Technics RS-TR255 Cassette Decks

[Puddin' Man]

This may well qualify as a "Lost Cause", but ...

I have 2 dual decks per the subject line. On both, the record drive will
not spin a (good, tested) tape. Same tape works OK in the play-only
drive.

On a workbench with the case open, I push button for play or record or
rewind (forward or backward), the machine appears to do a check for
end-of-tape, clicks, and stops.

I disconnected a motor thinking it might be frozen: it was not.

The behavior it exhibits is identical to what the device is supposed
to do when I, say, tell it to play a tape that is pre-positioned to
end-of-tape. I'm guessing that the problem is with the end-of-tape
sensor.

I am neither expert nor helpless with electronics.

Any hope for repairing such a beast?

TIA,
Puddin'

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."

 

[bg]

Puddin' Man wrote in message ...

This may well qualify as a "Lost Cause", but ...

I have 2 dual decks per the subject line. On both, the record drive will
not spin a (good, tested) tape. Same tape works OK in the play-only
drive.

On a workbench with the case open, I push button for play or record or
rewind (forward or backward), the machine appears to do a check for
end-of-tape, clicks, and stops.

I disconnected a motor thinking it might be frozen: it was not.

The behavior it exhibits is identical to what the device is supposed
to do when I, say, tell it to play a tape that is pre-positioned to
end-of-tape. I'm guessing that the problem is with the end-of-tape
sensor.

I am neither expert nor helpless with electronics.

Any hope for repairing such a beast?

TIA,
Puddin'

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."

Usually the take up reel has a sensor to see if it is spinning. The sensor

typically might be a magnetic switch, a simple switch, or an optical sensor.
Sometimes these sensors are driven by belt connected to the take up spool.
There could also be a function built in to activate a stop mode when the
tape counter hits zero. This is so you can rewind back to the same spot on
the tape.

 

[David Nebenzahl]

On 2/17/2010 12:57 PM bg spake thus:

Puddin' Man wrote in message ...

This may well qualify as a "Lost Cause", but ...

I have 2 dual decks per the subject line. On both, the record drive
will not spin a (good, tested) tape. Same tape works OK in the
play-only drive.

On a workbench with the case open, I push button for play or record
or rewind (forward or backward), the machine appears to do a check
for end-of-tape, clicks, and stops.

I disconnected a motor thinking it might be frozen: it was not.

The behavior it exhibits is identical to what the device is
supposed to do when I, say, tell it to play a tape that is
pre-positioned to end-of-tape. I'm guessing that the problem is
with the end-of-tape sensor.

I am neither expert nor helpless with electronics.

Any hope for repairing such a beast?

Usually the take up reel has a sensor to see if it is spinning. The sensor
typically might be a magnetic switch, a simple switch, or an optical sensor.
Sometimes these sensors are driven by belt connected to the take up spool.
There could also be a function built in to activate a stop mode when the
tape counter hits zero. This is so you can rewind back to the same spot on
the tape.

It's also possible that the end-of-tape sensing is done by simply
letting the motor try to spin against the pulleys, and sensing the rise
in current as an end-of-tape condition.

Another possibility is that the drive is simply too weak to spin the
tape, which could be a result of stretched-out belts, dirty drive parts
(belts, pulleys), or (unlikely but possible) stuck bearings somewhere.
If it uses the end-of-tape method described above, it will simply give
up. I'd try to clean up the mechanics first before looking at other causes.


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"

 

[Puddin' Man]

On Wed, 17 Feb 2010 13:19:31 -0800, David Nebenzahl <nobody@but.us.chickens> wrote:

Any hope for repairing such a beast?

Usually the take up reel has a sensor to see if it is spinning. The sensor
typically might be a magnetic switch, a simple switch, or an optical sensor.
Sometimes these sensors are driven by belt connected to the take up spool.
There could also be a function built in to activate a stop mode when the
tape counter hits zero. This is so you can rewind back to the same spot on
the tape.

Thanks ...

I just recalled another detail. The problem drives do auto-reverse.
Been so long since I used 'em I'd forgotten.

It's also possible that the end-of-tape sensing is done by simply
letting the motor try to spin against the pulleys, and sensing the rise
in current as an end-of-tape condition.

Uh-oh. That makes the motor again suspect.

