The Pineapple standards converter.

[Geordie McBoyne]

The Pineapple was introduced in 1993 and I've heard of no problems with it.
A customer has brought his Pineapple in for repair.  The fault is poor synchronising on certain types of picture content.  Although I assembled one for my own use I've never explored the electronics. Now's the opportunity to do so.
 I was about to sign off the repair of the one which is the subject of this discussion but yesterday when it's owner called in to collect the converter that old problem manifested itself again.  The problem we're experiencing is black level shifts and sync pulse crushing.
For test purposes the converter is supplied with video from a DVD player, the fault is not apparent on a test pattern.
My attention was first drawn to IC U14, a 74HC4066 quad bi-directional switch. First check the black level clamp, pins 6,8 and 9. The 9uS clamp pulse is present at pin6, adjustable DC reference present at pin 9. Video sans syncs present at pin 8. Inverted mixed blanking present at pin 13. Mixed syncs present at pin 12. Fixed sync tip reference present a pin10.
A good test point to monitor the composite video is at the emitter of Q8, the video signal is correct. Move on to the final amplifier stages which consist of transistors Q9, Q10 and Q11. The fault is apparent at the emitter of Q11 and the load resistor R49.
It seems that the input stage of the modulator is causing the fault, black level shifts when the picture content changes and also sync crushing.
So now my attention when be on the RF modulator module.

Geordie McBoyne.

[Ed_Dinning]

Hi David, I'm not sure if you have totally eliminated the 4066, but these chips are notorious for being sensitive to static. I've got plenty of them here if you need some.

Ed

[Geordie McBoyne]

Hi Ed,
I've eliminated any problems with U14, the 4066. I can fully understand why the designer chose the chip, the functions of black level clamp, blanking and sync adder all performed by a single IC. Its an unusual choice of component for the task, you normally find transistors employed to perform these functions.
Referencing to the Black book, the design concept has not changed since the thirties. The output from the camera is amplified then DC restored with black level set to the required voltage level. The next stage is the mixed blanking which is adjusted to same voltage as the black level Finally, the mixed syncs insertion, which is essentially a gated level shift arrangement.

Geordie McBoyne.

[ppppenguin]

I reviewed the Pineapple converter for "405 Alive" when it first appeared in 1993:
http://www.borinsky.plus.com/pineapple_4...SSUE17.PDF

An interesting design as it used twin DACs and an analogue interpolator.

I agree with Ed that the 4000 series analogue switches (4016, 4051, 4052, 4053, 4066) and their HC/HCT equivalents can be prone to failure, probably due to static. Failure isn't always immediately apparent.

I'd be tempted to do a bulk change of the electrolytics. A minor failure in C41, 42, 43 could cause all sorts of havoc.

[Murphyv310]

Hi.
The pineapple was my first 405 line standards converter, I had it for a couple of years and built it into an Akai VCR that had no mech. Although I was happy with it at the time the Aurora Multistandards converter that came along later was far superior. For ease of use and quality the Aurora SCRF Converters are undoubtedly the best.

[ppppenguin]

Summarising the 405 converters that have been marketed over the years, hence not including David Boynes, Kat Manton etc.

In roughly chronological order:

Dinosaur: Well engineered unit. I'd still be happy to use one if I had one
Pineapple: Not as well engineered as the Dino. Generates a lot of RFI unless you're very careful with case and connections. Don't think I'd use one now
Domino: Slightly limited bandwidth so pictures will look a little soft on a really good set. Otherwise good. Included a Ch1 modulator which made it very easy to use.

First Aurora. A rare beast, multistandard without a modulator. Brilliant design but lack of modulator made it harder to use.
Aurora SCRF. Still the definitive 405 converter. First with multichannel modulator More sold than all the others put together. Probably over 700.
Aurora WC-01. The luxury converter capable of all known standards including modulator. Not many sold, mainly due to high price.

[Geordie McBoyne]

It is in fact the modulator that is causing all the problems. The modulator is the type that was made by W. Meier in I believe Germany.
I have no circuit information for this unit. Visible from the top side of the PCB there is a 45Mhz crystal controlled oscillator which employs a BF245 FET.
A 78M05 5 volt regulator IC. A few capacitors and resistors, two coils, one I assume is the 41.5Mhz oscillator for the sound carrier.
On the print side of the PCB is a single surface mounted IC of an unknown type, it is this device which is suspect.
The modulator is contained in a 70 X 70 X 30mm metal box.

Geordie McBoyne.

[ppppenguin]

Photo would be useful to help us identify what's going on. Doesn't sound like the classic Dave Looser or JB type of design which use 2x 1496 balanced modulator chips. One each for sound and vision. I wonder if it could be close to Darius's circuit which I've attached.

[Geordie McBoyne]

Pictures of the modulator.    

Geordie McBoyne.

[ppppenguin]

Not a lot there! Any marking at all on the chip? Hardly looks enough for a vision modulator, let alone sound.

A not very useful reference here: http://www.bvws.org.uk/405alive/tech/modulator.html