Re: Hitach TRK-3D30E Help!
Hi Chris,
I have the March-89 servicemanual only and it shows the cap. to be 47uF as you say.
I believe there is good reason for it to be 47uf as it's the coupling capacitor for the inverting amplifier-section of the push-pull amplifier for the sub-woofer.
You want the low-frequency cut-off to be low for the inverting amp., so it will follow the non-inverting amp. as close as possible and that indicates 47uF, not 4,7uF.
Take a look at the input signal-path for the signal. From the summing junction of R511/R512 the mono-signal passes through the low-pass filter R512~R514/C511, 512, 517 stripped of anything but the lowest frequencies.
In any case, this sub-woofer amplifier is only active when the 3D switch S501 os on, so it has no influence on the general sound of the stereo-amplifier.
Unfortunately Hitachi choose the reverse the inverting and the non-inverting amplifier sections of the IC compaired with the original Sanyo data-sheet for LA4558. You should have a look anyway.
Rgds,
/Torben
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