One of the units was on a service contract. The record-drive motor was
replaced in '94. Possibly relevant if the motor is simply of poor quality.

Another possibility is that the drive is simply too weak to spin the
tape, which could be a result of stretched-out belts, dirty drive parts
(belts, pulleys), or (unlikely but possible) stuck bearings somewhere.
If it uses the end-of-tape method described above, it will simply give
up. I'd try to clean up the mechanics first before looking at other causes.

I didn't dissemble much, but what I saw looked pretty clean.

The playback motor has a part # slightly different from that of the
record-drive motor. Safe to assume I could not cannibalize a
playback motor to replace a record-drive motor? A fast search
indicated replacement motors are no longer available.

Danke,
P

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."

 

[Arfa Daily]

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:4b7c5c6a$0$5744$822641b3@news.adtechcomputers.com...

On 2/17/2010 12:57 PM bg spake thus:

Puddin' Man wrote in message ...

This may well qualify as a "Lost Cause", but ...

I have 2 dual decks per the subject line. On both, the record drive
will not spin a (good, tested) tape. Same tape works OK in the
play-only drive.

On a workbench with the case open, I push button for play or record
or rewind (forward or backward), the machine appears to do a check
for end-of-tape, clicks, and stops.

I disconnected a motor thinking it might be frozen: it was not.

The behavior it exhibits is identical to what the device is
supposed to do when I, say, tell it to play a tape that is
pre-positioned to end-of-tape. I'm guessing that the problem is
with the end-of-tape sensor.

I am neither expert nor helpless with electronics.

Any hope for repairing such a beast?

Usually the take up reel has a sensor to see if it is spinning. The
sensor
typically might be a magnetic switch, a simple switch, or an optical
sensor.
Sometimes these sensors are driven by belt connected to the take up
spool.
There could also be a function built in to activate a stop mode when the
tape counter hits zero. This is so you can rewind back to the same spot
on
the tape.

It's also possible that the end-of-tape sensing is done by simply letting
the motor try to spin against the pulleys, and sensing the rise in current
as an end-of-tape condition.

Another possibility is that the drive is simply too weak to spin the tape,
which could be a result of stretched-out belts, dirty drive parts (belts,
pulleys), or (unlikely but possible) stuck bearings somewhere. If it uses
the end-of-tape method described above, it will simply give up. I'd try to
clean up the mechanics first before looking at other causes.


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"

Another common problem is the tape sense switch above the (closed) cassette
holder. It's a simple leaf switch, and it is very common for these to get
'sooty' contacts that *just* make when the door is closed, but then bounce
and un-make momentarily with the vibration of the heads going in or the mech
going into wind / rewind. When the switch un-makes, the system control
thinks that the door has been opened, and immediately drops the deck back to
neutral, and stops it. Easily proved by shorting across the switch from its
terminals at the back, using a screwdriver blade or whatever.

Also, very common for the Technics grey coloured belts to go 'spongy' and
lose their grip.

Arfa

 

[b]

On Feb 17, 7:14 pm, Puddin' Man <puddingDOT...@gmail.com> wrote:

This may well qualify as a "Lost Cause", but ...

I have 2 dual decks per the subject line. On both, the record drive will
not spin a (good, tested) tape. Same tape works OK in the play-only

my TR- 355 has stripped gears on the REC deck take up clutch. Can't
find a service manual or part number, so even if I knew where to get
them, I wouldn't know what to order :-(
might be worth checking these parts on yours -if the mech senses no
take up, it will shut off. But do check the cass-in leaf switches as
Arfa says, I have see this problem numerous times, most recently on
Sony and Panasonic decks.
B
-

 

[William R. Walsh]

Hi!

If it's not engaging in the recording mode, have you checked to be
sure the record prevention safety switch is doing its job?

There should be a small arm that senses whether or not the erase-
protection tabs have been removed from the cassette. If the switch or
optical sensor attached to this arm aren't working, the deck will
refuse to record on a tape.

If it's a switch, you could try shorting across it temporarily and
attempting to engage the recording mode. For a full logic deck like
the one you have, you will need to have a tape in place for it to work
properly--otherwise the tape spill sensor may well shut it down if it
starts in the first place. (Most won't operate without a tape in
place.)

William

 

[David Nebenzahl]

On 2/18/2010 8:30 AM William R. Walsh spake thus:

If it's not engaging in the recording mode, have you checked to be
sure the record prevention safety switch is doing its job?

