Cassette head reversal problem

[N_Cook]

Well heads rotate perfectly well on both decks , Aiwa AD WX 888 but going in
batches , for each deck, either tape will not change direction , or will
work
consistently ie unreliably, mostly unreliable.
Drops into an illegal mode where both spools are powered in opposiste
directions and both pinch wheels are engaged , so likely to stretch or
break tapes. This action is initiated by a solenoid then PTO mechanics ,
perhaps one flip for normal play in whatever preceeding direction set before
stopping . Then longer pull or 2 pulls or something more complex
to change direction of play , not explored yet manually. Could this rely on
a timing adjustment somewhere that would apply to both decks ? I have
replaced both drive bands and the speed of both decks is as good as I can
get them via strobing and test tape.

 

[Mark Zacharias]

Well heads rotate perfectly well on both decks , Aiwa AD WX 888 but going
in
batches , for each deck, either tape will not change direction , or will
work
consistently ie unreliably, mostly unreliable.
Drops into an illegal mode where both spools are powered in opposiste
directions and both pinch wheels are engaged , so likely to stretch or
break tapes. This action is initiated by a solenoid then PTO mechanics ,
perhaps one flip for normal play in whatever preceeding direction set
before
stopping . Then longer pull or 2 pulls or something more complex
to change direction of play , not explored yet manually. Could this rely
on
a timing adjustment somewhere that would apply to both decks ? I have
replaced both drive bands and the speed of both decks is as good as I can
get them via strobing and test tape.

Normally this is only possible on a dual-flywheel single direction deck with
the belt threaded wrong.

If this one were to use motor reversal during reverse play, perhaps the
capstan belt could be threaded wrong after all?

Mark Z.

 

[N_Cook]

Normally this is only possible on a dual-flywheel single direction deck with
the belt threaded wrong.

If this one were to use motor reversal during reverse play, perhaps the
capstan belt could be threaded wrong after all?

Mark Z.

Then it would never work correctly. If anything when either deck works
correctly and considtently with multiple reversals then the tape is near the
end of its run, as if only allowable for reversing at the end of a side ,
but the problem will occur at the end of the tape sometmes, ie not reversing
..
Both deck bands were stretched, 1 band per deck ,not broken, so I could
mark the path of the bands to avoid that problem. Both motors run
continuously in one direction only.
It is dual capstan , one motor per deck. Unfortunately I have got waylaid
with more urgent stuff to look at.
I doubt its a RTFM thing (not present or repair manual), ie not allowed to
change direction in mid-tape as allowing a mode to stretch tape would be
very suspect.

 

[N_Cook]

There is no preset associated with the solenoid energizing area.
With bench 12V to the motor , manually pulling in the solenoid, under the
motor ,produces Play mode in normal direction for duration of soldenoid held
in.
A momentary pull and release flips the head rotor to reverse posistion but
deck stays in neutral.
A pull in , partial release, pull in and hold , engages Reverse Play.
Pull in momentary , full release momentary, pull in and hold , normal Play
I sometimes manually have been able to put it in the jam mode, easier if
driving the motor off 4V or so, but not at all obvious what is different in
that initiation.
I'm wondering if a wrong voltage is getting to the solenoid, either pull in
or maybe a negative pulse for the partial position. Whatever the solnoid
drive is, then if it is wrong then would explain why both decks are
affected, lack of lubrication or wear on the most used Play-only deck would
not throw up this jam mode on both decks.
I won't try scoping these solenoids as I've spent enough time on this
diversion and the owner is happy with just normal Play with both decks.
Perhaps both replacement bands are just not tight enough and slips on the
PTO pulley enough to mess things up. As the replacement bands were spot on
the existing motor speed preset via test tape and strobing , I will just
roughen the PTO pulley of both decks and leave at that. The slip clutch
inside the PTO pulley seems slack to me perhaps, something else to consider
if there should be a next time.

 

[N_Cook]

I don't know if it comes under William of Occam's raison (13th century
Occam, Surrey , England did not have razors at the time - later
mistranslation from French) or the more modern version K.I.S.S.

Roughening of the surface of the PTO pulleys returned reliable service for
normal/reverse play modes.