-=> Roy J. Tellason said to Greg Mayman
 -=> about "*BIG* TRANSISTORS" on 02-12-04  04:06.....

 RJT> No,  the data sheet specifically mentioned vcr and audio cassette
 RJT> applications. I can see reversibility being a good thing if you're
 RJT> running a tape cassette and have a bidirectional capability in the deck
 RJT> -- you'd have the mechanism switch capstans, but the motor would also
 RJT> need to spin in the other direction.  VCRs? Hm,  that's a little more
 RJT> difficult, I'm not that up on the mechanicals of those.

The only reversable cassette player I've looked inside has the
motor running one way all the time. The belt drive is arranged so
the two capstans are both turning at all times, but in opposite
directions. The pinch wheels and reel feeds are controlled by a
solenoid operated mechanical flip-flop.

The only place I can think where you'd need a reversable motor
with braking in a VCR is in the loading mechanism. Years ago I
saw a cassette player that could load and change bewteen a stack
of cassettes -- that would have needed a loading mechanism.

One intersting thing that the owner told me was that he could
have bought an add-on that would take each cassette as it was
ejected, and move it to the top of the stack, flipping it over on
the way. So you could have continuous playing of up to 10
cassettes, all the "A" sides first then all the "B" sides, then
repeat...

 GM> I remember them!
 RJT> Yeah,  weren't they nifty?  :-)

Yes. We don't seem to have any true analog displays these days.

 RJT> Vaseline?  First time I've heard of that being used for the purpose...

I heard of one couple that used it for sexual purposes... they
greased the bedroom doorknob to stop the kids from bursting in.

I always keep a jar handy... for strictly technical purposes you
understand.

 RJT> I've used all sorts of assorted spray cleaners over the years.

They work for a while, but they tend to dry up. An inert grease
is the best as it will coat the track. The wiper can press the
grease aside (if it is not too thick) and the grease will reform
the seal behind the wiper.

 RJT> Transformers fall into the category of inductors,  a class of
 RJT> components that I've seldom gotten along with over the years.  :-)

They can be a real bugbear.

I once salvaged a transformer that had burned out, only because
it had a low loss core. The laminations were made in one piece in
the usual [|] shape but the only break was across one end of the
centre leg where it met the outer ring. I cut the old windings
out of the former and rewound it to 7 turns/volt to suit the core
area. but I must have made a miscount somewhere as the secondary
gave a lot lower voltage than it should have.

When I did some tests I found it was closer to 10 turns/volt!

I never could use it for the purpose I intended it for as there
wasn't enough room left to get the volts I needed and it was too
much trouble to remove the laminations, strip off the secondary,
strip some of the primary and rewind the secondary.

That was an interesting project -- an audio amplifier with a
class AB output driving a class C booster, using all discrete
transistors.

The performance was quite good. The distortion was surprisingly
low considering the output stage, but I can't remember the
figures now.

   ,-./\
  /     \ From Greg Mayman, in beautiful Adelaide, South Australia
  \_,-*_/    "Queen City of The South"    34:55 S  138:36 E
       v

... I cut down trees, I eat my lunch, I go to the lavatory.
___ Blue Wave/386 v2.30

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