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Determining +3 revision

brownb2brownb2
edited April 2010 in Hardware
I have two +3's and have only just got around to inspecting the insides to look for the known +3 sound "bug".

The problem is that one machine appears to have a louder default sound output via the RF lead that seems to be distorted due to the volume. Both machines to my knowledge have not been modded.

Both +3's have a main board with "Revision 2" (IIRC) near the Amstrad name, which I took to be that they were +3Bs. Is this correct?
Post edited by brownb2 on

Comments

  • ZupZup
    edited March 2010
    Fast method... locate TR5 and measure resistance between GND and the upper terminal in TR5 (upper=nearer to RF modulator). In bugged +3 is 0 ohm (that's the bug).

    Also, I think that TR5 doesn't exists in +2A nor unbugged +3... in my schematics it has been renamed to TR200).
    I was there, too
    An' you know what they said?
    Well, some of it was true!
  • brownb2brownb2
    edited March 2010
    Zup wrote: »
    Fast method... locate TR5 and measure resistance between GND and the upper terminal in TR5 (upper=nearer to RF modulator). In bugged +3 is 0 ohm (that's the bug).

    Also, I think that TR5 doesn't exists in +2A nor unbugged +3... in my schematics it has been renamed to TR200).

    Is there a non electrical method? I've just been looking to see if I have the bug and whether I need to invest in a multimeter and soldering iron :)
  • ZupZup
    edited March 2010
    Zup wrote: »
    Also, I think that TR5 doesn't exists in +2A nor unbugged +3... in my schematics it has been renamed to TR200).

    I've never seen a "newer" +3 release, so I don't know if that sentence is really true... but you may give it a try. Another method would be following the track to visually check if TR5 is connected to a 220 ohm resistor (red-red-brown).

    Other method would be using a PC to check +3 sound output.
    - First, find a program that generates a sine wave through AY.
    - Load it into the known good speccy and capture the output (ten seconds or so will be enough) with the PC. Check the recording volume so it doesn't go above 50% (to leave "space" in case +3 is not buggy, only loud). In a wave editor (audacity), your sound must appear as a sine wave. Select only fractions of second, in other case you won't see the waveform clearly.
    - Repeat the process with the other speccy, without touching any volume control. If the wave is not a sine one, but a clipped one... congratulations, you have a first revision +3 ;)
    I was there, too
    An' you know what they said?
    Well, some of it was true!
  • kpuchatekkpuchatek
    edited March 2010
    To my notes, there were three revisions of +3:
    +3 Issue 1 Z70830
    +3 Issue 2 Z70830
    +3B Z70835 ISSUE 1 (c)1988
    See:
    http://tomdalby.com/retro/hardware.html

    +3B I have never seen, but seems to exist in service manual.
    Anybody to have one ?

    I'm think only +3 Issue 1 has distorted sound and it is not related to presence of resistor in emitter output.
    Analog circuit master to comment :-)
  • brownb2brownb2
    edited March 2010
    kpuchatek wrote: »
    To my notes, there were three revisions of +3:
    +3 Issue 1 Z70830
    +3 Issue 2 Z70830
    +3B Issue 1 (don't have now number, but will find)

    +3B I have never seen, but seems to exist in service manual.
    Anybody to have one ?

    I'm think only +3 Issue 1 has distorted sound

    It would be useful if those people who fixed the +3 sound problem could confirm which version of the mainboard they had?
  • Dave FountainDave Fountain
    edited March 2010
    This may be a ridiculous question, but why did Amstrad release a machine into the marketplace that had very poor sound quality? Did all +3 models suffer from it? Was it fixed, Was it even admitted to? I've always found this topic about the +3s sound deeply disturbing. I'd like to read the definitive answer.
  • Alien 8Alien 8
    edited March 2010
    Dave Fountain wrote: »
    This may be a ridiculous question, but why did Amstrad release a machine into the marketplace that had very poor sound quality? Did all +3 models suffer from it? Was it fixed, Was it even admitted to? I've always found this topic about the +3s sound deeply disturbing. I'd like to read the definitive answer.

    I got my +3 for Christmas 1987, so it must have been a very early example. It was in the Currys Live Ammo bundle. It always sounded like it was underwater, and because the sound came through the TV speakers it shared the problem that I had with my VIC 20, that is get the picture right and the sound buzzes, get the sound clear, and the picture isn't too good. Our TV didn't have SCART back then.

    I recently got the AY magic sound module. I played Tetris and heard the same music that I used to hear when I played Tetris on my +3, but beautifully clear, and in Stereo. This is what el cheapo Amstrad should have done back then, but then I suppose it was an improvement on a beeper...
  • wootlanterwootlanter
    edited April 2010
    Sorry for my ignorance, but this bug means the sound is distorted, right?

    I never use the RF output on my +3 (infact, I broke it by trying to adjust that trim pot that's on it!). So I use the din to scart. The sound is actually quite distorted. But I don't remember it being quite so distorted when I used to use the RF output...
  • ZupZup
    edited April 2010
    That's probably because the crappy modulation system used. The sound and the video carrier seems not adjusted, so you must choose: good video and interferences in sound, or interferences in video and good sound.

    So maybe you won't notice the distortion because you were hearing white noise.
    I was there, too
    An' you know what they said?
    Well, some of it was true!
  • wootlanterwootlanter
    edited April 2010
    I see.
  • SwainySwainy
    edited April 2010
    wootlanter wrote: »
    I see.

    It's strange how the +2 was never affected by this sound bug. Didn't Amstrad use the same parts for the +2?
  • guesserguesser
    edited April 2010
    Swainy wrote: »
    It's strange how the +2 was never affected by this sound bug. Didn't Amstrad use the same parts for the +2?

    do you mean the +2A?

    the +2 is nothing like the +3 except for the shape of the case.
    My rubbish website including the redrawn Amstrad schematics and the Sinclair Wiki.
  • SwainySwainy
    edited April 2010
    guesser wrote: »
    do you mean the +2A?

    the +2 is nothing like the +3 except for the shape of the case.

    Yeah, sorry I meant the +2A. I'm guess that the later +3's were released at the same time as the +2A?
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