According to the internet a respected deck in its day.
Had to deal with the slip clutch buried in the mechanism. Photoed before
disassembly just in case. Reassembled and the 2 pinch wheels were fighting
one another. A strange pair of springs one acting against the other for the
"reverse" pinch wheel assembly. I must have put one of these springs back
with wrong anchor position. Correcting that and its playing and FF and REW
ok.
These units are called 4 head, 4 pairs of screened stereo wires going to the
head but all seem to relate half the tape. So one question is why 2 pinch
wheels when there seems to be no proper "reverse" side play or loop control
function as a fixed head.
Repeat sends back to replay the same side.
The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the pinchwheel
and into the recess of the cassette - what is the function of that
protrusion and a non pinching pinch wheel ?
What do the 4 stereo heads do ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N Cook" wrote in message
...
According to the internet a respected deck in its day.
Had to deal with the slip clutch buried in the mechanism. Photoed before
disassembly just in case. Reassembled and the 2 pinch wheels were fighting
one another. A strange pair of springs one acting against the other for
the
"reverse" pinch wheel assembly. I must have put one of these springs back
with wrong anchor position. Correcting that and its playing and FF and
REW
ok.
These units are called 4 head, 4 pairs of screened stereo wires going to
the
head but all seem to relate half the tape. So one question is why 2 pinch
wheels when there seems to be no proper "reverse" side play or loop
control
function as a fixed head.
Repeat sends back to replay the same side.
The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the
pinchwheel
and into the recess of the cassette - what is the function of that
protrusion and a non pinching pinch wheel ?
What do the 4 stereo heads do ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




I think its an ADF 770. Could it be a 3 head model?

one that can replay the tape while it is being recorded ?

Dave wrote in message
. uk...

"N Cook" wrote in message
...
According to the internet a respected deck in its day.
Had to deal with the slip clutch buried in the mechanism. Photoed before
disassembly just in case. Reassembled and the 2 pinch wheels were
fighting
one another. A strange pair of springs one acting against the other for
the
"reverse" pinch wheel assembly. I must have put one of these springs
back
with wrong anchor position. Correcting that and its playing and FF and
REW
ok.
These units are called 4 head, 4 pairs of screened stereo wires going to
the
head but all seem to relate half the tape. So one question is why 2
pinch
wheels when there seems to be no proper "reverse" side play or loop
control
function as a fixed head.
Repeat sends back to replay the same side.
The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the
pinchwheel
and into the recess of the cassette - what is the function of that
protrusion and a non pinching pinch wheel ?
What do the 4 stereo heads do ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




I think its an ADF 770. Could it be a 3 head model?

one that can replay the tape while it is being recorded ?



Yes F770 on the front and AD F770 on the back.
Yes 3 head , presumably one erase head and one double head, 2 motors.
why would someone need to replay at record - some semi-pro facility for EQ
checks ?

On 6 Mar, 16:19, "N Cook" wrote:

These units are called 4 head, 4 pairs of screened stereo wires going to the
head but all seem to relate half the tape. So one question is why 2 pinch
wheels when there seems to be no proper "reverse" side play or loop control
function as a fixed head.

The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the pinchwheel
and into the recess of the cassette - what is the function of that
protrusion and a non pinching pinch wheel ?

What do the 4 stereo heads do ?

why would someone need to replay at record - some semi-pro facility for EQ
checks ?

Sounds like a quality cassette deck.

2 pinchwheels are used to pull the tape taut as it passes over the
heads. The reuslt is a dramatic increase in reliability of tape to
head contact, thus eliminating a common cause of poor quality sound.

4 heads are used so that one can listen to the played back signal
during recording. This enables several things:
1. you can adjust the bias and hear the result almost instantly,
which makes a quality improvement with many tapes
2. If there is muck on the head, a bad tape, incomplete erase, or any
other recording problem, you know immediately, and dont waste a lot of
time making a dud recording.