There should be a small arm that senses whether or not the erase-
protection tabs have been removed from the cassette. If the switch or
optical sensor attached to this arm aren't working, the deck will
refuse to record on a tape.

I don't think that is it: the record-enable switch will (generally, on
every cassette deck I've seen) make it impossible to even engage the
deck in record mode at all. The OP's description seemed to indicate that
the deck would engage when play+record were pressed, but would then
immediately shut off as if at end-of-tape, suggesting some other problem.


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"

 

[Puddin' Man]

On Thu, 18 Feb 2010 12:09:20 -0800, David Nebenzahl <nobody@but.us.chickens> wrote:

On 2/18/2010 8:30 AM William R. Walsh spake thus:

If it's not engaging in the recording mode, have you checked to be
sure the record prevention safety switch is doing its job?

There should be a small arm that senses whether or not the erase-
protection tabs have been removed from the cassette. If the switch or
optical sensor attached to this arm aren't working, the deck will
refuse to record on a tape.

I don't think that is it: the record-enable switch will (generally, on
every cassette deck I've seen) make it impossible to even engage the
deck in record mode at all. The OP's description seemed to indicate that
the deck would engage when play+record were pressed, but would then
immediately shut off as if at end-of-tape, suggesting some other problem.

I just re-tested. Makes no difference whether record is enabled. It
does 2 fast clicks and stops, forward or backward. The 2 clicks
occur slightly faster for backward.

There are a series of contacts just above the cassette. I cleaned
them as best I could with alcohol and Q-tip: made no difference.

Thanks,
P

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."

 

[David Nebenzahl]

On 2/18/2010 12:50 PM Puddin' Man spake thus:

There are a series of contacts just above the cassette. I cleaned
them as best I could with alcohol and Q-tip: made no difference.

I don't think those are contacts; those sound like the springs to hold
the cassette in.


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"

 

[Arfa Daily]

"William R. Walsh" <wm_walsh@hotmail.com> wrote in message
news:4a0db9b3-639b-4155-86c7-35068c40d54c@y17g2000yqd.googlegroups.com...

Hi!

If it's not engaging in the recording mode, have you checked to be
sure the record prevention safety switch is doing its job?

There should be a small arm that senses whether or not the erase-
protection tabs have been removed from the cassette. If the switch or
optical sensor attached to this arm aren't working, the deck will
refuse to record on a tape.

If it's a switch, you could try shorting across it temporarily and
attempting to engage the recording mode. For a full logic deck like
the one you have, you will need to have a tape in place for it to work
properly--otherwise the tape spill sensor may well shut it down if it
starts in the first place. (Most won't operate without a tape in
place.)

William

I think that he is more referring to the deck by function to identify which
one he is talking about in case it makes a difference to the diagnosis,
rather than talking about the problem being specifically record-associated.

i.e. the unit has two decks, one of which is a record / play deck (the one
the OP is referring to) and the other being play only. This is a common
arrangement on dual deck machines, as there is no valid case for having both
decks capable of recording.

Arfa

 

[Arfa Daily]

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:4b7dcf5d$0$3261$822641b3@news.adtechcomputers.com...

On 2/18/2010 12:50 PM Puddin' Man spake thus:

There are a series of contacts just above the cassette. I cleaned
them as best I could with alcohol and Q-tip: made no difference.

I don't think those are contacts; those sound like the springs to hold the
cassette in.


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"

There usually are several sets of contacts, one of which is the cassette
sense switch, the others being for sensing the record prevention tab (at
left side), and auto tape-type detection (right centre). Are you sure that
you actually got to the contacts ? These leaf switches normally have a clear
plastic cover over them, and it is necessary to remove this to clean them
successfully. This often involves withdrawing the pcb that they are soldered
to. When you can genuinely get to the contacts, they are best cleaned by
drawing a piece of paper soaked in switch cleaner through them, whilst
keeping some tension squeezed on them.

Another place that you might look is on the main body of the deck. I can't
remember if Technics decks have this additional switch or not, but many
decks do. It is another leaf switch, but usually an open type, and somewhat
smaller than the cassette sense switches. It is operated by the top edge of
the head plate pressing on it as the heads go fully in, to inform the system
control micro that the loading sequence has completed. These switches often
go intermittent like the sense switches, and again give the same symptom of
the deck going through the loading sequence, then dropping back to neutral
before the tape starts to transport.

