FAQ’s for Naks: ZX series

Question

When I adjusted Azimuth for the first time on my really nice Ebay zx7, I had to turn the knob more than a 2 whole turns (to the left) and finally the sign was OK.

Question: What is the normal span for this knob?

Answer:

Do not worry too much for two turns of adjustment, although it is more then usual.

First:

The purpose of the inclusion of this type of user-adjustment lies in the fabrication inaccuracy of the shells of the Compact Cassettes. The tolerances in production dimensions of these plastic containers have a direct effect on the tape travel, especially outside the center head aperture. This, unavoidably, has consequences for the alignment on three head tape mechanisms. (This type of alignment is superfluous for Reel to Reel tape recorders, as no shell exists.)

So; the required turns of the adjustment knob is directly related to the difference between the last played tape shells and the new tape you use. If it's the same brand and high quality tape the adjustment should be somewhere between zero and half a turn. If you use unfamiliar cheap tapes it might be double that amount. The quality of the tape shells might be deduced from the difference between sides A and B. Good quality shells show little asymmetric measurements and the A and B side will also be half a turn difference at max.

Second:

The adjustment of the record azimuth is done pure mechanically by a gear and a connecting BOWDEN cable. This is a long cable connecting the gears from the adjustment knob and the Record Head mounting/adjusting gear. This version of bowden cable has steel tape (which is fitted in a ladder-like blue plastic), and this steel tape moves the recording head. This bowden cable inevitably has some slack, which results in about a quarter turn slack on the adjustment knob. It might be more, due to wear and tear (and production tolerances once more, but now in the Nakamichi mechanism).

Third:

The Record Head Azimuth Alignment on the ZX series is fine and precise. The knob runs 20 turns at least, but the working range for serious tapes should lie within 1 turn only. Be very careful with setting the azimuth, as the connection between the worm-gear and the steel tape is quite weak, and it may happen they will disengage. Then you have to repair it... For this reason I heavily recommend to use the azimuth-knob very gently, do not turn it fast (let it settle), and do not turn it over the edge. If you feel that the knob is stopped, under no circumstances turn it with force.

Note that the Play Head Azimuth is assumed to be in correct location! Otherwise all is for nothing, you MAY make recordings sound good on your (the same) machine, but they will be mostly poor on other units.

Fourth:

The procedure to adjust the Azimuth needs considerable care and attention. Here it is:

In record standby mode, push in the azimuth adjustment big button to start the calibration and have access to the azimuth knob, wait a few seconds for the azimuth lights to stabilize, then turn the knob in 1/4 turns in the direction away from the lit red light until the center green light glows steady. Wait a few seconds with each turn you make.

The bias and levels adjustments have indirect effect on the Azimuth Adjust procedure. If they are off a lot, the lights of the Azimuth Adjust will not lit or stop after a second. In this case the Level adjustments have to be set to the correct position and Azimuth lights will work again. Maybe the bias must also be adjusted first if it is way, way off. Finalize the levels and bias adjustments after the correct Azimuth has been attained to get the correct end result.
With all of this, be sure you have the right tape type button selected before you start and that your dolby is set to off, multiplex filter (MPX) is off and monitor is set to tape position. Be sure you are adjusting the small knobs directly in the column under the tape type button, and horizontally in the row with the levels or bias button.

The adjustment result is fed back to you on the two left - right diode lights and the green center diode light. The comparator circuit controlling these lights can unsettle due to the age of the electronics involved. That’s why I do check the results listening to the recordings themselves.

At last:

Listening to the recording via the tape monitor very carefully will reveal the actual state of azimuth adjustment. Listen to voices panned in dead center on popular (POP music is basically recorded as multi-mono signals and voices are panned in dead center mostly) recordings and listen repeatedly for the centering of the voice before tape and after tape (headphones might help here, leading an absolute mono feed to both channels will also help). Adjust the azimuth (a few turns!) when recording and keep listening to the centered sounds changing characteristics. Do this back and forth a few times and you will get the feel what the adjustment does and how fine you can optimize the effect.

In short; Try to experiment somewhat. This is how you can reach the ultimate result ....