The Pineapple standards converter.

[ppppenguin]

Is there any eveidence of a 3.5MHz sound modulator? Can you sketch out the schematic with the unknown chip as a black box?

Is this actually a worthwhile repair? If you or somebody else has a spare modulator around might it be easier to supply that instead? Or simply suggest giving up using the Pineapple and get an Aurora?

[Murphyv310]

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.

Just what I thought.
So many items that are not mainstream seem to be made like this. I never see the point of this as often the original manufacturer goes bust or has no intention of allowing a third party to effect a repair.
Without beating my drum once again, electronic repairs is a dead loss.
I would think that finding a suitable chip is like finding a needle in a haystack. Darryl might help though or you could of course construct a suitable modulator with two MC1374's.

[Geordie McBoyne]

Well worth considering is the ETF modulator for 405 line TV, uses two MC1374 ICs.  Compact and works very well.

From the ETF:    http://www.earlytelevision.org/405_modulator.html

Geordie McBoyne.

[Geordie McBoyne]

Is there any eveidence of a 3.5MHz sound modulator? Can you sketch out the schematic with the unknown chip as a black box?

Is this actually a worthwhile repair? If you or somebody else has a spare modulator around might it be easier to supply that instead? Or simply suggest giving up using the Pineapple and get an Aurora?

I'm doing this job for a customer. The Pineapple itself is working fine, it's just the modulator that's the problem.
I've traced out the connections to the chip, I'll draw a diagram later and scan it.  I reckon that it works on the 3.5Mhz sub-carrier principle.
Converter and modulator are assembled into an old modem case.  Makes for a compact unit.

Geordie McBoyne.

[ppppenguin]

I've had an email from Malcolm Everiss, of Domino converter fame:

Hi Jeff,


Saw David Boynes was nattering about pineapples and a German modulator, way back in the Domino days I did extensive investigations into all sorts of options for modulators, IC's and such.

[...........], 
The chip on the data sheet has the correct pin outs and pin functions, the German modulator chip is referred to as 'Special IC SO244' the data sheet for the TDA5664 fits the function for all but one thing... the sound is FM , it could be that there is another chip type in the range that 
has AM sound ?,  but I wondered if the use of an FM subcarrier with wide enough modulation to give slope detection in the receiver was what is being done ?.

[....................]

PS maybe the ref to IC SO244 could be part of an incorrectly stated SO14-4 package ?

hope that is useful,

Malcom

He attached some relevant pages from 405 Alive which can be seen here at p39 et seq: http://www.bvws.org.uk/publications/405a...hp/issue11

He also attached a TDA5664 data sheet which can be obtained here: http://www.alldatasheet.com/datasheet-pd...A5664.html

David, I've sent you an email.

[ppppenguin]

I believe this to be the German modulator, taken from the issue of 405 Alive that I referenced above.

Full marks to Malcolm for digging all this out and getting in touch.

[ppppenguin]

The main mystery is how sound modulation is done. Clearly intercarrier but how do they get AM? Malcolm suggested a different but related chip might exist. Or it's actually FM but slope detected in the receiver. Or maybe the chip is being used in an unorthodox way to get AM. Can't see this happening as the sound is going into pin 13 as on the data sheet for the TDA5664.

My German is almost non-existent and I can't quite make out all the handwritten words on p41 of that article to type in google translate but...

The sound modulation is connected at pin 13 (Amplitude with pin 1 adjustable) ????????????????? L2 ????? carrier frequency.

L2 and C5 set the sound frequency. The example circuit on the TDA5664 data sheet shows a 10K damping resistor across the sound LC tuned circuit. This is omitted on the Meier design. I wonder if this encourages amplitude modulation, which would be spurious in the intended application of the chip, at the expense of FM.

[Murphyv310]

Hi.
All very well but is this chip not now NLA?

[ppppenguin]

It may well be NLA but at least we have a good idea of what we're dealing with. It's not even 100% certain that we've got the right chip as there may have been a slightly different device specifically for AM sound.

This clearly isn't the device we're looking for but it suggests Siemens made soemthing to do AM sound: http://pdf.datasheetcatalog.com/datashee...-A5179.pdf

PS: Getting closer. TheTDA5660P does AM and FM sound but is 18 pin.