Adjusting internal Bias?

[valman13440]

My brother gave me a Mint Sony TC-K555 3 head dual capstan cassette deck that was made in 1982.The deck does have a bias fine control but it only works for normal bias type 1 cassette's.Is there any way to adjust the bias inside the deck to get better high end out of High Bias type II tapes?Is there any kind of bias trim pot that can be adjusted inside the deck?Thanks for any help.

[Scorpion8]

There should be, but you'd need the SM and a bunch of silly-'scopes and stuff to re-adjust that. Almost all the decks has trim pots on their PCBs to apply fine tuning during calibration. Get yourself a copy of the SM and check it out, and then a good trusty tech.

[valman13440]

Thanks,If i find the trim pot that adjusts bias for type II tapes can i adjust it by ear?Turning the trim pot until the treble is were i like it?

[Web Police]

Are you sure the deck doesn't have a button to push for type II tapes. Or maybe it has the pivoting arms in the deck well that sense the holes on the top of a cassette, and they are malfunctioning?

[Scorpion8]

Vintage Cassette has a pic and some details here (http://www.vintagecassette.com/Sony/TC-K555). It says 4-position tape selector which indicates it would set the bias and equalization whenever the right tape type is selected. What's it doing or not doing?

[valman13440]

The deck does have 4 buttons one for type 1 one for type II one for type III and one for metal.The bias fine control only works for the type 1 position.The deck sets the bias automatically for whatever type of tape is inserted (After pushing the appropriate tape type button) but i would like to get a little more high end out of the high bias tapes which a manual bias control would do if you use less bias.Since this deck was factory calibrated and the bias can't be manually adjusted for all but type 1 tapes, it sounds a little dark in the high end and i would like to add a little sparkle to the top end.

[Scorpion8]

How do you know the bias fine adjustment only works for Type-I tapes? It normally should work for any tape selected. What tapes are you using? Something to try would be selecting Type-III for a Type-II tape, as it used (if I recall correctly) equalization for a Type-II tape but bias for a Type-I tape. Lemme go double check that before I step in it....

[valman13440]

The manual says bias fine adjustment only affects the type 1 position.I even tried adjusting the bias fine control in the type II position with the deck in tape monitor of course and it did not affect the sound in either the + or - position.I then tried the bias control with a type 1 tape and the bias control did work so the manual is right.It is strange that sony would put a bias fine control on a deck and make it only useful for normal bias tapes.I'm pretty sure that this deck's bias was factory calibrated back in 1982 to tapes that were made at the same time 1982. Oh yeah,i am using pretty much TDK SA and SA-X tapes..

[stuwee]

Interesting, while I'm not familiar with your deck, I'll venture that is has some kind of adjustment internally for the other types of tape. If it does I'd pick just one type of higher bias tape and set it by ear for that, in fact, I'd take it one step further and buy as much of that tape as possible, you know from the same batch, since you can't really fine tune it later without diggin' around inside.

Or maybe, use another deck to record that has the capablity and sounds good played on the Sony. Kind of the long way round but.....

[Scorpion8]

The manual says bias fine adjustment only affects the type 1 position.I even tried adjusting the bias fine control in the type II position with the deck in tape monitor of course and it did not affect the sound in either the + or - position.I then tried the bias control with a type 1 tape and the bias control did work so the manual is right.It is strange that sony would put a bias fine control on a deck and make it only useful for normal bias tapes.I'm pretty sure that this deck's bias was factory calibrated back in 1982 to tapes that were made at the same time 1982. Oh yeah,i am using pretty much TDK SA and SA-X tapes..


Lemme pose a few questions:

1. When was the last time the heads were demagg'ed, and are they done so routinely?

2. Have you kept the heads clean, both of which can destroy or muddy the top end response.

3. Are you the only owner? Is it possible the previous owner (if any) fiddled with the calibration?