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-   -   I found it! A very sorry looking MK14. (https://www.vintage-radio.net/forum/showthread.php?t=170727)

SiriusHardware 27th Mar 2021 11:44 pm

Re: I found it! A very sorry looking MK14.
 
If anyone does have a programmer which can 'do' the Texas SN74S287 then it might be possible to programme an MH74S571 in two passes, with a slight adaptation.

The difference between the two is pin 14 (CE2 on 287, A8 on 571). You could tie pin 14 low to programme the lower 256 nibbles, and then tie pin 14 high to programme the upper 256 nibbles, both times with the programmer set to programme the 256 x 4-bit SN74S287.

Unfortunately my programmer does not offer the SN74S287 either, so I can't try it.

ortek_service 28th Mar 2021 1:14 am

Re: I found it! A very sorry looking MK14.
 
2 Attachment(s)
Quote:

Originally Posted by SiriusHardware (Post 1357998)
Yes, it's been suggested before that the MH devices could actually be programmed using the hardware method and algorithm for the SN (Texas) prefix devices - only trouble is, Texas don't ever seem to have made an SN74S571 so it's not as though you can just choose 'Texas / SN74S571' on your 'western' programmer to programme MH74S571s.

Texas did make a SN74S287, and here is an article about programming those - the author points out what may be a critical difference between the SN and MH devices (roughly 8th paragraph down) so they may not be as directly programmer-compatible as it first seems.

http://randomvariations.com/2014/09/...87-programmer/


Yes, it seems TI were relatively late to Bipolar PROMs (Maybe busy keeping up with Intel on EPROM's), and they never made some of the larger ones.
Although it seems National Semi weren't there first either, with it actually being Harris (Even though they don't seem to be as widely used as others, as well as not as many programmers supporting these): http://www.bitsavers.org/components/...is_Bipolar.pdf
"Harris introduced the industry's first bipolar programmable read only memory (PROM) in 1970, and has continued as a leader in the field of bipolar
PROMs. Harris offers a complete spectrum of bipolar PROMs from 256 bits
to 64K bits. In 1982, Harris became the first supplier of a new family of programmable logic (HPL) featuring patented on-chip testability"

So I wonder if all makes of Bipolar PROM do have on-chip Testability, that National mention in their later DM74S571 datasheet.

Most manufacturers have cross-reference guides with comprehensive list of other manufacturer's types. But they all seem to not mention anything about programming compatibility.


I recall seeing that randomvariations webpage before, where it does seem to indicate that Tesla devices are like National ones in one respect that the bits are all at 0 unless programmed, whereas, TI types appear to start out at 1 (like EPROM's). I know National and some other makes do start out at 0, from ones I've checked, but can't recall what Tesla ones were when I once programmed a couple and haven't current got access to that programmer to check. But I do see that you had said that Tesla ones had been confirmed as also starting with bits at 0, in post 17, here:
https://www.vintage-radio.net/forum/...d.php?t=146388

I've had a play on my older Dataman-48XP programmer , to see what it thinks the blank state should be for the PROM's it supports (Lots of AMD 27S and Philips/Signetics 82S types + a few National DM74S and a couple of TI TBP + Harris HM-66xx ones - Although no MMI or Tesla ones at all).
And all have the blank state as 0, including the TI TBP18S (4bit?) types.
However, the TI TBP28(L/P/S)(2/4)2 8bit ones have blank state of 1 (like it seems the SN74Sxxx ones are)

Strangely the ELNEC-designed Dataman-48Pro range, which supports the Tesla ones, amongst many others, only supported two Phiips/Signetics 82S10(0/1) types)


I have just found this webpage on fusible link proms, with a manual-switches type (I presume you can't over-programme a fuse!) programmer schematic for Signetics ones, and some info - that basically says you need to check specific datasheets for each make (but not really anything about 74S571): https://www.retrotechnology.com/rest...prom.html#data


Attached are about the most comprehensive data I could find on MH74Sxxx ones' the 'net, with some of it from Tesla's website. And looks to contain the programming info that Slothie had attached a translated version of.

ortek_service 28th Mar 2021 2:24 am

Re: I found it! A very sorry looking MK14.
 
Quote:

Originally Posted by SiriusHardware (Post 1358086)
>>
If anyone has a Tesla MH74S287 and a programmer which can natively programme the SN74S287 then it would be great if they could try programming the MH74S287 'as though' it was an SN74S287.

Well as you got it confirmed that Tesla ones have blank state of 0, and would appear that TI SN74Sxxx ones have blank state of 1, then I certainly doubt trying this would work.

