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380Z

Gary C

Gary C

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Joined
May 26, 2018
Messages
2,818
Location
North Yorkshire, UK
Picked up a 380z a couple of years ago with the keyboard but this week I have managed to have a look at it. I wanted one of these as soon as I got into collecting.

All the cards found lying haphazard and out of their card frames, with the guides loose. The guides are a little deformed at the bottom and look as if they have been overtightened at some point. Could do with an insert to make them more rigid at the bottom. Might be a thing for a 3D print in the near future.

First off, a strip down of the case and to whip the PSU out for testing and it looks pristine. Works perfectly.

The case has had a few dings and the disk drive mount is bent. The feet are badly damaged but not sure what type they were, did the RML have the 19" instrument case type with extending legs or were they simple affairs. Can't find a picture of the underside of one to compare.

With the PSU out, coupled up the CPU and video card for a test as in the case they are impossible to access when installed, and... it works. video showing COP 4.3 ! Yay. I think I have a hires video card somewhere in the garage, so time for a hunt.

Next I need to give both drives a thorough overhaul before I try one of the disks in it.
 
Must be one of the hardest machines to test.
The keyboard isnt working so its a total nightmare getting the cpu and video card out of the chassis and setup for testing, but I think I have almost managed it
1000008722.jpg
Need to make an extension for the 'keyboard' connector though as its also wired into the cassette port connector which is riveted into the rear panel :(
 
Keyboard extension installed and now I can see the microcontroller is running

1777399534615.png

But I can't workout the physical keyboard. IC4 is strobing each output line and each of these lines goto a pad on the underside of the keyboard
ie from pin 2 of IC 4 it goes to these two pads
1777399534650.jpeg
Now on the otherside are two matching pads, with half moon pads that in this case, connects to resistor R11 and pin 15 of IC9
1777399629191.jpeg
Now, the foil pads of the keys, bridge these pads and thus I would expect they should connect pin 2/IC4 to pin 15/IC9 when this particular key is pressed. However, there is no connection between the pads on the bottom of the PCB and the matching pad on the top of the PCB. It looks as if there is a via between them, but there seems to be physically nothing there !
Now before I start bridging them to test, can anyone cast light on it or work out what the circuit with all the transistors and inductors is for that ultimately connects to input pin 39 of the microcontroller ? Its not meant to be capacitive by any chance ?

The foils on the keys look perfectly good, but have no measurable conduction.
 
So long tailed pair and when the key pressed is selected, the rapid strobe of that line is fed into the diff amp which due to the inductor, produces a pulse, fair enough.

But not having the pad on the bottom connected to the pad on the top that is actually touched by the foam capacitive pad, just doesn't seem right. I must be missing something. Capacitive connection through the PCB ?
 
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Ah , so it sounds as if the top and bottom pads are the capacitive unit, and the foil should be conductive ? (Which they aint).
 
So, the top and bottom pads use the PCB as a dielectric and the pads are capacitive too. Transistor array changed and screen now responding to button pushes, but not with the right characters.
 
Fault seems to be with the latching of the data to pass to the machine. Pretty sure that the 8 data lines from/to the MPU are ok as it is running the program from the EPROM ok, so surely the latch.

Oddly though, the device fitted is a 74LS377 and not the 74LS374 shown in the drawing. They only differ in that the 374 outputs go high Z when enable is high, whereas the 377 holds the data on the outputs. Looking at the VDU80 card where the keyboard connects, its not onto a bus, but into another 74LS374 which suggests I would be better using a 377. Got both on order anyway to try but scoping it out, only two outputs on the installed device are actually changing so its looking rather dead. It also has that black silver corrosion and at least one leg has a full width crack.



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While I wait, had a poke around the workshop and turned up a Hires graphics card for this 380Z, knew I had it somewhere.

Looking at the VDU80 card schematic, it looks as if the HRG can pass video to a 14 way DIL socket and mix it with the text video on the card. Signals go from VDU card to the HRG to sync it, then video from the HRG goes back to the VDU card where its mixed and sent out through the normal route (phew)

However, I dont have the cable and therefore need to find the right video connector which looks like this, and its small. SMA small, but doesn't screw in and the centre pin appears fatter.

1778320593251.png

Cant find one, google image search fails so any ideas people ?
 
74LS377 changed for a 74LS374 (as per drawing, but realised that, with pin 1 tied to 0V they are functionally identical) and the keyboard has leapt into some sort of life. Top row of number keys work perfectly, but those on lower rows give the wrong codes.
Put the Logic Analyser onto the new 374 and that's working fine so checked the IC at the other end of the connector on the VDU card, and replaced the 74LS374 at position CV and now it works (I am assuming it starts up in lower case).

Next job is to rebuild the keyboard and fit the CPU and VDU card back into the main chassis and test the floppy disk interface & drives but its getting nearer :)

Still cant find the video connector though.
 
Gary, this is all I know that looks remotely like your connector. It was old when I got it in 1964, and I think we called them Post Office Connectors (as in Dollis Hill, London). It has what looks like a NATO number on it: 5935-99-011-9811. The outer (ground) connection is about 1/4 O/D. The nearer knurled thing is threaded and does screw on to a male chassis connector.
L1010526_b.jpg
David
 
interesting, thank you.

The barrel on the plug is 0.175" in diameter so significantly bigger than a SMB.

I have looked up this connector now but cant find that NATO number 😞
 
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The barrel I mean the bit at the front with the split in it and the contact inside it. The RML connector is 0.175" or 4.45mm

SMB is a connector that looks the same but is smaller at 3.6mm
1778824890338.png
 
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Thanks to Qbertnix, connector identified (fingers crossed) as a Belling Lee 1465B/FP.

And just managed to locate some on ebay (miss identified but they look right)

Hopefully I can make up a interboard link that looks like the original.
 
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