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Discussion in 'Offtopic Discussions' started by T.T., May 20, 2014.

  1. Cerbera

    Cerbera Ecnes

    Jun 16, 2007
    I've attached v0.000000000000000000000000000000001 of The Journey Home to this post for people to try out if they wish.

    How to play: Extract the archive then double click on the HTML file.

    How to modify: Either use Twine's import file feature or edit the HTML file directly using your favourite text editor.

    License: CC BY-NC-SA 4.0

    Attached Files:

  2. PCXT

    PCXT Very Active Member

    Sep 14, 2016
    More from Galaksija "replica" log:
    (first part: Here).

    Initial assembly started. Lots and lots of jumper wires, I haven't soldered them all. Going from right to left, jumper wires first, then IC sockets. After I soldered copper wire as jumpers in ZX97Lite clone and it darkened, I decided to use insulated wire with nice green insulation where possible. So, under sockets it's impossible, and under keys too, copper wires from network cable go there.
    These nice Tesla green sockets won't fit as it's not too much space between ROM/RAM sockets. I used one in character ROM.
    There are more problems than I initially thought. I see that tracks are porous, it's hard to stick solder to them and if it sticks, it sticks to the PCB too. Soldered ROM/RAM sockets, it's hard. The only method to finally stick the socket's pin to track was to install socket, bend pins outwards or inwards as much as possible, brush it with flux and use capillary forces to pull the solder: Heat the pin, push the alloy under it.
    Some tracks have visible holes, some have visible links. Before starting it will be needed to clean the situation with an ohmmeter, soldering iron and knife. Tomorrow: CPU region.

    Assembled keys, sockets, jumpers and most resistors and capacitors. There are significant problems with tracks, lots of fixing as they are "porous", so ordinary coating with alloy does not fix the problem. The keys used are a bit different than original, so I had to modify holes and it's impossible to correct their orientation as it was with original computer using a separate plate. It generally looks nicer now, no shorts on RAM/EPROMs, character ROM not tested.

    Assembled everything. Removed more shorted/opened tracks. Startup -> No clock. Removed problem with too big cap in generator circuit, restored broken connection between inverters, clock ran, there even is something like a sync, but nothing more. Found that D0 is shorted with clock and corrected it. Still no result.
    No reaction to reset. There are errors on official schematic, especially related to pin numbers on glue logic. Russian schematic (Fifan's) is better, the only mistake seems to be related to data lines on 74LS174 in which two of them are flipped, but on the other side of chip they are flipped too. Additionally something seems to be wrong with resistors for video, so I'll take video from between resistors of a modulator divider. It looks like the machine bursts all components on the same logic levels, so everything goes messy.

    OK, there are probably more bad connections, let's roll heavy cannons now. No boot up and CPU does some babbling on buses, activating RAMs and EPROMs. I decided to buzz through all connections using Russian schematic as a reference. Found that two chips just have no power and quite important connection to move video out is broken. Fixed and tried to boot.
    Partial success - there is a READY prompt, but the computer seems not to work stable way - CPU hangs, memory writes are going not where intended, and picture lines are missing, LISTing simple program returns gibberish. Because the clock is derived from a single oscillator, I decided to diagnose the following way:
    1. Change CPU. This computer seems to work well with a "80A MME" East German CPU... and no other. Even original Zilog's Z80 and clone with "R" in logo break timings and it crashes before displaying second picture line (ROMs stop to be readable too early).
    2. Mess with capacitors. This was a good idea. I had no other 5nF, so hacked 4n7 using soldering iron :). CPU seems to run stable now, but picture is still missing random lines and... it looks like it warms up, after 20-30 seconds it's OK.
    3. Mess with generator. Good that I have an oscilloscope.
    Now the most important thing to fix this issue: Without oscilloscope, Initiating this computer is just trial and error. Timings are critical, one gate flips too fast (still in datasheet tolerances) and data goes to the wrong place. I have bought a new inverter chip for clock generator as I knew that this is a generator, parasitic capacitances in dirty connections from unsoldered 30 year old chip may kick in, gates have to be fast, don't they? Well, here NOT. The clock for pixel generation just has to be delayed specific amount of time or it will make italics. I finally found a set of logic that works with minimum capacitors added and there is this 30 year old 74LS04. Additionally, my new CD4040 (manufactured 2010) used as clock divider seems to mess timings too (firing interrupts too fast) and I had to use an old Harris chip to make it go properly.
    The computer successfully executed a simple arithmetic program for 15 minutes and did not hang! Draws about 0.66A of 5V, so it can be fed using 78L05 regulator.
    Summing up: Now I have to find a cheap casing for it.
    I got the mainboard laminate from my friend who was working in laminate factory years ago, I also have A4 samples of other laminates, not copper-coated. Maybe I'll make a frame of flat wooden boards, in which the front panel made of laminate sits on junctions in angles, and the mainboard just slides in? Something like this.
    FBnil likes this.
  3. T.T.

    T.T. Master of Lightning

    Oct 8, 2010
    Somewhere between the Sun and Pluto
    This is a programmable sound generator implemented using TTL chips, and using an arduino for sending commands
    The goal is to have 3 pulse channels, 2 triangle channels, and 2 noise channels.

    This is a single pulse channel. It can do MIDI notes 57-127, has 16 volume levels, and 12.5% 25% and 50% duty cycle options. (it's basically the same as the NES pulse channels)

    Here's a video demonstrating the variable duty cycle. The audio is very quiet.
  4. pmprog

    pmprog Advanced Member

    Apr 25, 2011
    I never finish any projects, but I some times look back and am quite impressed with how far some of them got... Maybe I should pick one an try and polish it.

    Here's the last build of Turn Fighter.
    klapse, FBnil and ible like this.
  5. PCXT

    PCXT Very Active Member

    Sep 14, 2016
    So here is the final version of my Galaksija replica:
    (complete build log with photos)

    Some time ago I assembled it completely and made casing of wood, made a few programs and tested existing ones.

    And here's the most important thing I learned from building:
    Adding blue dye to white paint causes it to become blue only to some degree. Adding more dye then will NOT darken the colour, even if the dye itself is darker.
    Yes, this was supposed to be dark blue.
    And about this poor laminate I mentioned earlier. FR-4 states for "Flame Retardant", and usually is made of glass fiber and epoxy resin, so sometimes it's translated as "Fiber/Resin". This particular factory labeled this laminate as "FR4" because it was "Fenol Resin". For filler, probably paper was used.
    ClockworkCoder, mati, klapse and 3 others like this.
  6. levi

    levi Still fresh, damnit!

    Oct 6, 2008
    Somewhere off the coast of the EU
    Yeah, phenolics and paper is the old pcb tech. Probably old stock they were getting rid of.
  7. directive0

    directive0 Very Active Member

    Apr 8, 2015
    Toronto, Canada
    Got a new video in the pipe on the topic of my PowerMac 7100. Doing some rendering on it just for fun.

    Attached Files:

    levi likes this.

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