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Help identifying transistor array "M8715"

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tomizett

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Long shot here folks, but...
I'm trying to identify a component in a circuit that I'm working on (it's the function generator mentioned in my other thread under "repair"). It's an 8-pin PDIP, marked "M8715 <newline> J412"; the manufacturer's logo is a couple of vaguely n-shaped squiggly lines one above the other - is that National Semi?
It's identified on the silkscreen as "TR1", so I assume it's a transistor array. It certainly measures out like one, looking like 2xNPN but with a resistance of about 500k in parallel with (what appear to be) C and E. Only 6 pins are connected.

I'm just wondering if anyone can confirm what this might be, in case I'm mistaken. I'm particularly curious about this "resistance" showing up across C and E. It appears to be wired as an LTP.
Actually, I suspect that the part is not faulty but it would be nice to have a more definite idea of how it should behave.

Thanks in anticipation...
 
I don't think there were many "transistor array" parts, but look here: **broken link removed**

M8715 MAY be a date code: 15th week of 1987

Oops, I didn't catch the 8 pin DIP. Dual transistors are possible.

I did find a J412 FET in a DIE package.n Not sure if it's dual.
 
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I haven't looked it up or anything, so could be way off the mark here. If the device is anywhere near the power supply or sub supply, could it simply just be a 7815 voltage regulator in a pdip package?
 
Well... I've just repaired the original fault, which was simply down to a dry joint.
I'm pretty sure that it's a dual NPN as I originally suggested. I substituted a pair of BC337s, and the ciruit just about worked - albeit terribly badly. The resistance between C and E seems very unstable when measured with a meter - drifty with temperature maybe? Could it even be something more obscure like a UJT?

Whatever it is, let's just hope it doesn't fail anytime soon.
Thanks for the suggestions though.
 
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