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Old 18th May 2017, 11:28 pm   #12
ricard
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Join Date: Mar 2006
Location: Lund, Sweden
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Default Re: Reel to reel tape recorder - bad capacitor?

Now that's an interesting design. Contrary to many early designs, it actually has a separate output stage and bias oscillator, however, the oscillator only supplies the bias via a slightly weird series circuit on the oscillator coil (transformer), and not the erase head, which is DC operated.

It looks like the variiable resistor in series with the oscillator provides some control over the bias in that it sets the maximum amplitude of the oscillator.

There certainly have been tape recorders which can record but lack an erase head, but I think that would mainly have been early (1950s) professional machines intended for on-the-spot reporting. The lack of erasure would have been only a minor annoyance, as the tapes would have been brought back to a studio, edited or transcribed, and then bulk erased before being sent out into the field again. For home use, which this machine certainly is, an erase head would have been mandatory in practice.

As for the lack of fast forward, I have seen that on several low-cost Japanese machines of that era, so it's not that atypical. Hey, you record then rewind to listen to what you recorded, what do you want to fast forward for?
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