Hacking a +2 into a shorter case

If anyone's got a copy of the notes or text they posted about re-wiring the +2 joystick ports or hooking up a tape recorder to the motherboard cassette header, please can you re-post it here?
Joefish
- IONIAN-GAMES.com -

Comments

  • edited May 2015
    joefish said:


    I'm putting together one of those shortened +2s. What I want to know is, can I put the keyboard membrane from a Grey +2 inside the keyboard module from a Black +2A/+3, as I want black keys on it?

    Interesting that the grey membrane has two layers and similar 8+5 ribbon connectors as a 48K (though off to the side, not the top), but the +2A/+3 has more lines in the membrane. Yet I've seen someone put the 8+5 ribbons in the top of the wider slot on a Black +2A and it works. But I bet the extra lines on the black membrane aren't redundant - are they to get round the dual-layer problem of having to operate shifted keys? Are the extra lines re-connected to the original 8+5 somewhere on the circuit board?

    And does anyone sell spare +2 / +2A / +3 membranes?

    Also, is it possible to wire Ear / Mic sockets from the cassette recorder connector? Is the headphone socket analogous to one of these, and can you use that for saving and loading?

    Finally, has anyone got a handy guide for re-wiring the joystick ports, or do I need to just look up the mappings myself and work it out?
    balford said:


    Yep, membrane from a grey +2 will work fine. Not sure about the fitment of the metal backplate, but worst case scenario you can replace the grey keytops with black ones.

    The extra lines in the +3 membrane are there so that the four layer membrane construction of the earlier machines can be done away with, and the remapping back to 8x5 is done internally within the +3 ASIC.

    Tradeinpost.com do +2A/+3 membranes but not +2, don't think there's a source for those.

    EAR/MIC sockets are tricky, not done it myself but I hear good things about connecting directly to the playback head pads on the tape PCB, obviously you'd have to retain that somewhere within the shortened case.

    I've done the joystick rewiring, unfortunately the guide for doing that is on WoS and I don't have it archived anywhere. If you can find the Spectrum side pinouts it's straightforward enough to work out.

    B
    bugpat said:


    Hi,
    I did all that on my "+4", and the infos are on WOS, but... not for the moment !

    So, you can put the grey membrane in the black +2A keyboard, it will fit perfectly.
    If you use the Ear / Mic sockets from the cassette recorder connector, you'll have to use an amplifier to load something (if you want to use a small mp3 reader for example), because you won't have the original tape recorder amplifier, that's why I tried to use the head pads as an audio-in on my "+4" , and this is OK, I can load games from my iPod, iPhone...
    And I rewired the joysticks ports on all my +2 / +2A / +3, and you're lucky, I still have those pictures on my computer, here at work :) :

    Solder side view :

    image


    Modification on my +3 :

    image


    And the result on my "+4" :

    image


    You can plug your soldering iron now :D
    joefish said:


    Surely it's the same as the EAR/MIC sockets on a regular Sepccy? They don't have an amplifier either. If I'm using an actual tape recorder, can't I load and save normally?

    The +3 seems to have a combined EAR/MIC socket using a stereo connector. What does the +2 have, and is it the copy of the EAR or MIC socket? And what are each of the tape connector pins?
    1024MAK said:


    All +2 machines have a "stereo" socket but with only a single mono audio out on one of the signal connections (the tip on "stereo" 3.5mm jack plugs) [at least! that is the official line]. However, on most boards both of the signal connections (the tip and the sleeve) are connected together giving two mono channels on a "stereo" jack socket.

    It is the equivalent to the Mic socket ( where Mic refers to the relevant socket on a mono cassette deck that the lead is plugged into).

    An unmodified +2 has no input so cannot load from an external tape player.

    Mark
    joefish said:


    That's what I thought it's the same as the MIC, which is actually output.

    But what's this about needing to leave the amplifier in the tape connector header? Isn't one of the pins on that header simply the same as the EAR socket on an old Spectrum? Ad if so, which one can I divert to an ear socket of my own?


