Published in 405 Alive Issue 17, dated New Year 1993

FIRST THOUGHTS

I was struck by the simplicity and compactness of the converter. The PCB is only 7" by 5" and is not tightly packed. The whole converter including power supply was in a plastic box 10" by 8" by 2.5". The unit sent for review was a prototype.

The converter is very simple to use. The only connections are mains, 625 video in and 405 video out. The user controls are two switches, one to freeze the picture and a thumbwheel to select interpolation modes. You will need a modulator to run TV receivers. This should not be a problem as designs have been published by David Looser and myself. Pineapple may produce a version with integral modulator.

The construction quality, even on the prototype unit, is excellent. The main PCB is double sided with plated holes. The components are a mixture of conventional and surface mount. Production units should have silk screened component legends too. The mains power supply is on a separate PCB and presents no immediate safety hazard though careless poking around could touch a live connection. A comprehensive manual including circuit diagrams is promised.

The whole converter runs quite cool and so it should be reliable.

INTERPOLATION

Uniquely amongst 405 line converters this design stores a whole frame of video rather than just a few lines. This allows some interesting possibilities for interpolation as well as causing a couple of potential problems. Due to the nature of interlace, successive lines in the video signal are not adjacent on the screen. The gap between each pair of lines from the odd field is occupied by a line from the even field and vice versa.

The Pineapple converter offers a choice of several interpolation modes. One group interpolates lines that are adjacent on the screen. These come from different fields. This is excellent for a stationary picture but causes problems with movement. These adjacent lines are 20mS apart in time. This means that moving objects will be in different positions on the two lines. The visible effect is that moving objects appear with jagged edges. In extreme cases you can see two separate objects. These interpolation modes are not usable except with strictly stationary pictures such as test patterns. Under these conditions they should give optimum vertical resolution though the subjective improvement is small and they made a very flickery job of my crosshatch pattern.

The other group of interpolation modes uses successive pairs of lines from the same field. These are entirely satisfactory for all pictures.

Two other minor points arise from the frame store design. The output is completely asynchronous to the input. As a result an occasional frame may be repeated or dropped. This should only happen occasionally and should not be disturbing. The picture can be delayed by up to 40mS. This is on the verge of visible lip-sync errors.

RADIO INTERFERENCE
The converter contains much high speed digital circuitry which is a potent source of RF interference. If you buy the PCB alone you must house it in a metal box. The plastic cased prototype caused severe interference to VHF radio reception and may interfere with other services such as aircraft and police communications. Pineapple will be using metal cases on production units.

There are also a number of minor engineering compromises in the design which might annoy the BBC but are of no importance to the ordinary user.

PICTURE QUALITY

The subjective picture quality is very good. There is slight overshoot after transitions but this is inevitable when a notch filter is used to get rid of unwanted colour subcarrier from the 625 input. I compared the Pineapple converter with a BBC CO6/509 using a professional video monitor and several receivers both pre- and post-war. The BBC converter uses four line interpolation and is engineered to full broadcast standards. The only readily noticeable difference was that the gain of the Pineapple converter was slightly low. There was also very slight ragging of verticals. I am assured that these problems will be corrected on production units. The unit copes well with VHS replay. The output will always have good continuous 405 syncs even if the input picture is poor or non-existent.

CONCLUSIONS

This unit offers very good performance at an affordable price. Recommended.