schematic symbol question

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schematic symbol question

Post by arkestra » Fri Jul 25, 2008 4:44 pm

Hey, what in the hell is U13? I was recapping a capstan motor and in my haste to test it I shorted out Q6 and an electro. (long story) Q6 cracked and went up in smoke and U13-14 literally popped. Q6 is easy to replace but U? what is that? it looks like a transistor or an inverter on the schematic. They both have C124 E.S.V. printed on them.

(bad) Schematic below.

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Post by RefD » Fri Jul 25, 2008 5:11 pm

unless you have a parts list that correlates to the schematic then your guess is as good as mine.

the symbol and position suggests some kind of logic function, maybe related to the transport.
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Post by Nate Dort » Fri Jul 25, 2008 8:32 pm

Looks like a digital gate, probably a "NOT" gate (also called an inverter). C124 doesn't look like it corresponds to anything though. There's nothing else printed on it? What type of package is it in?

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Post by arkestra » Sat Jul 26, 2008 12:31 pm

the case looks like a smaller transistor. There are 3 radial leads and the case itself is symmetrical. it is not flat on one side and curved on the other like a transistor. ill try and search for a parts list or ask tascam. . .

The Scum
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Post by The Scum » Sat Jul 26, 2008 1:36 pm

It sounds be an inverter of some sort.

The triangle with the little circle makes a logic inverter, and the "N" probably means "NOT" gate.

But the line across the triangle means something, and my foggy brain isn't telling me what at the moment.

Since it's got 3 legs, and effectively no V+ connection, It starts to look like an open-collector inverter.


Since it's a Tascam schematic, I went and flipped through my MS16 schem to see if the part was there...and indeed it was. On the page where they show what's inside the chips, there's a 3-pin device with the name "DTC124N." It's a pre-biased transistor, with an open-collector.

I don't find any DTC124N's in a quick google search, but there are a number of DTC124x variants around...

In he schem itself, is there a section where they say "U3 = XYZ?"

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Post by suppositron » Thu Jul 31, 2008 12:50 pm

That actually looks like a tri-state device. It has very high impedance when inactive and very low impedance when active (or vice verse). Pretty much used as a connection breaker in this case.

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