Help with audio cassette recorder self-stopping

[Robert Inder]

I have a Denon DR-M44HX --- a (fairly high-end) audio cassette deck
(remember them?) that has suddenly started working for only about a
second at a time.

A couple of days ago I tried to play a tape
that had not been played for years, and the deck kept stopping. I
thought maybe the tape was too tight, so wound right through it (I had
to press the "wind" button many times) and back, and then it played
the whole tape perfectly.

But the following day, it had turned into a "hard" failure: it would
wind or play for about a second, and then both reels of tape would stop
moving and the heads retract, with the same kind of "click" that it
makes at the end of the tape.

I tried cleaning the heads and rollers (head cleaning fluid): there
was no visible muck, but to my delight, it seemed to fix the problem.

Except that today, it is back: the machine plays (or winds) for a
second or two, then stops.

Re-wind is also affected, but slighly less severely: it will sometimes
go for three or four seconds.

The (digital) tape counter is sort-of working: during "play" it
clocks up roughly one second each time it plays (which is about right).
But the counter only changes by about a second per second during
wind and re-wind, as well.

I'm guessing that it is something to do with the machine not
properly detecting that the tape is moving and activating the
"end of tape" shutdown. But that said, the tape counter IS
changing at least a bit, and the tape does wind/play properly...

Has anyone got any ideas?

Before I start taking it apart, I am hoping that somebody who can
remember such "ancient" devices could tell me what sort of thing I am
looking for...

Robert.

 

[techforce]

You Will have to Remove the Deck Mechanism and Load in a Tape , press Play ,
and look carefully see what is Mechanicly Happening to activate Auto Stop.

Sometimes a small Plastic Lever cracks, or the Tension on the Take-up Reel
is too tight, and Activates Auto Stop on som eof the Cheapo Brands. Since
yours sounds High - End, it likely could be an Idler Tire, or a Belt too.


|
| I have a Denon DR-M44HX --- a (fairly high-end) audio cassette deck
| (remember them?) that has suddenly started working for only about a
| second at a time.
|
| A couple of days ago I tried to play a tape
| that had not been played for years, and the deck kept stopping. I
| thought maybe the tape was too tight, so wound right through it (I had
| to press the "wind" button many times) and back, and then it played
| the whole tape perfectly.
|
| But the following day, it had turned into a "hard" failure: it would
| wind or play for about a second, and then both reels of tape would stop
| moving and the heads retract, with the same kind of "click" that it
| makes at the end of the tape.
|
| I tried cleaning the heads and rollers (head cleaning fluid): there
| was no visible muck, but to my delight, it seemed to fix the problem.
|
| Except that today, it is back: the machine plays (or winds) for a
| second or two, then stops.
|
| Re-wind is also affected, but slighly less severely: it will sometimes
| go for three or four seconds.
|
| The (digital) tape counter is sort-of working: during "play" it
| clocks up roughly one second each time it plays (which is about right).
| But the counter only changes by about a second per second during
| wind and re-wind, as well.
|
| I'm guessing that it is something to do with the machine not
| properly detecting that the tape is moving and activating the
| "end of tape" shutdown. But that said, the tape counter IS
| changing at least a bit, and the tape does wind/play properly...
|
| Has anyone got any ideas?
|
| Before I start taking it apart, I am hoping that somebody who can
| remember such "ancient" devices could tell me what sort of thing I am
| looking for...
|
| Robert.
|
| --
| __ To avoid the spam trap, mail me
| |_) _ |_ _ ._ |- | _ _| _ ._ at bcs.org.uk, not deadspam.com.
| | \(_)|_)(-'| |_ || |(_|(-'| '
| Best viewed in Ebriated.

 

[William R. Walsh]

Hi!

If the tape counter is not running, this may make the microcontroller
"think" that the tape is not advancing properly. This will likely cause a
shutdown because lack of tape reel movement usually indicates that a tape is
in the process of being eaten.

Detection of this can be done several ways. Hall effect sensors and optical
sensors (not unlike the ones in older computer mice that don't use an
optical (red light) pickup) are at least two ways of doing this. Either the
detectors or the controller could have experienced a failure.

Hopefully that gives you some ideas for troubleshooting. Good luck!

William

 

[Chuck]

I have a Denon DR-M44HX --- a (fairly high-end) audio cassette deck
(remember them?) that has suddenly started working for only about a
second at a time.

A couple of days ago I tried to play a tape
that had not been played for years, and the deck kept stopping. I
thought maybe the tape was too tight, so wound right through it (I had
to press the "wind" button many times) and back, and then it played
the whole tape perfectly.

But the following day, it had turned into a "hard" failure: it would
wind or play for about a second, and then both reels of tape would stop
moving and the heads retract, with the same kind of "click" that it
makes at the end of the tape.

I tried cleaning the heads and rollers (head cleaning fluid): there
was no visible muck, but to my delight, it seemed to fix the problem.

Except that today, it is back: the machine plays (or winds) for a
second or two, then stops.

Re-wind is also affected, but slighly less severely: it will sometimes
go for three or four seconds.

