Before I tear this thing apart, I thought I'd "go to the well" to see if
anyone has had the same problem.

I acquired an exceptional SB-301, but the tuning range is restricted.

The LMO is supposed to tune 500 KC - from X.0 to X.5. Mine physically stops
at X.055 ... in other words, the counterclockwise "end of travel thunk"
comes too early, and won't let me tune the bottom 55 kc of the band. The
clockwise "end of travel thunk" comes where it should. These "thunks" both
sound and feel the same .... as you would expect them to: solid and
defined, neither end like the feel / sound of a coil getting caught up
inside a tube. The tuning is smooth and unobstructed across the full range.

All told, I get around 432 kc of mechanical travel instead of 500 kc.

The LMO output is supposed to be from 5.0 to 5.5 Mhz. Mine ranges from
appx. 5.014 to 5.444 Mhz.

The readout is correct - a signal transmitted on 7.2 Mhz. is received on 7.2
Mhz per the dial.

The construction of this receiver is about the best I have ever seen on an
SB-XXX kit, so I don't think it's a question of shoddy craftsmanship.
Visual review of the mounting of the LMO, dial, knob, shaft, and 100KC
insert into the spiral on the back of the tuning dial all seems to be
perfect, with no obstructions showing anywhere.

So, that's what I'm looking at ... essentially a perfect LMO, but with
abbreviated end-to-end travel.

My hope is that I'm just missing something stupid, and it is pointed out to
me so I don't completely disassemble the unit if I don't have to.

Thanks in advance for the input.

73,
Jeff
W8KZW

If I remember right there are several "dogs" on the shaft that control
how many turns the pto shaft can make. If they are not installed
properly it will limit the revolutions. They are right next to the pto
housing on the shaft on the outside. Unless I am getting mixed up with
the collins pto's. About a half dozen or so washer like with a bent
tab on each.

73
Gary K4FMX

On Mon, 7 Mar 2005 08:23:17 -0500, "W8KZW" wrote:

Before I tear this thing apart, I thought I'd "go to the well" to see if
anyone has had the same problem.

I acquired an exceptional SB-301, but the tuning range is restricted.

The LMO is supposed to tune 500 KC - from X.0 to X.5. Mine physically stops
at X.055 ... in other words, the counterclockwise "end of travel thunk"
comes too early, and won't let me tune the bottom 55 kc of the band. The
clockwise "end of travel thunk" comes where it should. These "thunks" both
sound and feel the same .... as you would expect them to: solid and
defined, neither end like the feel / sound of a coil getting caught up
inside a tube. The tuning is smooth and unobstructed across the full range.

All told, I get around 432 kc of mechanical travel instead of 500 kc.

The LMO output is supposed to be from 5.0 to 5.5 Mhz. Mine ranges from
appx. 5.014 to 5.444 Mhz.

The readout is correct - a signal transmitted on 7.2 Mhz. is received on 7.2
Mhz per the dial.

The construction of this receiver is about the best I have ever seen on an
SB-XXX kit, so I don't think it's a question of shoddy craftsmanship.
Visual review of the mounting of the LMO, dial, knob, shaft, and 100KC
insert into the spiral on the back of the tuning dial all seems to be
perfect, with no obstructions showing anywhere.

So, that's what I'm looking at ... essentially a perfect LMO, but with
abbreviated end-to-end travel.

My hope is that I'm just missing something stupid, and it is pointed out to
me so I don't completely disassemble the unit if I don't have to.

Thanks in advance for the input.

73,
Jeff
W8KZW

W8KZW wrote:
Before I tear this thing apart, I thought I'd "go to the well" to see
if
anyone has had the same problem.

I acquired an exceptional SB-301, but the tuning range is restricted.

The LMO is supposed to tune 500 KC - from X.0 to X.5. Mine
physically stops
at X.055 ... in other words, the counterclockwise "end of travel
thunk"
comes too early, and won't let me tune the bottom 55 kc of the band.
The
clockwise "end of travel thunk" comes where it should. These
"thunks" both
sound and feel the same .... as you would expect them to: solid and
defined, neither end like the feel / sound of a coil getting caught
up
inside a tube. The tuning is smooth and unobstructed across the full
range.

All told, I get around 432 kc of mechanical travel instead of 500 kc.

The LMO output is supposed to be from 5.0 to 5.5 Mhz. Mine ranges
from
appx. 5.014 to 5.444 Mhz.

The readout is correct - a signal transmitted on 7.2 Mhz. is received
on 7.2
Mhz per the dial.

The construction of this receiver is about the best I have ever seen
on an
SB-XXX kit, so I don't think it's a question of shoddy craftsmanship.
Visual review of the mounting of the LMO, dial, knob, shaft, and
100KC
insert into the spiral on the back of the tuning dial all seems to be
perfect, with no obstructions showing anywhere.

So, that's what I'm looking at ... essentially a perfect LMO, but
with
abbreviated end-to-end travel.

My hope is that I'm just missing something stupid, and it is pointed
out to
me so I don't completely disassemble the unit if I don't have to.

Thanks in advance for the input.