And unfortunately, finding programmers from the last 20+ years that support the TI SN74Sxxx ones, seems even more difficult than for Tesla MH74Sxxx.

I've searched the >900 page pdf latest device list of the ELNEC-designed Dataman 48Pro one, that did a Tesla MH74S287 one OK, and that doesn't list any TI 74Sxxx types at all (or any MMI 63xx-xx ones, with only 2 not a common type of Harris ones - So no way of programming those ones I've got, unless they do program the same as AMD/Philips/National equivalents).

Mark1960 28th Mar 2021 6:33 am

Re: I found it! A very sorry looking MK14.
 
Quote:

Originally Posted by SiriusHardware (Post 1357900)
Mark's issue VI has N82S131Ns in it, I would be interested to know if they appear to him to run any cooler than the DM74S571s in his original issue IV. They still run quite warm, but to my mind not as hot as the DMs.

Iíll see if I can find a second power supply so I can set them both up beside each other.

Iíve also added a non contact thermometer to my shopping list in case I feel the need to take more objective measurements.

Looking at the datasheets, the DM74S571 max supply current is quoted as 130mA and typical 90mA at 5.5v, while the 82S131 quotes only the maximum of 140mA at 5.25v. This would suggest the 82S131 would run hotter.

SiriusHardware 28th Mar 2021 9:45 am

Re: I found it! A very sorry looking MK14.
 
That didn't seem to be the case to me, but I will leave that to you to investigate. I do have some more blank 82S131s here but I don't want to programme them for purely whimsical reasons (which probably means they will never be programmed with anything - always the problem - when is code ever important enough, and bug free enough, to commit to one-shot memory devices?). It's a shame no-one ever came up with a pin-compatible Flash version.

Buzby123 29th Mar 2021 12:29 pm

Re: I found it! A very sorry looking MK14.
 
3 Attachment(s)
First attempt at powering Micky's display.

I'm using Vicky to test. Things to note, the display is very dim. ( It looks OK because phone cameras are more sensitive at the red end of the spectrum, but trust me, it's dim ! )

A few segments missing. The display should be '8888 1F'

EDIT : Rusty pins !

Buzby123 29th Mar 2021 1:04 pm

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
I think I need some new digits :(

SiriusHardware 29th Mar 2021 1:48 pm

Re: I found it! A very sorry looking MK14.
 
From experience, you may need a full set because if you replace just some of them the brightness of the new ones will probably be noticeably different. Slothie reckons modern displays produce a lot more light per mA than equivalent displays from 40 years ago.

Going way back to near the beginning of this thread you did say that in your recollection the segments on the big display had always been dim, at the time you seemed to feel that you had possibly not got the display driver design or component values right originally?

Buzby123 29th Mar 2021 2:09 pm

Re: I found it! A very sorry looking MK14.
 
Yes, the display was dim from day one, but I wasn't too bothered at the time. I was fairly certain I could just replace the 150 ohm resistor pack to get a bit more brighness.

However, that's a minor problem compared to the rusted pins.

The displays are FND507, and I'd prefer to replace with the same.

This project is 1 step forward, 2 steps back !. Will I ever get Micky working ?

ortek_service 29th Mar 2021 2:53 pm

Re: I found it! A very sorry looking MK14.
 
I presume you have fitted for IC13, the original 7445 (80mA sink) ?
- rather than the 7442 (16mA sink), that NS used on their Introkit with it's slightly smaller pocket calculator display / keypad or a lower-power version of either.

SiriusHardware 29th Mar 2021 2:57 pm

Re: I found it! A very sorry looking MK14.
 
I think it's possible that Buzby's display driver actually expects there to be a 7442 fitted rather than a 7445 - isn't that what Micky had fitted when it originally emerged from the loft?

It's not just the current output capability, isn't one totem-pole and the other open-collector outputs?

I think, Buzby, that you will still be able to obtain brand new 7-segs with the correct common (Anode? Cathode?) and the exact same pinout but surviving NOS examples of the original FND507 types could very well be dim just due to age even if you can still find them.

I built a Maplin Z80 system in the early nineties, played with it for a while, put it in the loft, got it out ten years later and the 7-segs were all very dim compared to how they had been, despite the system never having been run in the interim. I looked all over for a fault and then finally fitted a set of replacement 7-segs which brought it back up to the original brightness. I have no idea what the failure cause / mode of the original displays was. The replacement ones I fitted are now twice as old as the original ones ever were, and the display is still nice and bright.

ortek_service 29th Mar 2021 3:29 pm

Re: I found it! A very sorry looking MK14.
 