Sounds like its well worth fixing.

As for the pinchwheel protrusion, I dont know what it looks like so
its impossible to say. Peraps its a small protrusion designed to hold
the cassette in exactly the right position, cheaper decks often dont
have accurate cassette shell holding, with predictable inconsistent
results on tape to head contact and alignment.

PS all this technology goes back to the 70s, there was a late 70s
Pioneer that had all the above, and is/was still one of the best
cassetts decks 20 years later.


NT

"N Cook" wrote in :

According to the internet a respected deck in its day.
Had to deal with the slip clutch buried in the mechanism. Photoed before
disassembly just in case. Reassembled and the 2 pinch wheels were
fighting one another. A strange pair of springs one acting against the
other for the "reverse" pinch wheel assembly. I must have put one of
these springs back with wrong anchor position. Correcting that and its
playing and FF and REW ok.
These units are called 4 head, 4 pairs of screened stereo wires going to
the head but all seem to relate half the tape. So one question is why 2
pinch wheels when there seems to be no proper "reverse" side play or
loop control function as a fixed head.
Repeat sends back to replay the same side.
The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the
pinchwheel and into the recess of the cassette - what is the function of
that protrusion and a non pinching pinch wheel ?
What do the 4 stereo heads do ?


Could it be an auto reverse deck that reverses when it hits a metal band or
transparent area of the tape, near the end of the reel?

One set of heads plays/records in one direction and the other set
plays/records in the other direction?

I seem to remember Aiwa had some like that.
My shop used to work on them in the early 70's (back when I had a shop).

The strange guide could be a 'tape tension' sensor. It may have been
disabled at some time in the past to fix some problem.

Google shows several "Aiwa F770 Three-Head Studio Quality Cassette Deck"
listings, so the chances are that it is to allow 'sound over' recording by
playing back and mixing in new audio and then recording that, after the
sound that was just played is erased.

One last possiblity, the second pinch roller could be for a second
recording speed. I seem to remember some machines that played that trick to
allow multi speed recording.






--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

"N Cook" wrote in :

Yes F770 on the front and AD F770 on the back.
Yes 3 head , presumably one erase head and one double head, 2 motors.
why would someone need to replay at record - some semi-pro facility for EQ
checks ?




not replay at record. Get the sound currently on the tape off, mix it with
some new sound and re-record it.

Les Paul and Mary Ford used to do multi part harmony with just two singers
and two guitars by such a method.





--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

bz wrote:

"N Cook" wrote in :

Yes F770 on the front and AD F770 on the back.
Yes 3 head , presumably one erase head and one double head, 2 motors.
why would someone need to replay at record - some semi-pro facility for EQ
checks ?




not replay at record. Get the sound currently on the tape off, mix it with
some new sound and re-record it.

Les Paul and Mary Ford used to do multi part harmony with just two singers
and two guitars by such a method.

--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

When you get to this era - not necessarily. If the deck had any bias
adjustment control then you needed a three head setup to compare the
sound coming off the tape to the source in order to tweak the bias
setting to an optimum position for the tape being used. Funny that my
TEAC V770 has this option and the model number is so similar to the Awia
unit here.

Rick

N Cook wrote:
why would someone need to replay at record - some semi-pro facility for EQ
checks ?

That was an expensive and desirable feature. You knew immediately if there
were problems, such as badly set record gain, dirty heads, tape path
problems, etc. etc. Anyone who's ever made an important recording and
found out at playback time it didn't work would give his auto-reverse
for this feature.

--
Martians drive SUVs! http://oregonmag.com/MarsWarm307.html

wrote in message
oups.com...
On 6 Mar, 16:19, "N Cook" wrote:

These units are called 4 head, 4 pairs of screened stereo wires going to
the
head but all seem to relate half the tape. So one question is why 2
pinch
wheels when there seems to be no proper "reverse" side play or loop
control
function as a fixed head.

