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Old 4th Mar 2023, 1:09 pm   #141
SiriusHardware
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Default Re: Idiot building a MK14 thread

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All chips inserted with the exception of the 8154 (U8) and the two ram chips (U5 and U7) closest to the keyboard...?
Indeed yes. This is so that in the event of some horrific calamity you will fry three less expensive / hard to find chips than you would otherwise.

The MK14 kit originally only came with two of the maximum four RAM ICs and without the 8154 which was also an optional extra, so it will run perfectly well without those optional chips.

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Old 4th Mar 2023, 3:55 pm   #142
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Default Re: Idiot building a MK14 thread

Partial success...

Colin.
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Old 4th Mar 2023, 3:58 pm   #143
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Default Re: Idiot building a MK14 thread

Ah. With the other two RAM chips and the 8154 plugged in it looks a lot better.
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Old 4th Mar 2023, 4:14 pm   #144
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Default Re: Idiot building a MK14 thread

I think you must have put the first two RAM chips in the wrong slots. Putting the full set in fixed it.

The 8154 won't have had any effect, as it's not involved in running SCIOS.

So now we have another MK14 user !
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Old 4th Mar 2023, 4:15 pm   #145
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Add one to the number of MK14s in the world.

Thanks to all who generously helped me with this.

Cup of tea time.

Colin.
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Old 4th Mar 2023, 4:26 pm   #146
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Default Re: Idiot building a MK14 thread

That 'failure' on first switch on must have been a heart stopping moment for you. Glad to see it working in the end.

I was wondering if we (experts that we all are) managed to tell you the wrong pair of RAM ICs to plug in and to leave out - it's an error which has been made at least twice in the past. I did actually consider this and tried several times to look back and see whether we had advised you correctly but I got distracted every time.

So now that I finally did look, see this post by Slothie:-

https://vintage-radio.net/forum/show...&postcount=648

Now that post seems to say that the ones nearest to the PROMs are the ones which MUST be fitted. I'll have to try this myself.

Regardless, you've managed to get it working which is a relief.
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Old 4th Mar 2023, 6:11 pm   #147
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First set of temperature readings after 40 minutes. Powered on, loaded Sirius' "Colin's" program and left it switched on/running.

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Old 4th Mar 2023, 6:35 pm   #148
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Very interesting, and straight away you can see why I don't put the paper dots on the centre of the PROMs. It's also interesting to see that one runs a bit hotter than the other and I assume that is because they don't both have exactly the same number of fuses blown.

Can you tell us a bit more about the camera? I've seen you playing with it over on VCFED as well. There is a recurring fault that I get at work where one of many ceramic capacitors across a supply line fails low resistance. At the minute I find the guilty one by putting a high current supply on the rails to make it heat up, but one of these days I am going to lose my fingertip while 'detecting' which one has failed.

It's also interesting that the 7445 runs quite warm but it is an 'original', not LS, IC and it handles the common current for all of the 7-segment display cells.
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Old 4th Mar 2023, 6:42 pm   #149
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It's a Topdon TC001 which plugs into my android phone using the USB-C port. I'm still learning how to use it really, but it's good for this kind of thing as you can tap on the screen for it to show the temperature wherever you want.

Colin.
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Old 4th Mar 2023, 9:13 pm   #150
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Default Re: Idiot building a MK14 thread

The 7408s look like they might be warm too, but hidden behind the display module.

Interesting that the pins on the ICs stand out as being a lot cooler than the chip itself. That might be because they are in thermal contact with the socket and the pcb, or just that they radiate and conduct heat to the air better than the plastic body.
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Old 5th Mar 2023, 10:12 am   #151
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I did have a brief look at the TC001 - a little bit out of my price range to be able to justify a purchase unfortunately. I did notice that there are 'toy' versions, basically a bare PCB and display sandwich, available from China for about a fifth of the price. When I have more time I'll look at a few reviews for those.

I must say Colin got the hang of entering and running programs really quickly, it was often stated in the past that the MK14 manual wasn't very accessible for beginners and I was expecting we'd have to give a brief summary of how to enter, look through, edit and run programs but Colin got off to a flying start.

In those days the MK14 was all we had so we didn't have the luxury that we have nowadays of writing / preparing / storing code on a 'big' computer and then sending it to the MK14, so that's possibly the next step, assembling some sort of upload system to make it easier to play with the MK14.

