Hi,
some weeks ago i started to repair a ZX 48K. It had no image, sound or whatever.
I Started with a new IC 7805 (tension regulator), and some image appear, but a lot o squares and stripes.
I got some advice, and transistors TR4 and TR5 had to be changed, so i bought ZTX653 (TR4) and
ZRX753 (TR5), desolder the old ones, and solder the new ones, and, howwww, a nice new ZX48k.

Here is a video of the ZX48K, loading a small text that i put in the tape.
http://youtu.be/CPI5BPIT8Jo

Zx is cool, i am now playing around images. i will post a video later of a photo on the screen of the zx.