The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the
pinchwheel
and into the recess of the cassette - what is the function of that
protrusion and a non pinching pinch wheel ?

What do the 4 stereo heads do ?

why would someone need to replay at record - some semi-pro facility for
EQ
checks ?

Sounds like a quality cassette deck.

2 pinchwheels are used to pull the tape taut as it passes over the
heads. The reuslt is a dramatic increase in reliability of tape to
head contact, thus eliminating a common cause of poor quality sound.

4 heads are used so that one can listen to the played back signal
during recording. This enables several things:
1. you can adjust the bias and hear the result almost instantly,
which makes a quality improvement with many tapes
2. If there is muck on the head, a bad tape, incomplete erase, or any
other recording problem, you know immediately, and dont waste a lot of
time making a dud recording.

Sounds like its well worth fixing.

As for the pinchwheel protrusion, I dont know what it looks like so
its impossible to say. Peraps its a small protrusion designed to hold
the cassette in exactly the right position, cheaper decks often dont
have accurate cassette shell holding, with predictable inconsistent
results on tape to head contact and alignment.

PS all this technology goes back to the 70s, there was a late 70s
Pioneer that had all the above, and is/was still one of the best
cassetts decks 20 years later.


NT


That explains the multiple heads, the protruding tape guide and the free
running "pinch wheel" but why a contra-rotating spindle adjascent to it if
its not used for any reverse play / review function or any function that i
can see ?

bz wrote in message
98.139...
"N Cook" wrote in :

According to the internet a respected deck in its day.
Had to deal with the slip clutch buried in the mechanism. Photoed before
disassembly just in case. Reassembled and the 2 pinch wheels were
fighting one another. A strange pair of springs one acting against the
other for the "reverse" pinch wheel assembly. I must have put one of
these springs back with wrong anchor position. Correcting that and its
playing and FF and REW ok.
These units are called 4 head, 4 pairs of screened stereo wires going to
the head but all seem to relate half the tape. So one question is why 2
pinch wheels when there seems to be no proper "reverse" side play or
loop control function as a fixed head.
Repeat sends back to replay the same side.
The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the
pinchwheel and into the recess of the cassette - what is the function of
that protrusion and a non pinching pinch wheel ?
What do the 4 stereo heads do ?


Could it be an auto reverse deck that reverses when it hits a metal band
or
transparent area of the tape, near the end of the reel?

One set of heads plays/records in one direction and the other set
plays/records in the other direction?

I seem to remember Aiwa had some like that.
My shop used to work on them in the early 70's (back when I had a shop).

The strange guide could be a 'tape tension' sensor. It may have been
disabled at some time in the past to fix some problem.

Google shows several "Aiwa F770 Three-Head Studio Quality Cassette Deck"
listings, so the chances are that it is to allow 'sound over' recording by
playing back and mixing in new audio and then recording that, after the
sound that was just played is erased.

One last possiblity, the second pinch roller could be for a second
recording speed. I seem to remember some machines that played that trick
to
allow multi speed recording.






--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

The 2 pinch wheel holders are engaged/disengaged by the same sliding plate
so the normal one is engaged against the spindle and the "reverse" one is
close to the contra rotating spindle. There is no possibility of the sliding
plate to do anything else eg swivel to engage one
or the other fully.

The added tape guide is part of the normal swinging mount of a pinch wheel
but extending around a part of the curve of the pinch wheel so intruding
into the tape path.

I'll take some pics tomorrow and upload somewhere.

bz wrote in message
98.139...
"N Cook" wrote in :

According to the internet a respected deck in its day.
Had to deal with the slip clutch buried in the mechanism. Photoed before
disassembly just in case. Reassembled and the 2 pinch wheels were
fighting one another. A strange pair of springs one acting against the
other for the "reverse" pinch wheel assembly. I must have put one of
these springs back with wrong anchor position. Correcting that and its
playing and FF and REW ok.
These units are called 4 head, 4 pairs of screened stereo wires going to
the head but all seem to relate half the tape. So one question is why 2
pinch wheels when there seems to be no proper "reverse" side play or
loop control function as a fixed head.
Repeat sends back to replay the same side.
The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the
pinchwheel and into the recess of the cassette - what is the function of
that protrusion and a non pinching pinch wheel ?
What do the 4 stereo heads do ?