Yes, the 7442 can also source current but not very much - only 0.8mA, compared to its 16mA sink capability. So rather asymmetric, and you'd be unlikely to use it as a high-side driver (Plus it is low-side in the MK14, although you may be able to use some beefier high-side driver gates).
I don't think I've seen a CMOS 74HC42 etc. CMOS pin-compatible version, that would give you better high-side drive. And I presume they didn't bother with an 74L / 74LS in these, if they were design to sink quite bit of current compared to conventional L / LS TTL outputs.


I remember buying some similar looking FND500's, on a Digital capacitance meter EPE project, back in the 80's, and these may be the opposite common polarity. But I never really used it, as never found it worked too well (maybe because they said you had to use the Mullard version of the Display-counter IC, whereas I'd bought cheaper Motorola one - although I did at least mod their circuit to produce a proper square-wave clock into it)

SiriusHardware 29th Mar 2021 5:32 pm

Re: I found it! A very sorry looking MK14.
 
I've just realised that Buzby's original displays effectively have a built-in bezel / red filter so that's understandably why he wants to source some similar ones.

ortek_service 29th Mar 2021 5:37 pm

Re: I found it! A very sorry looking MK14.
 
Yes, the FND500 I got, also had this, looking very similar.
I seem to recall I got them (new) for only around 20p each from Sendz Components (surplus TV parts supplier), but may have been from Greenweld / Cricklewood etc.

SiriusHardware 29th Mar 2021 5:51 pm

Re: I found it! A very sorry looking MK14.
 
I found some of Buzby's original type with an online seller who Tim and I have both independently used before, I've sent Buz a PM about them.

Buzby123 31st Mar 2021 11:53 am

Re: I found it! A very sorry looking MK14.
 
Quote:

Originally Posted by SiriusHardware (Post 1359146)
This repair may cost you a bit more yet, ... It all adds up.

Don't I know it :(

SiriusHardware 31st Mar 2021 5:46 pm

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
Another little step forward for the project, a DM74S571AN arrived from Buzby today, so... (image).

To be honest I'm posting this partly to cover my own rear exit, because Buzby's original SOC-supplied IC2 (marked '1o', offset to one side upper right of the picture) died not ten running hours after it was originally working here. So here is proof that the original IC3 and the replacement IC2 were working on this day. I couldn't find a newspaper headline to include in the shot. ;)

I ran these for about an hour and a half in my original MK14, because that machine has the regulator mounted offboard on a substantial heatsink whereas my issue VI replica only sports a skimpy little black number.

One thing I did notice is that the original IC3 (Non-A version, large label on top) runs hotter than the replacement IC2 ('A' version, no label) so I would suggest using small labels like the sticky 'dots' SOC originally used on these new-OS PROMs and placing them at one end of the IC rather than over the middle, which is where SOC originally put them.

We can now add the DM74S571AN to the list of specific devices known to have been tested in the MK14.

Buzby123 31st Mar 2021 6:13 pm

Re: I found it! A very sorry looking MK14.
 
Quote:

Originally Posted by SiriusHardware (Post 1359227)
.. To be honest I'm posting this partly to cover my own rear exit, because Buzby's original SOC-supplied IC2 (marked '1o', offset to one side upper right of the picture) died not ten running hours after it was originally working here. So here is proof that the original IC3 and the replacement IC2 were working on this day. I couldn't find a newspaper headline to include in the shot. ;) ...

Don't worry, I'd have trusted you if you just said 'it works'.

The the original PROMs you tested for me worked fine when I received them back, but one stopped working the next day. That's just my luck, which still hasn't changed. ( Today, the original bubble display I salvaged last week decided to lose a segment !. )

Quote:

... original IC3 (Non-A version, large label on top) runs hotter than the replacement IC2 ('A' version, no label) ...
I didn't notice the new one was an 'A' version. Is there a significant difference ?.

Cheers,

Buzby

SiriusHardware 31st Mar 2021 6:15 pm

Re: I found it! A very sorry looking MK14.
 
Speed.

But the non-A version is fast enough, so the 'A' version is more than fast enough. No difference between them from the MK14's point of view.

SiriusHardware 31st Mar 2021 7:05 pm

Re: I found it! A very sorry looking MK14.
 
I suggest you save your life at regular intervals, and then when bad things happen you can just go back to an earlier save.

Quote:

the original bubble display I salvaged last week decided to lose a segment !
Is that

-One segment of just one cell?

-The same segment in all of the cells?

or

-One whole cell off?


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