Like a buss I wanted a Spectrum and ended up with 3

[Ast A. Moore]

Do Spectrums still run at 50Hz in the US then? I know there were a few different models over there, including the Timex and the NTSC Spectrum.

The NTSC Spectrum used a different ULA and different crystal oscillators with frequencies that could be divided into the multiples needed to comply with the NTSC TV standard. Aside from the US Timex machine, there were no Spectrums made for the United States. The actual NTCS Spectrum was intended for other NTCS countries like Chile, Cuba, etc.

As for the Spectrum itself, it could run from a 9V battery, for all it cares. It needs DC voltage to run, not AC.

[1024MAK]

As said above, the power requirements of the ZX Spectrum 16K through to the +2 (grey) are not special.

Any smoothed or regulated DC PSU at a nominal 9V rated at 2A (or more) and with the correct polarity will do.

Of course, as explained above also, a regulated DC supply with an output voltage in the range 7.5V to 9V is preferred, as it allows the 7805 voltage regulator and its heatsink to run cooler.

The original Sinclair ZX PSU can still be used if you wish. You can also replace the 7805 voltage regulator and its heatsink with a modern DC/DC converter (for example, a RECOM, or other similar device).

The ZX Spectrum 16K through to the +2 (grey) will even run off a battery.

The most important things are:

• Buy new PSUs from trusted retailers, trusted sellers or known brands that are sold in your own country. Stay away from cheap rubbish from overseas. This is because there are bucket loads of cheap and nasty PSUs available from overseas where mains voltage safety has been compromised to keep the price low.
• Always double check the polarity before plugging it in. Get this wrong and it will destroy your ZX Spectrum. Better still, get an inexpensive multimeter and test before connecting the PSU to your Spectrum.

Mark

[1024MAK]

Absolutely no ZX Spectrum models (and for that matter, any Timex Sinclair models) need any 50Hz or 60Hz signals on their power inputs.

All timing signals used in these computers are derived from one or two crystals. As said above, different frequency crystals and different ULA/gate array chips are used depending on the TV standard in the country where they were intended for use.

With modern multi standard TVs, it is sometimes possible to run imported computers with different TV standards in your area.

And there are some people in 120V 60Hz land that use U.K. model ZX Spectrums.

Oh, and one last thing, the AC component (known as ripple) on the output of a U.K. original Sinclair PSU used in the U.K. on a 230V (240V) 50Hz mains supply will be at a frequency of 100Hz, not 50Hz... [This is due to a full wave bridge rectifier being used].

Mark