Sony cassette recorder motor
John Woodgate
faulty motor speed control transistor. It is totally short-circuit and
badly burned up, but is an NPN (based on the fact that a PNP won't work,
however it's connected!) TO-126 device and the last two digits of the
type number are '94'. The motor is marked 'DNE-4100A', and the supply
voltage is 13.5 V.
I tried several new transistors in place of the fried one, but the motor
terminal voltage seems to be only about 0.5 V less than the input
voltage and the speed is still too high. All the other components (five
resistors, two diodes and two elcos, are OK (measured).
Can anyone please suggest what the type number of the original
transistor might be and/or what the correct motor terminal voltage
should be?
--
Regards, John Woodgate, OOO - Own Opinions Only. Phone +44 (0)1268 747839
Fax +44 (0)1268 777124. http://www.jmwa.demon.co.uk I wanted to make a fully-
automated nuclear-powered trawler,but it went into spontaneous fishing.
PLEASE do not mail copies of newsgroup posts to me.
Gregory Danner
John Woodgate <j...@jmwa.demon.co.uk> wrote:
> I have a Sony TC-FX5C cassette recorder (yes, it's quite old) that
has a
> faulty motor speed control transistor. It is totally short-circuit and
> badly burned up, but is an NPN (based on the fact that a PNP won't
work,
> however it's connected!) TO-126 device and the last two digits of the
> type number are '94'. The motor is marked 'DNE-4100A', and the supply
> voltage is 13.5 V.
>
> I tried several new transistors in place of the fried one, but the
motor
> terminal voltage seems to be only about 0.5 V less than the input
> voltage and the speed is still too high. All the other components
(five
> resistors, two diodes and two elcos, are OK (measured).
>
> Can anyone please suggest what the type number of the original
> transistor might be and/or what the correct motor terminal voltage
> should be?
Many of these internal speed control devices are actually IC chips
rather than transistors. Some of them have four leads, not three.
Sanyo made a lot of them. They aren't readily available as replacement
parts, but you might be able to find a working one in another old motor.
Since cassette deck motors are almost all interchangeable, have you
thought about just putting in a motor from another deck or getting a
replacement one from MCM?
The specs are usually: 12V, CCW (counterclockwise rotation) for home
stereo decks. MCM part# is 28-044, Mabuchi# EG-530AD-2B, $4.99 each.
The new motor may be quite a bit *smaller* than the old one, but
normally has the same bolt hole pattern for attaching it to the chassis
of the cassette transport. You will have to remove the pulley from the
old motor and install it on the new one. Some pulleys have a set
screw, others are just glued or pressed on. Plastic ones can be pulled
off by hand. For pressed-on brass pulleys that DO NOT have a set
screw, heat the pulley with a soldering iron until very hot and then
pull it off with a pair of pliers. A bit of superglue will make this
type of pulley tight on the shaft of the new motor, but be careful not
to let any glue get into the bearing!
One other issue with changing cassette deck motors: In some OEM
motors, the case of the motor is grounded to the negative power input
lead, but in others, it is isolated. All new motors have the case
grounded. If you get audible motor noise in the output of the cassette
deck when playing a tape AFTER putting in a new motor, you may have to
take the new motor back out, pry the back cover off, and remove the
ground connection between the case and negative input terminal. Since
I change a lot of cassette deck motors, I take about half of the batch
when I get new motors, and remove the ground jumpers ahead of time.
Then I just check the old motor for continuity between negative
terminal and case, and use a new motor that is the same (grounded or
isolated).
--
"EB" Greg Danner / Audio-Video Service Center
Sent via Deja.com http://www.deja.com/
Before you buy.
John Woodgate
inimitably wrote:
>Many of these internal speed control devices are actually IC chips
>rather than transistors. Some of them have four leads, not three.
>Sanyo made a lot of them. They aren't readily available as replacement
>parts, but you might be able to find a working one in another old motor.
True, but I am pretty sure this was once a transistor.
>
>Since cassette deck motors are almost all interchangeable, have you
>thought about just putting in a motor from another deck or getting a
>replacement one from MCM?
Thank you very much for your helpful and detailed response. Since I'm in
Britain, I can't easily use the sources you mentioned.
lee.b...@virign.net
John Woodgate wrote:
How similar is the TCFX5 to the TCFX3? I have a used working TCFX3
motor..........
Lee
John Woodgate
>How similar is the TCFX5 to the TCFX3? I have a used working TCFX3
>motor..........
I have no idea. The motor is fitted with a plastic 'barrel' pulley for a
flat belt and the flywheel is massive for a cassette deck. The motor is
fed from a 13.5 V d.c. supply, and the motor itself is mounted between
rubber end-discs inside an outer mild-steel shell lined with what is
probably a mu-metal magnetic screen. The end-cap of the outer shell has
a label marked 'SONY DNE-4100A Made in Japan MMI 6A2LKFB' and what
appears to be a serial number '2871B'.
lee.b...@virign.net
John Woodgate wrote:
The motor from the TCFX3 has part # DNE 4100A, the same as yours :-)
However, I have just tested this motor and whilst it runs fine, the bearings
sound noisy :-(
If you want to take a chance on it for the cost of the postage let me know.
Lee
Gregory Danner
lee.b...@virign.net wrote:
>
> The motor from the TCFX3 has part # DNE 4100A, the same as yours :-)
>
> However, I have just tested this motor and whilst it runs fine, the
bearings
> sound noisy :-(
>
> If you want to take a chance on it for the cost of the postage let me
know.
>
> Lee
>
Most cassette deck (and turntable) motor have fairly loose bearings
that will rattle when operated WITHOUT the belt attached. They usually
quiet down nicely when the belt is on, as it puts enough of a side load
on the bearing to prevent it from rattling.
