The Pineapple standards converter.

[Geordie McBoyne]

Hi Jeffrey,
there is no markings on the IC, or any hint to what it might be. It's too small to be an MC1374. Sound is present so there must be some sort of modulator present on the board.

Geordie McBoyne.

[`FRANK.C]

Hi Geordie
I can see 14 pads for a DIP IC. If there was a DIP version of this chip that went obsolete and the SMD version was then used. The SMD version may have been mounted upside down, with the markings on it to the board so that the pins line up with the DIP version.
It wouldn't be the easiest thing to remove with out doing damage.

Was there ever any chip to do both AM sound and vision?

Frank

[ppppenguin]

The Freescale MC44BS373 chip in the Aurora, also used by David Robinson and others, can do AM sound but not with 3.5MHz spacing from vision. Presumably a French modulator would have needed a chip that did AM sound and the Freescale chip can do that. There may well have been others.

The common MC1374 is, I believe, FM sound only.

http://www.nxp.com/files/app_specific_st...4CC373.pdf

In theory the sound could be modulated on to a 3.5MHz subcarrier which is added to the vision ahead of the vision modulator. AKA intercarrier sound. The problems that afflict intercarrier demodulation are mainly absent, the only real requirement is for good linearity in the vision modulator to prevent sound/vision intermodulation. I wonder if the Meier design uses this approach. It would explain the lack of a 41.5MHz xtal. This method could be used with any vision modulator, chip or discrete, possibly including the MC1374 provided its sound modulator can be disabled.

[Geordie McBoyne]

Hi Frank, Hi Jeffrey,
                             many thanks for you input about the modulator problems.
Some good news about the Pineapple converter.  The video amplifier part is supplied from an 8volt source, or it should be.   The two resistors associated with the LM317 regulator had changed in value, thus reducing the supply to just under 7 volts.  Also, there was a 15ohm series resistor between the 20 volt supply and the input pin of the regulator.  I've reduced it to 10ohms.   So now we have exactly 8 volts for the video amplifiers and what a difference that has made. No more sync crushing.  For test purposes the modulator part of the Aurora is being used to supply 405 line signals to the TV receiver. 

The modulator chip is indeed a fourteen pin device.  For some reason or other the chip is buried in some sort of wax compound.

Geordie McBoyne.

[`FRANK.C]

Hi Jeffrey
So then it could be any 14 pin AM modulator chip.

Hi Geordie
That's good progress. In the photo the print can be seen from the component side but I cant see any tracks going to the SMD chip underneath. Maybe the chip is wired in to the DIP pads the wax holding everything together.  Would the wax have gone conductive?

Frank

[Geordie McBoyne]

Hi Frank,
             I've melted away the wax and now we know why it was applied in the first place.  The wax was used to protect the very thin connection wires used to connect an SMD type device to a PCB designed to employ a standard 14 pin N type IC package. That is an IC with 0.1inch pin spacing.
It's assumed that the IC is faulty so I've nothing to loose by removing it in order to find out the type it is.
The attachment shows clearly that it is an SMD chip. So it's possible when it is removed and identified there might possibly be a pin for pin compatible device available to replace it.

Geordie McBoyne.

[Murphyv310]

By gum that looks a rough job!!!
Far too much solder on those joints. I'd say it would be an easy removal, no signs of adhesive in the chip's body.
I sincerely hope you've taken a decent deposit on the repair and charge appropriately. The demise of CHS is a reminder that we are a dead trade now and we should realise if this is our only source of income that a job like this should be worth our while.

I'm surprised that no number is printed on the top surface of the chip, I wonder if the number has been erased from the top of the component, if so again why this trade is good at knocking us for six

[Geordie McBoyne]

Hi Trevor,
             It sure is a rough job.  The SMD type chip is mounted on the print side of the PCB with it's topside to the surface of the board. With luck we'll be able to identify it, assuming that the print has not been rubbed off.
The demise of Charles Hyde and Son (CHS) just tells us about the trade, it's finished and has been for many years!  The company has been in business for fifty years.  CHS will pass on their customers to ASWO.

Geordie McBoyne.

[`FRANK.C]

It would have easier/better to have mounted that chip top side. Just extend the legs as they have done and use the holes drilled for the DIL chip. No chance of anything shorting then.

Frank

[Geordie McBoyne]

Just returned to the workshop. I've removed the chip from the board and guess what? No ID, it's all been rubbed off.
So now I have to search for a suitable chip that does positive modulation video and AM sound.

Geordie McBoyne.