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Who wants to peek inside a TDA1170?


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SE and Classic analogue board (and Lisa video board) technicians will know the TDA 1170 chip as one reason your display can collapse into a narrow horizontal line (see for example page 165 of The Dead Mac Scrolls). It's a funny-looking device: meant to handle more voltage and current than your typical IC, it has these thick heat-dissipating wings coming out of the side of the DIP. I've often wondered whether these might be interesting to look at on the inside as well.

 

There are various people out there who are skilled at decapping ICs and taking photos of the die inside, and I've been contemplating sending one of my TDA 1170 spares to one of them. These chips are not made anymore, but they are not so rare (they were used in plenty of TVs and monitors). Still, I thought I'd ask the community two questions:

 

1. Yay or nay: decap what's likely a perfectly good chip that may have interesting insides owing to its unusual job --- but are they interesting enough to be worthwhile?

2. Has someone held onto a broken TDA 1170 from an earlier repair --- and would they care to donate it to science? To me this is optimal: we get to see the engineering and the failure.

 

If you say "yes" to 2, let me know. Decappers often request that you pitch in to their costs, and I'm happy to cover it for this one, so presumably all you'd need to do is drop the chip in the post.

Edited by stepleton
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On 2/24/2021 at 10:50 PM, stepleton said:

SE and Classic analogue board (and Lisa video board) technicians will know the TDA 1170 chip as one reason your display can collapse into a narrow horizontal line (see for example page 165 of The Dead Mac Scrolls). It's a funny-looking device: meant to handle more voltage and current than your typical IC, it has these thick heat-dissipating wings coming out of the side of the DIP. I've often wondered whether these might be interesting to look at on the inside as well.

 

 

I think all of these preservation projects are valuable, unless there's thousands of these available out there.

 

The attached datasheet might help make a good start at this.  There's a block diagram and a transistor level schematic, although the characteristics of the transistors are not specified.

 

TDA1170.pdf

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I'm not sure that decapping the chip will tell us too much from a restoration perspective --- maybe if we examine a failed device, we can learn something that can help us mitigate those kinds of failures, perhaps some kind of hardware mod. But I expect it'd be hard to fill in missing data on the equivalent schematic based on what you see in a die photo.

 

Even if it is possible to reconstruct this information, it may not be necessary to do that to fix a broken SE. The Mac 128k, 512k, and Plus generate the same vertical sweep using discrete components, so if the world runs out of TDA1170s, then it's probably fairly easy to design and build a substitute --- much easier than recreating one of Apple's custom ASICs. (The hard part may be finding a place for it to fit.)

 

I suppose the main purpose of opening up one of the chips would just be to see how it was made, or what the designers had to do to make a chip that could work in that application. More education and entertainment than preservation. Still, I wanted to get a sense of how the community felt about the idea.

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