A good test of a cassette deck motor is the current drain -- it
shouldn't be more than about 50-60 mA for a 12 volt motor when
installed in the deck and playing a tape. Under no load, without the
belt attached, it should be lower, perhaps 30 mA. When the commutator
or brushes fail, they often create a partial short circuit at some
point in the motor's rotation that may create a dead spot or excessive
current drain. Anything over 100 mA is bad.
John Woodgate
inimitably wrote:
>Most cassette deck (and turntable) motor have fairly loose bearings
>that will rattle when operated WITHOUT the belt attached. They usually
>quiet down nicely when the belt is on, as it puts enough of a side load
>on the bearing to prevent it from rattling.
Noted.
>
>A good test of a cassette deck motor is the current drain -- it
>shouldn't be more than about 50-60 mA for a 12 volt motor when
>installed in the deck and playing a tape.
Agreed.
>Under no load, without the
>belt attached, it should be lower, perhaps 30 mA. When the commutator
>or brushes fail, they often create a partial short circuit at some
>point in the motor's rotation that may create a dead spot or excessive
>current drain. Anything over 100 mA is bad.
I found that exactly that is what fried the control transistor. There
was a short-circuit between adjacent commutator segments. Having nothing
to lose, I opened up the motor itself and scraped away the copper dust
causing the short. It was a bit fiddly to get the brushes back on to the
commutator, but the motor still works, and draws about 50 mA. However, I
don't think it will be reliable and the speed control still doesn't
work. The TO-126 device I have substituted for the burnt-up one may have
insufficient current gain - it's a BF457 - all I had in NPN TO-126.
lee.b...@virign.net
Gregory Danner wrote:
> In article <397F2BB5...@virign.net>,
> lee.b...@virign.net wrote:
> >
> > The motor from the TCFX3 has part # DNE 4100A, the same as yours :-)
> >
> > However, I have just tested this motor and whilst it runs fine, the
> bearings
> > sound noisy :-(
> >
> > If you want to take a chance on it for the cost of the postage let me
> know.
> >
> > Lee
> >
>
> Most cassette deck (and turntable) motor have fairly loose bearings
> that will rattle when operated WITHOUT the belt attached. They usually
> quiet down nicely when the belt is on, as it puts enough of a side load
> on the bearing to prevent it from rattling.
>
> A good test of a cassette deck motor is the current drain -- it
> shouldn't be more than about 50-60 mA for a 12 volt motor when
> installed in the deck and playing a tape. Under no load, without the
> belt attached, it should be lower, perhaps 30 mA. When the commutator
> or brushes fail, they often create a partial short circuit at some
> point in the motor's rotation that may create a dead spot or excessive
> current drain. Anything over 100 mA is bad.
>
> --
> "EB" Greg Danner / Audio-Video Service Center
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
This one is 22mA no load and 40-50mA under load.
Lee
Wild Bill
somewhere in the S.E.R. FAQ, which was fabricated from a 3-terminal voltage
regulator and a small pot mounted outside the motor.
It's been quite a while since i saw it, so i'm not really sure it was in the
FAQ.
The original device in these small motors was often a voltage regulator IC,
not a transistor.. which is why the device numbers were difficult to cross
reference.
cheers
WB
..............
John Woodgate wrote in message ...
><8lnkuv$7rt$1...@nnrp1.deja.com>, Gregory Danner <gda...@advancenet.net>
>inimitably wrote:
>>Most cassette deck (and turntable) motor have fairly loose bearings
>>that will rattle when operated WITHOUT the belt attached. They usually
>>quiet down nicely when the belt is on, as it puts enough of a side load
>>on the bearing to prevent it from rattling.
>
>Noted.
>>
>>A good test of a cassette deck motor is the current drain -- it
>>shouldn't be more than about 50-60 mA for a 12 volt motor when
>>installed in the deck and playing a tape.
>
>Agreed.
>>Under no load, without the
>>belt attached, it should be lower, perhaps 30 mA. When the commutator
>>or brushes fail, they often create a partial short circuit at some
>>point in the motor's rotation that may create a dead spot or excessive
>>current drain. Anything over 100 mA is bad.
>
Maarten A.E.Bakker
> <8lnkuv$7rt$1...@nnrp1.deja.com>, Gregory Danner <gda...@advancenet.net>
> was a short-circuit between adjacent commutator segments. Having nothing
> to lose, I opened up the motor itself and scraped away the copper dust
> causing the short. It was a bit fiddly to get the brushes back on to the
> commutator, but the motor still works, and draws about 50 mA. However, I
> don't think it will be reliable and the speed control still doesn't
> work. The TO-126 device I have substituted for the burnt-up one may have
> insufficient current gain - it's a BF457 - all I had in NPN TO-126.
That one will probably burn up, it's a high volt low current type if memory serves me
right. You could try a BD439 or something.
--
Greetings, Maarten.
John Woodgate
for the collector dissipation).
John Woodgate
>If you want to take a chance on it for the cost of the postage let me know.
I took a chance and it worked. The cheque for GBP10 000 is in the post,
Lee. Can I keep the stamp, which I suppose you designed yourself? (;-)
The fried device IS a negative voltage regulator, Matsushita AN6610 (or
AN661Q), similar to an LM337 but in a TO-126 package. This is because it
is enclosed between the PCB and a rubber disc inside the outer housing
of the motor and the opportunity for heat loss is somewhat negligible.
Outside the motor housing an LM337LZ works quite OK. The actual motor
terminal voltage is about 6.5 V. In series with the negative supply is a
0.22 ohm resistor, which is unconventionally colour-coded red, red,
black, silver, so it looks like a 22 ohms 10% tolerance. It should be
red, red, silver = 22 x 0.01. This presumably limits the starting
current from the 13.5 V supply to 600 mA before the motor starts.