If you wanted to be truly old-school you could build a cassette tape interface - just a couple of CMOS ICs and a handful of other components - or - write some Arduino code to receive the digital 'save' data from the MK14 and play it back into the MK14 without actually converting it to / from audio.
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Old 5th Mar 2023, 7:11 pm   #152
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Default Re: Idiot building a MK14 thread

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Originally Posted by ScottishColin View Post
Add one to the number of MK14s in the world.
Hi Colin, great to see that all up and running. The thermal image is impressive too. I'm using AMD PROMs and they get warm but not 49 degrees I wouldn't have thought (radiator temperature!).

Somewhere in a box of boxes I have a thermal camera that was being binned at work because someone had connected the wrong supply to it and apparently fried it. So I reclaimed it from the bin (if only for the IR lens). It turned out the 5V reg has been damaged but other than that still working. If I can locate it I'll see if I can do a similar thermal capture.

(Maybe we should have a thread dedicated to items binned at work, or similar, that were salvaged and repaired. Would make for interesting reading. I know SiriusHardware has mentioned some in the past).
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Old 5th Mar 2023, 7:27 pm   #153
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Default Re: Idiot building a MK14 thread

Parts galore, some of which (like the PIC16F876As which went to Phil recently) have been distributed on to forum members. I've also just recently acquired a couple of decent EPROM programmers from work - not broken, just no longer wanted.

I have one pair of AM27S13s which I bought from Kan_Turk specifically to verify that they did work in the MK14 as expected (they do, of course) and it is my impression that they run slightly cooler than the original DM74S571s or the Philips/Signetics N82S131N both of which run alarmingly hot - if any other chip - with the possible exception of a Sinclair ULA - was running at that temperature you would automatically assume it was duff (but that was always the case with the DM devices, so I wasn't surprised to find that the Philips devices ran hot as well).

I've never seen Tesla MH74S571s up close but I would imagine they get quite toasty as well. I have some on the way, so I'll soon find out.
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Old 5th Mar 2023, 11:52 pm   #154
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Default Re: Idiot building a MK14 thread

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>>
if any other chip - with the possible exception of a Sinclair ULA - was running at that temperature you would automatically assume it was duff (but that was always the case with the DM devices, so I wasn't surprised to find that the Philips devices ran hot as well).

I've never seen Tesla MH74S571s up close but I would imagine they get quite toasty as well. I have some on the way, so I'll soon find out.
It seems a few IC's ran rather warm in the Commodore 64 - like their own 'MOS' Mask-ROM's and the Address-decoder Logic-Array (that ran hotter than the original Philips OTP PLA, they'd made a mask-programmed copy of), and so quite-often failed. (E)PROM's being used to replace these, usually run virtually cold.

Although I have some MH74S571's, to use for the MK14 PROM's, I've not got the (2/9)111 SRAM's (or made a 2114 etc adaptor) to complete it yet. But Chris probably has some to try in his.
We've got access to some IR Cameras, but probably enough to just tape one of those RS etc miniature type-K thermocouples to each of the IC's and plug them into the Fluke 2-ch thermocouple-thermometers we've got.


BTW, When I first saw that display with the missing segments, I thought there might be an open-circuit display segment connection. As I wouldn't have expected it to run at all without the system-workspace RAM in the Map.
- Might have to see what mine does, without any RAM fitted.
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Old 6th Mar 2023, 11:11 am   #155
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It seems a few IC's ran rather warm in the Commodore 64 - like their own 'MOS' Mask-ROM's and the Address-decoder Logic-Array (that ran hotter than the original Philips OTP PLA, they'd made a mask-programmed copy of), and so quite-often failed. (E)PROM's being used to replace these, usually run virtually cold.
Colin posted some thermal shots in another forum of his famous PET, where it so happens that one of the original ROMs has been replaced with a EPROM substitute. As you say, the EPROM runs far cooler than the original mask ROMs.
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Old 8th Mar 2023, 11:55 pm   #156
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Quote:
Originally Posted by SiriusHardware View Post
>>
If any other chip - with the possible exception of a Sinclair ULA - was running at that temperature you would automatically assume it was duff (but that was always the case with the DM devices, so I wasn't surprised to find that the Philips devices ran hot as well).

