First of all, do not try to make adjustments "just for fun". Your recorder might very well be in excellent shape
(until you started to "adjust"....).

However, maintenance also means to check that it works properly, and by checking and measuring you might find that
no adjustments are necessary!

To do the job properly, you need a service manual, a test tape, and some instruments.

Some measurements though, can be done with just an AC Voltage meter, if it can handle the frequency.
A simple one may handle frequencies between 30-300 Hz, while a better one handles over 20000 Hz.
Have a look in any catalogue and compare different DVMs.
As I said before, do not adjust things if it is not necessary, but you can still measure and check while you keep your fingers away from any adjustment screws...

CLEANING
Before any checks are made, be sure that you have cleaned the heads and tape transport parts properly.
Otherwise, the measurements will have no value at all.

DEMAGNETIZING
By using an electric "degausser", you can remove magnetic energy that has built up in the tape transport mechanism and heads.

TAPE TRANSPORT ADJUSTMENTS
This is the the next step. Here you check that the tape runs smoothly and that the functions for playback, rewind and so on
works. If adjustments are necessary, one usually needs the service manual to adjust brakes or the pinch roller pressure
so that it meets the specified values.
 

HEAD ADJUSTMENTS
1. Head Height  (picture 3 above).
The first check is to see that the tape runs where it should across the heads.
The easiest way to inspect this, is to use a piece of clear tape that you sometimes find at the beginning of the tape.
By looking through the tape, you can see if the tracks are "centered".
If not, there are adjustment screws to align the tape guides.
One problem you could encounter, is if the head is so worn that there are grooves on the head.
Then the tape will either find its way into the groove even if you try to adjust, or...
the tape will not be in touch with the head properly if it runs beside the groove.

2. Checking the azimuth (2).
This is a test where you need an oscilloscope and a test tape.
If the azimuth is not correct, it will lead to a time difference between the tracks.
For a detailed discussion on this subject...(Read more in detail here).

3. Tangency adjustment (4).
This is a check that can be performed with no instruments other than the VU meters.
If the tangency angle is not correct, you will not get the maximum signal from the tape.
The adjustment is done by using a test tape with a steady tone (or record a steady tone).
As you then play the tape, you adjust the heads while watching the VU meter for maximum output.

WORN HEADS
Maybe the heads are so worn out that they need to be changed?
Here is a photo showing heads for my Revox B77.

Click here to see full size photo.

The left head is brand new, and the right one is worn.
(You can see there is a flat surface across the center of that head, about 5 millimeters wide).
 
 

OTARI MTR 15

Back to  Recorders startpage
Next page about Electrical adjustments