TREND SK 947 (Z80) Computer board - UK Vintage Radio Repair and Restoration Discussion Forum

ortek_service · 28th Nov 2022, 2:31 am

A board with a Z80 (CPU + PIO +CTC) & M58725 = 6116 SRAM according to: https://pcbjunkie.net/index.php/reso...eference-page/
- And also a 2716 EPROM ('BOB2' labelled, Binary-file Readout attached, zipped-up)
(BOB = Break Out Board??) and contains a small block with text strings: TED BELOW. [INT][EXT]**** DK0MFSB TMP

From the type number prefix 'SK' - For "Sketch"? (sometimes used in the past on development pre-release drawings) - I'm wondering if this was a prototype?
As solder-resist mask is rather sloping away at an angle at the edges, the 4 holes look rather roughly-drilled and there's many long link-wires + a couple of resistors added to the underside. And also a couple of PCB 'Test Pins'? added afterwards.
Plus the Plated Thru Holes for several IC's & PL1-4 DIP-34 connectors have never been soldered-to. Only 7 wires out of 24 on the ribbon cable from the SKT1 DIL-24 header have been left uncut beyond it.

I can't find anything from Trend back around 1980/81 date of IC's on this, although I do recall the name (I think more recently there is a PC Peripherals manufacturer of that name).

So I'm wondering if anyone recognises this / knows what it might have been used for? - I guess it might be possible to run the firmware through a software emulator / debugger system, like MAME that was done on the Infotron board I'd found or IDA-Pro etc Rev Eng tools.

TonyDuell · 28th Nov 2022, 4:24 am

I've come across various Trend products including optical paper tape readers (IMHO the best designs I've ever used) and datacoms test equipement (test signal generators, RS232 breakout boxes/testers, synchronous serial testers, etc). Maybe something to do with the latter?

ortek_service · 28th Nov 2022, 6:40 am

Thanks for the info on Trend. I wasn't getting much luck with Googling it, as "Trend" came-up so many times in various computer publications.
But eventually I discovered an advert for "Trend-DLC" in a 1981 ComputerWorld issues, and have found a picture of some Trend-DLC equipment (with rather similar double horizontal lines above and below the name) in a picture on the Altair Groups.io forum (but very little else out there):
https://s3-us-west-1.amazonaws.com/g...141blob.jpg%22

I did wonder if my board may be something to do with serial-comms, as the main (only-fitted) X1 crystal is a special 2347.81kHz. But there aren't any dividers on the board, so I guess this goes straight to Z80 CPU (& CTC?).
And there's no UART's or 25pin (only Not-fitted 34way) connector headers on it - But maybe one of the three DIL24 or the DIL40 Not-fitted parts were intended to be UART's etc.

There is a space for a large 'TC1' trimmer-capacitor?, so that might have been for an RTC IC's crystal-tuning - Although there is a couple of close-together holes marked X2 at the front that may have been for a 'Watch' crystal type package.

ortek_service · 28th Nov 2022, 7:13 am

With a bit more trial & error searching, I discovered that the 2.34781MHz frequency was used by some (older?) 'Trend' Telegraph & Data Message Generator equipment that was used by the RAF, on this Air Publications (AP) etc. documents website:
https://www.blunham.com/Radar/APlist.html

And some pictures of this, with the same double-lines above/below "TREND" can be seen in a few Google images, by searching: https://www.google.com/search?q=Tren...x2CL-Foi8RHmqM

So may well be used in something like those (I haven't found any insides-photos yet)

28th Nov 2022, 4:24 am	#2
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 4,736	Re: TREND SK 947 (Z80) Computer board I've come across various Trend products including optical paper tape readers (IMHO the best designs I've ever used) and datacoms test equipement (test signal generators, RS232 breakout boxes/testers, synchronous serial testers, etc). Maybe something to do with the latter?

28th Nov 2022, 6:40 am	#3
ortek_service Heptode Join Date: May 2018 Location: Northampton, Northamptonshire, UK. Posts: 765	Re: TREND SK 947 (Z80) Computer board Thanks for the info on Trend. I wasn't getting much luck with Googling it, as "Trend" came-up so many times in various computer publications. But eventually I discovered an advert for "Trend-DLC" in a 1981 ComputerWorld issues, and have found a picture of some Trend-DLC equipment (with rather similar double horizontal lines above and below the name) in a picture on the Altair Groups.io forum (but very little else out there): https://s3-us-west-1.amazonaws.com/g...141blob.jpg%22 I did wonder if my board may be something to do with serial-comms, as the main (only-fitted) X1 crystal is a special 2347.81kHz. But there aren't any dividers on the board, so I guess this goes straight to Z80 CPU (& CTC?). And there's no UART's or 25pin (only Not-fitted 34way) connector headers on it - But maybe one of the three DIL24 or the DIL40 Not-fitted parts were intended to be UART's etc. There is a space for a large 'TC1' trimmer-capacitor?, so that might have been for an RTC IC's crystal-tuning - Although there is a couple of close-together holes marked X2 at the front that may have been for a 'Watch' crystal type package.

28th Nov 2022, 7:13 am	#4
ortek_service Heptode Join Date: May 2018 Location: Northampton, Northamptonshire, UK. Posts: 765	Re: TREND SK 947 (Z80) Computer board With a bit more trial & error searching, I discovered that the 2.34781MHz frequency was used by some (older?) 'Trend' Telegraph & Data Message Generator equipment that was used by the RAF, on this Air Publications (AP) etc. documents website: https://www.blunham.com/Radar/APlist.html And some pictures of this, with the same double-lines above/below "TREND" can be seen in a few Google images, by searching: https://www.google.com/search?q=Tren...x2CL-Foi8RHmqM So may well be used in something like those (I haven't found any insides-photos yet)