Arfa

 

On Fri, 19 Feb 2010 02:04:27 -0000, "Arfa Daily"
<arfa.daily@ntlworld.com>wrote:

"William R. Walsh" <wm_walsh@hotmail.com> wrote in message
news:4a0db9b3-639b-4155-86c7-35068c40d54c@y17g2000yqd.googlegroups.com...
Hi!

If it's not engaging in the recording mode, have you checked to be
sure the record prevention safety switch is doing its job?

There should be a small arm that senses whether or not the erase-
protection tabs have been removed from the cassette. If the switch or
optical sensor attached to this arm aren't working, the deck will
refuse to record on a tape.

If it's a switch, you could try shorting across it temporarily and
attempting to engage the recording mode. For a full logic deck like
the one you have, you will need to have a tape in place for it to work
properly--otherwise the tape spill sensor may well shut it down if it
starts in the first place. (Most won't operate without a tape in
place.)

William

I think that he is more referring to the deck by function to identify which
one he is talking about in case it makes a difference to the diagnosis,
rather than talking about the problem being specifically record-associated.

i.e. the unit has two decks, one of which is a record / play deck (the one
the OP is referring to) and the other being play only. This is a common
arrangement on dual deck machines, as there is no valid case for having both
decks capable of recording.

Arfa

I own a pretty high end Sony dual and only deck B records. I don't
recall one that records on both like you mention there is no need.

 

[Arfa Daily]

<Meat Plow> wrote in message news:3hiriq.mrv.19.6@news.alt.net...

On Fri, 19 Feb 2010 02:04:27 -0000, "Arfa Daily"
arfa.daily@ntlworld.com>wrote:


"William R. Walsh" <wm_walsh@hotmail.com> wrote in message
news:4a0db9b3-639b-4155-86c7-35068c40d54c@y17g2000yqd.googlegroups.com...
Hi!

If it's not engaging in the recording mode, have you checked to be
sure the record prevention safety switch is doing its job?

There should be a small arm that senses whether or not the erase-
protection tabs have been removed from the cassette. If the switch or
optical sensor attached to this arm aren't working, the deck will
refuse to record on a tape.

If it's a switch, you could try shorting across it temporarily and
attempting to engage the recording mode. For a full logic deck like
the one you have, you will need to have a tape in place for it to work
properly--otherwise the tape spill sensor may well shut it down if it
starts in the first place. (Most won't operate without a tape in
place.)

William

I think that he is more referring to the deck by function to identify
which
one he is talking about in case it makes a difference to the diagnosis,
rather than talking about the problem being specifically
record-associated.

i.e. the unit has two decks, one of which is a record / play deck (the one
the OP is referring to) and the other being play only. This is a common
arrangement on dual deck machines, as there is no valid case for having
both
decks capable of recording.

Arfa


I own a pretty high end Sony dual and only deck B records. I don't
recall one that records on both like you mention there is no need.

Quite so.

Arfa

 

[Puddin' Man]

Much thanks for numerous responses.

It looks like I'll have to attempt to dissemble a dysfunctional drive.
Without schematic or other doc.

Other bonfires have taken precedence. I dunno when I'll be able to get
back to the "Lazarus-From-The-Dead" cassette project.

But your help was much appreciated, and, with luck, may yet provide
the needed guidance.

Cheers,
P

On Wed, 17 Feb 2010 12:14:08 -0600, Puddin' Man <puddingDOTman@gmail.com> wrote:

This may well qualify as a "Lost Cause", but ...

I have 2 dual decks per the subject line. On both, the record drive will
not spin a (good, tested) tape. Same tape works OK in the play-only
drive.

On a workbench with the case open, I push button for play or record or
rewind (forward or backward), the machine appears to do a check for
end-of-tape, clicks, and stops.

I disconnected a motor thinking it might be frozen: it was not.

The behavior it exhibits is identical to what the device is supposed
to do when I, say, tell it to play a tape that is pre-positioned to
end-of-tape. I'm guessing that the problem is with the end-of-tape
sensor.

I am neither expert nor helpless with electronics.

Any hope for repairing such a beast?

TIA,
Puddin'

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."