TV output from original +2

Comments

• Jose_Leandro

  September 2009 edited September 2009

  Hi
  

  MagicKnight wrote: »

  I've modified my 48K Spectrum to output composite, and I have it working here in Japan on my old monitor (X68000). Hopefully my parents will bring over my +2 in a few weeks when they visit. I assume that the +2 outputs composite in the same way and can therefore connect it in the same way. Is this correct?

  
  No. The spectrum +2 ( as same as +128K, +2A,+3) includes a sound carrier. You don't have composite signal en the modulator.
  
  The spectrum +128K and +2 have composite signal in the RGB connector ( not the +2A/+3). The composite signal is in pin number 1.
  
  This web explain very good all this things
  
  http://www.fruitcake.plus.com/index.html
  
  Bye
  
  Jos? Leandro
• MagicKnight

  September 2009 edited September 2009

  Ok, thanks for that. It looks a bit too complicated, given that I don't have a SCART connection on my monitor. It uses a 15-pin RGB input which is common in Japan (FM Towns,
  PC-9801 etc.)
  
  The machine does have an earphone plug so I could use exteral speakers, is that right? It's a long time since I looked at one properly.
  
  Other than that, I don't think I have a chance of connecting it up. Maybe I'll just stick with the 48K model.
• mcleod_ideafix

  September 2009 edited September 2009

  MagicKnight wrote: »

  I assume that the +2 outputs composite in the same way and can therefore connect it in the same way. Is this correct?

  Yes. Although the composite signal carries the FM modulated sound, that shouldn't be a big problem. The worst you can have is some kind of wavering noise on your screen caused by the sound subcarrier. Whether you can see that noise or not depends on how the composite input of your TV is internally arranged.
  
  If this noise happens and bothers you, there's a simple way to eliminate it: locate capacitor C24 in your Spectrum PCB (a very small 33pf capacitor) and remove it. This is the responsible of mixing the video and audio information. If you remove it, you won't be able to hear any sound when using the RF output. The sound output from the 3,5 jack is not altered in any way.
  
  Also, be very carefull when doing the composite mod. I don't know which composite mod version you have used, but you must take into account that the TEA2000 is a very delicate IC, and may be easily destroyed if, for instance, the composite input of your monitor has not the GND connected to the main's ground. If possible, do the composite mod that uses a BC337, a 75 ohm resistor, and a capacitor.
• guesser

  September 2009 edited September 2009

  mcleod_ideafix wrote: »

  Yes. Although the composite signal carries the FM modulated sound, that shouldn't be a big problem. The worst you can have is some kind of wavering noise on your screen caused by the sound subcarrier. Whether you can see that noise or not depends on how the composite input of your TV is internally arranged.
  
  If this noise happens and bothers you, there's a simple way to eliminate it: locate capacitor C24 in your Spectrum PCB (a very small 33pf capacitor) and remove it. This is the responsible of mixing the video and audio information. If you remove it, you won't be able to hear any sound when using the RF output. The sound output from the 3,5 jack is not altered in any way.

  
  funnily enough I was just poking around inside my +3 the other day. a while ago I'd done the composite mod on (building the buffer amp, and hooking it up to the raw output from the tea2000) but it always had noise on the video signal (and elsewhere on the board actually) in the end I tracked it down to the oscillator and FM modulator creating the sound subcarrier that was no longer connected to anything. I've now removed all the sound modulation circuitry entirely as it was just causing trouble.

  My rubbish website including the redrawn Amstrad schematics and the Sinclair Wiki.