Take your recorder to a reputable audio equipment service organisation who should have an Industry Standard test tape and the necessary instrumentation to very accurately set the azimuth of the head.

If you have some understanding of electronics and have a milliammeter you could lash up a rig using a 3.5mm mono plug (e.g. Tandy 284-286/7) to plug into the EAR socket of your recorder, wired with two leads; the lead which you have connected to the stem of the plug should then be connected to the negative terminal of your meter.

The other lead should be connected via a diode (e.g. Tandy 276-1101) to the positive terminal of the meter but be sure to connect the marked end of the diode to the meter. A resistor should then be connected across the leads from the pug; its value will be dependent upon the scale of your meter - try 1K for a start.

You need a cassette containing a good quality program recording - if you have the Electron Introductory Cassette this would probably be the best choice. The adjustment of the azimuth setting of the head is by turning a small screw which is accessible through a hole in the top cover of the recorder when the head is in the play/pause/record position.

You will need a jeweller's screwdriver for the hole is usually not more than about 3mm diameter. Having set everything up and with the volume set to minimum, run the tape. Now increase the volume until you have a reading peaking in mid-scale then turn the screw one way until the reading is markedly less.

Be cautious - a half turn should suffice. Now turn in the other direction beyond the original position until the reading is similar. A position mid-way between the two rotations should be optimum. Criss-cross this position several times to check that you have the maximum possible reading.

When adjustment is complete, apply a minute dab of Loctite or similar to the head of the screw to prevent casual rotation. N.B. If your recorder has tone control then set this to maximise the treble and minimise the bass. If you are using a stereo recorder the procedure should simultaneously achieve correct azimuth alignment for both channels but using a mono plug will give you only the signal from the left channel.

The best channel to use could be established using a three wire/stereo plug (e.g. Tandy 274-284) set up but the choice would not necessarily be the best for all tapes because of possible variation in the relationship of the heads to the track of the mono recording.

If you do not have a meter then plug in the conventional tape of earplug and listen to the sound as you rotate the screw. The optimum setting will be when you hear the most crisp sound. Do not be misled by the overall sound - remember the computer likes the higher frequency response.