Could it be an auto reverse deck that reverses when it hits a metal band
or
transparent area of the tape, near the end of the reel?

One set of heads plays/records in one direction and the other set
plays/records in the other direction?

I seem to remember Aiwa had some like that.
My shop used to work on them in the early 70's (back when I had a shop).

The strange guide could be a 'tape tension' sensor. It may have been
disabled at some time in the past to fix some problem.

Google shows several "Aiwa F770 Three-Head Studio Quality Cassette Deck"
listings, so the chances are that it is to allow 'sound over' recording by
playing back and mixing in new audio and then recording that, after the
sound that was just played is erased.

One last possiblity, the second pinch roller could be for a second
recording speed. I seem to remember some machines that played that trick
to
allow multi speed recording.






--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap


picture with the odd pinch wheel housing on the left, normal one to the
right

http://home.graffiti.net/diverse:graffiti.net/aiwa2.jpg
or
http://home.graffiti.net/diverse:graffiti.net/aiwa.htm


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N Cook" wrote in :

picture with the odd pinch wheel housing on the left, normal one to the
right

http://home.graffiti.net/diverse:graffiti.net/aiwa2.jpg
or
http://home.graffiti.net/diverse:graffiti.net/aiwa.htm


Looks like the head has two sets of stereo heads, offset from each other

-
-
-
-

Which would support the two way supposition.




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

bz ha escrito:
"N Cook" wrote in :

picture with the odd pinch wheel housing on the left, normal one to the
right

http://home.graffiti.net/diverse:graffiti.net/aiwa2.jpg
or
http://home.graffiti.net/diverse:graffiti.net/aiwa.htm

What you have here is a single direction, 3 head tape deck. The
capstans should both go the same way. If not, you have a capstan belt
on incorrectly. Try it.

BTW, the protrusion on the LH pinch roller is a tape guide to ensure
the tape is fed to the pinch/capstan perfectly straight. In some
models of more elaborate decks which had both 3 heads AND
autoreverse, I'm sure i recall having seen it used as the erase head!

-Ben.

b wrote in message
ps.com...

bz ha escrito:
"N Cook" wrote in
:

picture with the odd pinch wheel housing on the left, normal one to
the
right

http://home.graffiti.net/diverse:graffiti.net/aiwa2.jpg
or
http://home.graffiti.net/diverse:graffiti.net/aiwa.htm

What you have here is a single direction, 3 head tape deck. The
capstans should both go the same way. If not, you have a capstan belt
on incorrectly. Try it.

BTW, the protrusion on the LH pinch roller is a tape guide to ensure
the tape is fed to the pinch/capstan perfectly straight. In some
models of more elaborate decks which had both 3 heads AND
autoreverse, I'm sure i recall having seen it used as the erase head!

-Ben.


I had assumed the low-side wow, when i had the springs set wrong, was due to
one pinch wheel fighting the other. Perhaps that black plastic tape guide
was touching the spindle and breaking the whole train , then.
Both capstans in fact do rotate the same way.
Surely you can't have 2 flywheels and 2 capstans with pinchwheels engaging
the same tape, even if connected by the same rubber band.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

On 7 Mar, 08:32, "N Cook" wrote:
b wrote in message
ps.com...
bz ha escrito:
"N Cook" wrote in
:

http://home.graffiti.net/diverse:graffiti.net/aiwa2.jpg
or
http://home.graffiti.net/diverse:graffiti.net/aiwa.htm

the extra bit is a tape guide for better tape path control.