I've never seen Tesla MH74S571s up close but I would imagine they get quite toasty as well. I have some on the way, so I'll soon find out.
>>
Although I have some MH74S571's, to use for the MK14 PROM's, I've not got the (2/9)111 SRAM's (or made a 2114 etc adaptor) to complete it yet.
But Chris probably has some to try in his.
We've got access to some IR Cameras, but probably enough to just tape one of those RS etc miniature type-K thermocouples to each of the IC's and plug them into the Fluke 2-ch thermocouple-thermometers we've got.
>>
I asked Chris earlier today, if he'd tried the Tesla PROM's yet in an MK14, to see how hot they got. And he told me he'd found his original MK14 replica drew the same supply-current with Tesla PROM's fitted, as with NS ones.

So it would appear these must run at the same temperature, assuming the same DIL package material - Not sure if ceramic ones would run at a much-different temperature to standard 'plastic' epoxy (even if ceramic has better thermal conductivity, you would need something thermally-conductive against it, to heatsink it. Plus I can't see there being much difference of the convection to surrounding air, which is probably quite poor without some fan-assistance effectively increasing the surface area).
And I doubt there's too much thermal-conduction through the lead-frame, with only a single ground pin - As standard DIL IC packages weren't really designed for much power-dissipation. But I wonder if the 'die-paddle' inside the package has some extra heat-spreading metal fins to the ends of the package (If datasheets don't give details, maybe one's been X-rayed or a dead one etc had the top removed - Often easier on old 2-part ceramic packages)

I suppose you could always add some small DIL-IC heatsinks to the top of the PROM's, using thermally-conductive D/S sticky pad material so that they could be removed again more-easily than thermally-conductive epoxy etc.
As many IC's even in modern computers often require these, with kits sold for the RPi4 and DRAM DIMM's sometimes having metal heat-spreading plates over the top of the IC's.


Graham: I wonder if your AM27S13s were in a different package / have some extra thermal-spreading metal inside? Or maybe measuring supply-current with these PROM's fitted, might reveal if they do actually draw less power than most of the others.

Last edited by ortek_service; 9th Mar 2023 at 12:03 am.
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Old 9th Mar 2023, 12:05 am   #157
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My 27S13s are in plastic, not ceramic packages. The easiest way to measure up would be to put them in my original MK14 because the regulator on that is offboard and it's easy to break into the 5V supply to measure the current.

Unfortunately with the issue VI being much more functional and usable than my original machine, not to mention the original machine now being a fragile, priceless historic artefact, I tend to keep that mothballed nowadays so I'm not sure when I will next get the opportunity to make that measurement.

Of course I could just look at the difference in the current drawn from 7.5V by the issue VI with the AMD PROMs in / with other PROMs in. That would tell us something, relatively speaking. I know that when I have done measurements in the past I have estimated that the two DM74S571 PROMs alone draw about 200mA+ between them.
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Old 9th Mar 2023, 1:07 am   #158
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It shouldn't really matter whether it's current into the 7805 regulator (I believe that's all Chris measured, as quite easy to do when powering the board from a reasonably-good bench PSU with built-in digital current display to 1mA resolution / inserting any DMM with a 2A current-range in series) or the +5V output from it.
They should be virtually the same (Only a few mA's 7805 ground-current) if everything's +5V-powered on this.
- And you're only really looking if there's much difference in total power consumption, when running under the same conditions with only the PROM's swapped.
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Old 9th Mar 2023, 1:14 am   #159
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Don't forget, one of the NS databooks shows a circuit to power-down the PROM when it's not addressed, specificaly to reduce power consumption, and heat as well. ( I can't find it, but it's on the forum somewhere. )

It might be a neat option to have on the MK14E.
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Old 9th Mar 2023, 1:40 am   #160
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Chris has deliberately designed-out these getting hard-to-obtain / program Bipolar PROM's on his MK14E, replacing these with a single small-capacity 2716/2732 8bit EPROM. (Also now rather obsolete, but these are still fairly easy to obtain NOS / erase old used ones, unlike OT-PROM's, and many of us have already accumulated a good collection of these)

And EPROM's do usually run fairly-cool (Plus can get 27C16 / 27C32 CMOS ones, for even lower power) - especially compared to rather high-power high-speed Bipolar PROM's - so no real need to try and power these down / already power-down when their nCS Chip-select input is not active.

Last edited by ortek_service; 9th Mar 2023 at 1:46 am.
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