VI PCBs

Interesting find which I was not aware of, thanks - anyone whose keys do tend to rotate would find that keypad frame just the thing to keep all of the keys smartly lined up.
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Old 8th Nov 2022, 9:44 pm   #56
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Default Re: MK14 Rev VI PCBs

That one looks like its designed for a flat printed overlay over tactile switches with round buttons.

I find the one I built with keycaps and clear covers a bit wobbly, maybe a keycap guide would help. The second one I built using low profile tactile switches and feels better, but could do with a labelled overlay, though I seem to have become used to memorising the key layout. I really should get a downloader built up with Slothie’s pcb that Sirius sent me.
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Old 10th Nov 2022, 11:05 am   #57
Slothie
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Default Re: MK14 Rev VI PCBs

I made a keyboard cover for the MK14 also, just never published it anywhere. Here it is for those interested (zipped .STL file, because the forum doesn't allow bare STL files). Note that this frame works for the type of key that has clear covers (the holes for keys are 12mmx12mm which is a tiny bit bigger than the outer dimension of the clear covers). It also has a small cutout to make room for C16 which is very close to the keyboard.
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Old 10th Nov 2022, 11:17 am   #58
SiriusHardware
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Default Re: MK14 Rev VI PCBs

I would be interested in one of those in black and expressed an interest via PM when you first mentioned them, but I think you were otherwise occupied at the time. I'm still interested, though.
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Old 10th Nov 2022, 1:32 pm   #59
Slothie
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Default Re: MK14 Rev VI PCBs

Quote:
Originally Posted by SiriusHardware View Post
I would be interested in one of those in black and expressed an interest via PM when you first mentioned them, but I think you were otherwise occupied at the time. I'm still interested, though.
I have a few problems getting stuff posted at the moment but I'm working on it.....
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Old 10th Nov 2022, 3:07 pm   #60
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Default Re: MK14 Rev VI PCBs

Are any more boards available or if not are the gerber files available as I might be interested in one.
I understand the rev VI has the address and data busses already wired for the VDU is that correct?

It might also be useful to get a list of reliable parts suppliers together as virtually all of the old parts from China are recycled / remarked and I have had variable results with many non-functional parts which doesn't matter so much when they are 10 for a $1 but perhaps is more important for the more expensive parts
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