How to Fix a Sinclair Spectrum +2

December 8th, 2011

After some real trouble with three Spectrum +2s I’ve at least learnt a thing or two (not only about the build quality of those dogs). Most often the problems are caused by failing transistors, with other probable failures on top. Here’s for those who struggle with their Speccy:

  • Power supply busted? They’re still available on eBay and elsewhere too, but any sturdy enough (2A) PSU will probably do. Nominally the voltage should be 9V DC, but you can also feed it a bit higher voltage, because a regulator will turn it into 5V anyway. Personally I’ve used two +2s with a generic 12V transformer. Note that the plug is shield positive.
  • Still no voltage? Check the power connector on the PCB. The solder points don’t seem to last.
  • Power LED doesn’t light up? Time to change the regulator that is attached to the big heat sink. 7805 is the one. Note that they are not all the same: if you intend to use expansions such as divIDE, get one with a high throughput (~2A).
  • Still no picture?
    • There are three ways to get video out: RF, composite and RGB (SCART). RGB is the least fragile of these, so if RF and composite fail, you might at least see something and confirm that the machine is otherwise sane.
    • RGB works, the rest don’t? Most likely TR9 has failed. Replace it with another ZTX650/651.
    • According to some account, it might do some good to change TR8, too. It’s a ZTX213.
  • Distorted composite output? If you can get some dark output from TEA2000 pin 6, things are looking up! Most likely TR4 has failed and needs to be changed. This time you need a 2N3904. The markings on the PCB are upside down: install the transistor the other way around for a bit better image quality.
  • Still no RF output? The RF modulator seems to crack off the PCB by time. The tiny wires bringing the signal in might suffer at that point.
  • Constant noise in the audio output? This is not even a problem per se, but a feature of the +2 design. The tape drive head is connected to the sound output and it picks up all sorts of noise for your enjoyment. If you don’t need the drive, just snap off the white wire coming from it to the PCB. A bit more elegant solution is to place a switch on the wire, which lets you choose between sound quality and a working tape drive.

I hope this blurb is of use for someone. Let me know if there are any additions or errors.

Filed under: laitteet,retro

2 Comments Add your own

  • 1. David Hamblyn  |  June 24th, 2013 at 10:25 pm

    Hi. I am looking for some help. I recently bought a spectrum from ebay but there is a display problem. Rf output displays a blank screen even though an older spectrum plus works on the same channel. I bought the appropriate scart lead but alas the best i can get is a fluctuating rolling picture as if the horizontal hold is gone. Attached is a picture. Please ignore the blue square which is a picture in picture feature on my tv. The computer is working because i can see the menu screen and hear the tapes through the tv speakers. I have been online on world of spectrum and someone suggested a transistor is probably shorted. Could you point me in the right direction? To summarize, rf output is blank but when i retune i can see the menu behind a very fuzzy screen. Scart rgb lead screen is distorted and rolling upwards.
    Thanks
    David Hamblyn
    Wexford, Ireland

  • 2. marq  |  June 25th, 2013 at 8:18 am

    I haven’t seen that particular problem in my otherwise busted +2:s, but changing all the transistors mentioned above would be the first natural choice: they cause most of the problems.

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