Seven Segment Displays

I have a VCR with a mechanical timer -- and it is one of the first domestic VCRs, a Philips N1500. The timer driven by a synchronous motor mains transformer primary winding as an autotransformer). It has an analogue clock face with a coloured band you can move round and adjust in length (up to 1 hour, the longest tapes that were made for this machine). There's another control on the clock that selects whether it will trigger on the first or second time the hour hand gets to the coloured segment (i.e. giving a total range of up to 24 hours in the future). The tuner, though, is electronic. There's a set of interlocked buttons on tope, and the same number of multi-turn presets under a flap. In fact much of the tuner/IF circuitry is the same as in Philips TVs of the period. It's a strange machine. The cassettes have the 2 spools stacked on top of each other, there's a complex dual concentric drive spindle. One result of this is that the head drum is almost -- but not quite -- parallel to the deck surface. That machine is now about 33 years old. In that time it's needed nothing more than a new set of belts, a repair to the threading pulley, and one new transistor in the audio mute circuit. The machine with the 7 segment LEDs is also a Philips -- a VR2022. This is one of the later V2000 machines, taking a flipover cassette with up to 4 hours recording per side. The video heads are mounted on piezo crystals (with a set of brush contacts on top of the head drum), which allows them to be servo-tracked along the video tracks -- a bit like a hard disk head (to get this towards being on-topic ;-)). You can therefore have a noiseless freeze-frame -- one of the problems with other vcr systems is that the apparanet angle of the recorded track to the edge of the tape depends on the tape speed, so if you stop the tape for a freeze-frame, the head wanders off the edges of the track. The V2000 machines apply some amazingly large (over 100V) waveforms to the actuator crystals in this mode, but the heads stay on the video tracks. It's also a machine with very few mechanical parts. The only rubber part is the pinch roller. The capstan, drum, and both reels are directly driven by their own motors (there's a 5th motor for lacing up the tape). There's no back-tension band, back tension is applied by a small current through the rewind motor. Oh, and the electronics is all on plug-in boards, apart from the tuners, RF splitter and modulator, which are soldered to the backplane PCB. There must be about 20 such boards, including half a dozen for the various servos. The service manual (I have it, of course), documents each board sepaarately, and also explains the complete machine. I'd love to find the diagnostic tool for it. This was a box containing a ROM and an address latch with a bit of ribbon cable coming out of it ending in a 40 pin DIL clip. You clipped it over the 8048 on the syscon board and it disabled that chip's intenral ROM and ran the program from the external ROM instead. It would let you do all sorts of useful things. I'd also like to find the baseband I/O adapater. There's a 20 pin non-standard plug on the back that this connects to. It gives composite video and (mono) audio I/O, a remote pause facility, etc. Oh well, enough off-topic rambling... -tony