JC wrote:



I'm not really sure how much use this meter will be anyway without a
calibration tape. Using the output signal and recording on a machine of
unknown quality then replaying the tape is just compounding errors.



** W&F test tapes simply have a pure tone recorded at 3 or 3.15 kHz.

In the real world, people normally record and play back on the SAME machine - so it makes sense to test a recorder that way using a sine wave generator as the 3kHz source. There will be a higher reading on the W&F meter than given in the maker's specs when frequency deviations add in the same direction during playback. If the machine allows simultaneous record and play, that makes the process all much easier.

FYI:

I regularly do repairs on Roland tape echoes ( models 201,301 & 555 ) which all have a pretty high quality transport with ball race tape guides and a direct drive capstan motor with large pinch roller. Testing is normally done with a square wave input at 500Hz, a single playback head selected and the output monitored on a scope. If the generator is linked to the scope's external sync input, any serious W&F is pretty obvious on the screen.

Using a square wave quickly reveals if the high frequency response is good and consistent for all playback heads, so checking the head alignment. Servicing these machines involves a lot of cleaning and polishing of the tape path and heads plus resurfacing the pinch roller when it has become hard and glazed. The tape's back tension is a critical adjustment as it affects both amplitude and W&F in the playback.

Sometimes the main ball race in the capstan motor has to be replaced - when there is severe W&F or a steady tape speed cannot be maintained.

Lotsa fun.


...... Phil