The (digital) tape counter is sort-of working: during "play" it
clocks up roughly one second each time it plays (which is about right).
But the counter only changes by about a second per second during
wind and re-wind, as well.

I'm guessing that it is something to do with the machine not
properly detecting that the tape is moving and activating the
"end of tape" shutdown. But that said, the tape counter IS
changing at least a bit, and the tape does wind/play properly...

Has anyone got any ideas?

Before I start taking it apart, I am hoping that somebody who can
remember such "ancient" devices could tell me what sort of thing I am
looking for...

Robert.

This particular deck uses optical detection in the autostop circuit.
The ic which the detector is wired to used to fail very regularly.
There was a circuit revision to alleviate this problem but I don't
remember what the mod was. I would try to find a Denon warranty
station that was in business in the late 80s. They should have the
mod sheet. Chuck

 

[Robert Inder]

Subject: Re: Help with audio cassette recorder self-stopping
Date: Mon, 12 Jul 2004 13:28:43 GMT

On 11 Jul 2004 14:10:22 +0100, Robert Inder <[email protected]>
wrote:

This particular deck uses optical detection in the autostop circuit.
Oooh...

The ic which the detector is wired to used to fail very regularly.

A failed IC would be a bummer.

But the fact that it was initially intermittent makes me wonder.

As does the fact that messing about with head cleaner seemed to have
an (albeit temporary) effect...

Can you say a bit more about this optical detector?

What does it look like? Is there some kind of "tape-side" lens that
could have got mucky over the years?

What does it "look" at? Is it looking for the transparent leader? Or
detecting motion in some way?

There was a circuit revision to alleviate this problem but I don't
remember what the mod was. I would try to find a Denon warranty
station that was in business in the late 80s. They should have the
mod sheet. Chuck

Robert.

 

[b]

look around the area of the tape up spool for either a magnetic or
optical motion detector. Often (at least with older units) there was a
thin rubber drive belt connected to the take up spool and either the
tape counter directly, or another sensor wheel which tells the
electronics what the mechanics are doing . If the unit has been in a
smoker's house chances are you simply need to clean the rotation
sensor (sometimes a thin glass reed switch, sometimes a rotating disc
with black and silver sections and a light source/sensor. maybe even
under the spool? these are just guesses so try and get a service
manual.

Ben

 

[Chuck]

A failed IC would be a bummer.

But the fact that it was initially intermittent makes me wonder.

As does the fact that messing about with head cleaner seemed to have
an (albeit temporary) effect...

Can you say a bit more about this optical detector?

What does it look like? Is there some kind of "tape-side" lens that
could have got mucky over the years?

What does it "look" at? Is it looking for the transparent leader? Or
detecting motion in some way?


Robert.

The take up reel is gear driven and the optical detector is under the
take up reel. By pushing the tape in switches, the deck can be put in
play mode without a tape in it. See if the take up reel stalls before
the deck shuts down. If so, the reel motor may be worn out. These
units often came from the factory with too much takeup tension. If
the motor needs to be replaced, the reel motor drive electronics may
have to be modified. Chuck.

 

[Robert Inder]

Subject: Re: Help with audio cassette recorder self-stopping
Date: Tue, 13 Jul 2004 13:53:18 GMT
:
:

The take up reel is gear driven and the optical detector is under the
take up reel....

Thanks for your suggestions.

I took off the cover and front panel (which really stiffens up the
chassis!) and decided to power it up to see what I could see (before
I started trying to remove the tape transport), and the <expletive
deleted> thing played perfectly!

So I put it back together and into the shelf and...

it auto-stopped after 2 seconds. Two minutes later, after tidying
away the trailing cables, I powered it up again, and it worked
perfectly, and has done so for the last three hours.

So it is quite definitely an intermittent fault! So I'm definitely
going to follow your suggestion. I've tracked down a copy of the
(pay attention, Google!) Denon DR M44HX service manual, and once
that comes I'll have a go at fixing it properly.

Thanks again for your help.

Robert.

 

[Pinchy]

look around the area of the tape up spool for either a magnetic or
optical motion detector. Often (at least with older units) there was a
thin rubber drive belt connected to the take up spool and either the
tape counter directly, or another sensor wheel which tells the
electronics what the mechanics are doing . If the unit has been in a
smoker's house chances are you simply need to clean the rotation
sensor (sometimes a thin glass reed switch, sometimes a rotating disc
with black and silver sections and a light source/sensor. maybe even
under the spool? these are just guesses so try and get a service
manual.

Ben

I once had a similar problem with another type of cassette deck. I
had it repaired by a service center and the only problem was that the
magnetic sensors indicating the start / end of a tape had to be
replaced.

 

[Mark D. Zacharias]

Magnetic sensors for start and end?

If that's exactly how they put it to you, they may have "put it to you".
They only machines which ever used magnetic sensing for the beginning and
end -of-tape sensing were Beta vcr's.

More often a simple belt driving the counter / sensor ass'y.

Sometimes a mechanical problem, belt, idler, reel lock washer missing, etc.

Rarely something else - a bad lamp, etc. Once in a great while even a Hall
effect sensor ( yes, magnetically actualted. Haven't seen a bad one in at
least fifteen years.)


Mark Z.