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Thread: Erase head question

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    Erase head question

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    I was a bit surprised a while ago looking at the erase head of my Tascam 244 - it seems the track layout is staggered and not in-line. I wondered why this is? I remember seeing that bias currents for some erase heads can be as high as 70 mA and working voltages as high as 20V or so. This would mean something like a Watt or more being dissipated for each channel. Is this heating effect the reason for the staggered design and is it common in multitrack machines? I'm surprised with this much power it doesn't lead to heating up of the tape when set on pause!

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    Stereo erase heads are often inline but with multitrack ones they are usually staggered. I seem to recall that the erase head on my MSR-24 is NOT staggered, which surprised me at the time.
    I'd have to check that when I get home. And yes, I suspect it's to do with the heat dissipation. That's just a guess, though. It might also be to prevent the fields interacting somehow, the erase field most likely being the strongest.

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    Okay, I was clearly hallucinating about the MSR-24 having a non-staggered erase head.
    However, this may be of interest:
    https://www.gearslutz.com/board/low-...0-8-heads.html

    ...at a guess, they went with a non-staggered design initially and then changed it later, presumably after it caused problems.

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    Thanks jp. I'd never thought about erase heads getting "hot" before but maybe they do....

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    The original erase headstacks on the 24-track Ampex MM-1000 weren't staggered. That was in the very early days of 2" 24-track. They had problems with them cracking due to the heat...later versions were staggered. Crazy stuff.

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    Is the current to the erase head cut in pause mode in most decks? Otherwise there would surely be tape damage?

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    Here's some Telefunken heads.

    The 16-track head doesn't seem to be staggered
    Telefunken M15, 16 track 2 inch head in wooden box, NOS, nr.2 • EUR 1.750,00 - PicClick DE

    The 24-track head is weird - it seems to be two offset 12-track heads.
    Telefunken M15, 24 track 2 inch head in wooden box, NOS, nr.1 • EUR 750,00 - PicClick DE

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    Regarding the Telefunken erase head, that is how some manufacturers handled it, especially early on...the staggering. It's the same as IRIG data recorder record/play heads. Actually it's the same idea as the Tascam cassette 8-track record/play head.

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    Thanks guys. I'm still intrigued by how much power is used for erasing!

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    I don't know the answer to that. And as to other question about pause mode...I guess I don't know that either. You'd have to look at the schematics to be sure. My hunch is that the answer is "yes", the current to the erase head is cut during pause mode. You could always measure the output of your bias amp in rec/play and then see what happens when you pause for your particular machine.

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