What you have here is a single direction, 3 head tape deck. The
capstans should both go the same way. If not, you have a capstan belt
on incorrectly. Try it.

absolutely, they must rotate same way


Surely you can't have 2 flywheels and 2 capstans with pinchwheels engaging
the same tape, even if connected by the same rubber band.

Yes, thats how they work. The one on the left is driven by the one on
the right via a belt. Belts are a little lossy since they stretch at
one end more than the other, giving a slight speed difference when
free running. Put the tape in and this translates to putting tension
on the tape. Its a very effective method. Once you've had a deck like
this you wont want to go back to the cheaper more common system.


NT

wrote in message
oups.com...
On 7 Mar, 08:32, "N Cook" wrote:
b wrote in message
ps.com...
bz ha escrito:
"N Cook" wrote in
:

http://home.graffiti.net/diverse:graffiti.net/aiwa2.jpg
or
http://home.graffiti.net/diverse:graffiti.net/aiwa.htm

the extra bit is a tape guide for better tape path control.


What you have here is a single direction, 3 head tape deck. The
capstans should both go the same way. If not, you have a capstan belt
on incorrectly. Try it.

absolutely, they must rotate same way


Surely you can't have 2 flywheels and 2 capstans with pinchwheels
engaging
the same tape, even if connected by the same rubber band.

Yes, thats how they work. The one on the left is driven by the one on
the right via a belt. Belts are a little lossy since they stretch at
one end more than the other, giving a slight speed difference when
free running. Put the tape in and this translates to putting tension
on the tape. Its a very effective method. Once you've had a deck like
this you wont want to go back to the cheaper more common system.


NT


I put the deck back in the chassis to check speed and record function.
If I had not been aware of the features before that i would certainly now on
record.
It routinely uses playback at record as VU and PPM rather than direct from
source. So you set to record a signal and nothing appears on the VUs until
the tape has passed from leader to ferrite.
Nice to have big numbers etc on a proper large clear and bright cold cathode
display.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

On 7 Mar, 11:24, "N Cook" wrote:

I put the deck back in the chassis to check speed and record function.
If I had not been aware of the features before that i would certainly now on
record.
It routinely uses playback at record as VU and PPM rather than direct from
source. So you set to record a signal and nothing appears on the VUs until
the tape has passed from leader to ferrite.
Nice to have big numbers etc on a proper large clear and bright cold cathode
display.

I dont know the Aiwa one, but typically on this type of deck you can
switch metering and audio output between record head and play head, so
you can run it either way.


NT

wrote:

I dont know the Aiwa one, but typically on this type of deck you can
switch metering and audio output between record head and play head, so
you can run it either way.

'Tape-source' switch, usually.
-B.

N Cook wrote in message
...
wrote in message
oups.com...
On 7 Mar, 08:32, "N Cook" wrote:
b wrote in message
ps.com...
bz ha escrito:
"N Cook" wrote in
:

http://home.graffiti.net/diverse:graffiti.net/aiwa2.jpg
or
http://home.graffiti.net/diverse:graffiti.net/aiwa.htm

the extra bit is a tape guide for better tape path control.


What you have here is a single direction, 3 head tape deck. The
capstans should both go the same way. If not, you have a capstan
belt
on incorrectly. Try it.

absolutely, they must rotate same way


Surely you can't have 2 flywheels and 2 capstans with pinchwheels
engaging
the same tape, even if connected by the same rubber band.

Yes, thats how they work. The one on the left is driven by the one on
the right via a belt. Belts are a little lossy since they stretch at
one end more than the other, giving a slight speed difference when
free running. Put the tape in and this translates to putting tension
on the tape. Its a very effective method. Once you've had a deck like
this you wont want to go back to the cheaper more common system.


NT


I put the deck back in the chassis to check speed and record function.
If I had not been aware of the features before that i would certainly now
on
record.
It routinely uses playback at record as VU and PPM rather than direct from
source. So you set to record a signal and nothing appears on the VUs until
the tape has passed from leader to ferrite.
Nice to have big numbers etc on a proper large clear and bright cold
cathode
display.