    On a +2 the external audio is nerfed - you need to disrupt the track going across the Ear connector and connect it to the tape cable header - it should be easy to work out which pins on the motherboard (to datacorder) should go to the ear. Use the absolute minimum length of wire and make it as neat as humanly possible to avoid noise issues. Personally, I just hotwired an old jack cable to the datacorder connection, then it works great using an MP3 player or laptop and the built-in ear connection is left just for audio output, which I don't even have a need for.

    On my C64 I just taped on an old azimuth tape adaptor thing - it's not the prettiest option but it's the least disruptive and would do the job if your worried about having to solder.

    I got an MP3 player and a set of Cherry MX switches and replaced the datacorder, so it's a little screen and microswitched buttons to select games - should be wonderful, but the MP3 player is half dead and it's tricky to find one that has wired buttons, a screen, and is a sensible size for the datacorder tape 'window'. I wish someone would make a little MP3 player tape that has an actual screen.
    joefish said:


    Thanks for that. That's what I meant - to add my own jack socket. So just wiring a new socket to two pins of the header works for input from an external tape deck?


    Yeah, that's what I did and haven't had any problems with it.


    which section of wos?
    the documentation is here
    http://www.worldofspectrum.org/documentation.html#manuals
    seems to be working??
    joefish said:


    I've always found it hard to get a straight answer to written questions from that section of WoS compared to, for example, the forums... ::)

    EDIT - Actually, all those links demand an ftp password, anyway.
    1024MAK said:
    1024MAK said:


    Here is a zip file with details of how to add a tape in (ear) socket to a +2A / +2B

    Edit: hmm, that did not work. I'll convert it...

    Edit2: Okay, here it is as a PDF version ;) Ear and MIC connectors for the 2A PDF versi....zip (178.23 KB)
    EDIT3: Sorry, no attachments available on WoSF :(
    I can email this to anyone who wants it though.

    Mark
    joefish said:


    Hate to put off anyone trying to help, but it's not one of those. Only the original +2 has the short motherboard that will fit in a custom chopped case. And I suspect the pins in the tape header connector are different. But thanks, I'll take a look.
    1024MAK said:


    Yes, but until WoS forums are back up, it gives you some ideas ;)

    I'll dig through my archived files and see if I actually have anything relating to the grey +2 (but don't get your hopes up, at the time I did not have a grey +2 so may not have saved anything).

    Actually, thinking about it, I have a good schematic of a +128 toastrack and the +2 grey uses the same ULA...

    Hang about...

    Mark
    joefish said:


    Yep, I was thinking if the board isn't labelled one could trace the lines from the ULA. Though that might be tricky without a maintenance schematic...

    Funny, i assumed this was something that had been done over and over again.
    1024MAK said:


    Which +2 grey version board do you have?

    On one of mine, a board with "0500 ISS3" silk screen printed on the component side and marked "Z70500" on the bottom side:-

    1, Connect a 1N4148 diode across R82 (front left of PCB just to the left of the "0500 ISS3" text) with the stripe on the diode on right hand side. That is anode on the left and cathode on the right.

    2, Connect a 100nF ceramic capacitor to the tip / centre contact of a 3.5mm mono jack socket.

    3, Take a wire from the cassette plug (PL12) pin 4 and connect to the other leg of the 100nF ceramic capacitor on your 3.5mm mono jack socket.

    4, Connect a ground wire from the other 3.5mm mono jack socket contact and one of the ground (GND) connections on the cassette plug (PL12).


    image
    image
    image

    Note the wire colours used on the cassette deck to the main board may not be the same in all machines.

    Mark
    1024MAK said:


    This is the toastrack version of the circuit, but I'm not sure there should be a direct connection between ULA pins 34 and 35! I think this is a drawing error.
    image

    1N4148 diode picture

    Mark

    All the above quotes were taken from the World Of Spectrum (Temporary) Forum

    Sorry about the double line spacing. With this new forum edit box, it is hard to get text looking good, as the edit box display is inconsistent  with the final result :(
    A gazillion edits later...

    Mark

    Post edited by 1024MAK on
  • Ah - a masterpiece of thread recovery. Even the pictures work. Ta chap.
    Joefish
    - IONIAN-GAMES.com -
  • Yes thanks Mark and Joe ,very useful : very good info : Worth a go definitely
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