Back to the original problem.
The belts had dropped off, obviously perished.
Now , sometimes, on using the power take off to slide up the head carrier
one of the belts drops off. The one that links the 2 flywheels directly
together. The first motor to flywheel belt stays on.
The second belt is driven by a flat pulley driving a vaguely bulbous pulley.
Belt dimensins of width and thickness are much the same as the originals but
obviously the length is less than the perished one - try a longer belt ?
There may be just enough room to add a disc of plastic to the flywheel to
stop it falling off or putting a static guard in place - any ideas?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook ha escrito:
Back to the original problem.
The belts had dropped off, obviously perished.
Now , sometimes, on using the power take off to slide up the head carrier
one of the belts drops off. The one that links the 2 flywheels directly
together. The first motor to flywheel belt stays on.
The second belt is driven by a flat pulley driving a vaguely bulbous pulley.
Belt dimensins of width and thickness are much the same as the originals but
obviously the length is less than the perished one - try a longer belt ?
There may be just enough room to add a disc of plastic to the flywheel to
stop it falling off or putting a static guard in place - any ideas?

I don't understand. have you replaced the belts with new? if so,
nothing should be falling off and nothing will need modifying.

-B.

b wrote in message
oups.com...

N Cook ha escrito:
Back to the original problem.
The belts had dropped off, obviously perished.
Now , sometimes, on using the power take off to slide up the head
carrier
one of the belts drops off. The one that links the 2 flywheels directly
together. The first motor to flywheel belt stays on.
The second belt is driven by a flat pulley driving a vaguely bulbous
pulley.
Belt dimensins of width and thickness are much the same as the originals
but
obviously the length is less than the perished one - try a longer belt ?
There may be just enough room to add a disc of plastic to the flywheel
to
stop it falling off or putting a static guard in place - any ideas?

I don't understand. have you replaced the belts with new? if so,
nothing should be falling off and nothing will need modifying.

-B.


both new bands and cleaned pulleys. moving from REW to play causes the band
to fall off, presumably due to a snatching / breaking / imbalance associated
with this double connection to the tape presumably at take up.
If I put in a guide then it can't fall off and will presumably self centre
back up the vague hump on the periphery of the "reverse" flywheel.
On baluster/ bulbous motor pulleys they usually have a preventer disc either
side of the bulging active part. This pulley has a larger pulley on one side
but nothing on the other in the way of a preventer.

N Cook ha escrito:
b wrote in message
oups.com...

N Cook ha escrito:
Back to the original problem.
The belts had dropped off, obviously perished.
Now , sometimes, on using the power take off to slide up the head


both new bands and cleaned pulleys. moving from REW to play causes the band
to fall off, presumably due to a snatching / breaking / imbalance associated
with this double connection to the tape presumably at take up.
If I put in a guide then it can't fall off and will presumably self centre
back up the vague hump on the periphery of the "reverse" flywheel.
On baluster/ bulbous motor pulleys they usually have a preventer disc either
side of the bulging active part. This pulley has a larger pulley on one side
but nothing on the other in the way of a preventer.

Hmmm....if thers no sign of there having being a preventer in the
past, i'd be inclined to think that the belt is not the correct
replacement - too slack?? It should be albe to withstand the change
of tension without slipping or wandering.
-B.

b wrote in message
oups.com...

N Cook ha escrito:
b wrote in message
oups.com...

N Cook ha escrito:
Back to the original problem.
The belts had dropped off, obviously perished.
Now , sometimes, on using the power take off to slide up the head


both new bands and cleaned pulleys. moving from REW to play causes the
band
to fall off, presumably due to a snatching / breaking / imbalance
associated
with this double connection to the tape presumably at take up.
If I put in a guide then it can't fall off and will presumably self
centre
back up the vague hump on the periphery of the "reverse" flywheel.
On baluster/ bulbous motor pulleys they usually have a preventer disc
either
side of the bulging active part. This pulley has a larger pulley on one
side
but nothing on the other in the way of a preventer.

Hmmm....if thers no sign of there having being a preventer in the
past, i'd be inclined to think that the belt is not the correct
replacement - too slack?? It should be albe to withstand the change
of tension without slipping or wandering.
-B.


No signs of any preventers removed.
I think its the other way round. The one I replaced it with was a bit too
short/tight as you would normally do, it is probably highly critical. The
problem point is at moment of power switch on so the trailing pulley is
static, so inertial slack in the belt . The force in the belt to pull it
down the vague hump is higher than the differential force at the hump to
push it to the maximum part of the hump it would seem. If it rides down
initially to the axial paired larger pulley then no trouble but if it goes
the other way it falls off.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:
b wrote in message
oups.com...
N Cook ha escrito:
b wrote in message
oups.com...
N Cook ha escrito:
Back to the original problem.
The belts had dropped off, obviously perished.
Now , sometimes, on using the power take off to slide up the head

both new bands and cleaned pulleys. moving from REW to play causes the
band
to fall off, presumably due to a snatching / breaking / imbalance
associated
with this double connection to the tape presumably at take up.
If I put in a guide then it can't fall off and will presumably self
centre
back up the vague hump on the periphery of the "reverse" flywheel.
On baluster/ bulbous motor pulleys they usually have a preventer disc
either
side of the bulging active part. This pulley has a larger pulley on one
side
but nothing on the other in the way of a preventer.
Hmmm....if thers no sign of there having being a preventer in the
past, i'd be inclined to think that the belt is not the correct
replacement - too slack?? It should be albe to withstand the change
of tension without slipping or wandering.
-B.


No signs of any preventers removed.
I think its the other way round. The one I replaced it with was a bit too
short/tight as you would normally do, it is probably highly critical. The
problem point is at moment of power switch on so the trailing pulley is
static, so inertial slack in the belt . The force in the belt to pull it
down the vague hump is higher than the differential force at the hump to
push it to the maximum part of the hump it would seem. If it rides down
initially to the axial paired larger pulley then no trouble but if it goes
the other way it falls off.


Have you checked for slight wear in the bearing of the shaft with the
barrel shaped pulley? Is the new belt the same width as the old one?

Ron(UK)

N Cook wrote:
b wrote in message
oups.com...
N Cook ha escrito:

Back to the original problem.
The belts had dropped off, obviously perished.
Now , sometimes, on using the power take off to slide up the head
carrier
one of the belts drops off. The one that links the 2 flywheels directly
together. The first motor to flywheel belt stays on.
The second belt is driven by a flat pulley driving a vaguely bulbous
pulley.
Belt dimensins of width and thickness are much the same as the originals
but
obviously the length is less than the perished one - try a longer belt ?
There may be just enough room to add a disc of plastic to the flywheel
to
stop it falling off or putting a static guard in place - any ideas?

I don't understand. have you replaced the belts with new? if so,
nothing should be falling off and nothing will need modifying.

-B.


both new bands and cleaned pulleys. moving from REW to play causes the band
to fall off, presumably due to a snatching / breaking / imbalance associated
with this double connection to the tape presumably at take up.
If I put in a guide then it can't fall off and will presumably self centre
back up the vague hump on the periphery of the "reverse" flywheel.
On baluster/ bulbous motor pulleys they usually have a preventer disc either
side of the bulging active part. This pulley has a larger pulley on one side
but nothing on the other in the way of a preventer.

I've come across this one occasionally, and have fixed it by adding a
fixed guard each side, not by the drivewheel but beside the belt close
to where it goes onto the wheel. That way the belt momentarily
impacting the guard does not cause problems, and steers it properly on
the wheel.

I dont know why or how this can happen, but the fix works.


NT