73,
Jeff
W8KZW

Jeff, I don`t have the Schematic in front of me, But, If you will look
at the oscillator circuit of the pto you will probably find a variable
inductor and a fixed capacitor in parallel with it ,forming a tuned
circuit..you will probably find that the fixed cap has changed
value..try changing the value of the parallel cap to about 5% less.Then
the inductor will probably reach its normal tuning range.. I would
remove the PTO (if it`s not too difficult)and run it on the bench until
you get it sorted out .. Good Luck Harold W4PQW

If the low side is stopping at X.055, the high side must be stopping as high
as 590
If yes:

You may have to physically loosen the dial disk shaft screw and "Walk it" to
get the spread center.
Then go to X.000 (this worked on my 301 with the TRW) and use the trimmer
cap to "pull down" to X.000.
If you like mark the shaft befor moving it

See if that works if not you have to operate, I never had to open the PTO on
the SBXX1 series.
Its a simple enough try

-Joe

On Mon, 7 Mar 2005 13:23:17 UTC, "W8KZW" wrote:


The LMO is supposed to tune 500 KC - from X.0 to X.5. Mine physically stops
at X.055 ... in other words, the counterclockwise "end of travel thunk"
comes too early, and won't let me tune the bottom 55 kc of the band. The
clockwise "end of travel thunk" comes where it should. These "thunks" both
sound and feel the same .... as you would expect them to: solid and
defined, neither end like the feel / sound of a coil getting caught up
inside a tube. The tuning is smooth and unobstructed across the full range.

coil in a tube?

The LMO has a shaft with rings on it. The rings have stops that
prevent you from making too many turns. It gives you five turns of
the shaft.

Each stop engages the next ring and is, in turn, engaged by the
previous.

I can't quite visualize how that simple mechanism could be
defective.

Within the LMO, there is a typical worm driven capacitor. No
obvious way that can be defective either.

The question is, how many turns does the big plastic disk make?
Should be a little over 5. If your problem is mechanical, then it's
strictly a matter of counting the turns.

This is a capacitor tuned oscillator, not a PTO.

de ah6gi/4

ckh wrote:
On Mon, 7 Mar 2005 13:23:17 UTC, "W8KZW" wrote:


The LMO is supposed to tune 500 KC - from X.0 to X.5. Mine physically stops
at X.055 ... in other words, the counterclockwise "end of travel thunk"
comes too early, and won't let me tune the bottom 55 kc of the band. The
clockwise "end of travel thunk" comes where it should. These "thunks" both
sound and feel the same .... as you would expect them to: solid and
defined, neither end like the feel / sound of a coil getting caught up
inside a tube. The tuning is smooth and unobstructed across the full range.


coil in a tube?

He is thinking of a PTO where a slug could get jammed inside the
coil form.


The LMO has a shaft with rings on it. The rings have stops that
prevent you from making too many turns. It gives you five turns of
the shaft.

Each stop engages the next ring and is, in turn, engaged by the
previous.

I can't quite visualize how that simple mechanism could be
defective.

Visualize what happens when two or more of the range limiting
disks get frozen together by gummed up grease.


Within the LMO, there is a typical worm driven capacitor. No
obvious way that can be defective either.

Although it is harder, if part of the worm gear has a block of
hardened grease in its tooth, it will jamb the mechanism before
the capacitor can turn its full range. Usually there is enough
mechanical advantage in the worm gear assy that you could over
come the block but 30 year old grease can become quite hard.


The question is, how many turns does the big plastic disk make?
Should be a little over 5. If your problem is mechanical, then it's
strictly a matter of counting the turns.

His wording was difficult, but I got the impression that the markings
on the dial are exactly correct with the received frequency. So that
would mean that there is something mechanical wrong. I would bet on
the range limiting disks being frozen solid with grease or rust.

-Chuck Harris

W8KZW wrote:

The LMO is supposed to tune 500 KC - from X.0 to X.5. Mine
physically stops
at X.055 ... in other words, the counterclockwise "end of travel
thunk"
comes too early, and won't let me tune the bottom 55 kc of the band.
The
clockwise "end of travel thunk" comes where it should. These
"thunks" both
sound and feel the same .... as you would expect them to: solid and
defined, neither end like the feel / sound of a coil getting caught
up
inside a tube. The tuning is smooth and unobstructed across the full
range.

All told, I get around 432 kc of mechanical travel instead of 500 kc.

How many turns of the LMO input shaft does it take to go from end to
end?

The LMO output is supposed to be from 5.0 to 5.5 Mhz. Mine ranges
from
appx. 5.014 to 5.444 Mhz.

The readout is correct - a signal transmitted on 7.2 Mhz. is received
on 7.2
Mhz per the dial.

The construction of this receiver is about the best I have ever seen
on an
SB-XXX kit, so I don't think it's a question of shoddy craftsmanship.
Visual review of the mounting of the LMO, dial, knob, shaft, and
100KC
insert into the spiral on the back of the tuning dial all seems to be
perfect, with no obstructions showing anywhere.

So, that's what I'm looking at ... essentially a perfect LMO, but
with
abbreviated end-to-end travel.

If the shaft takes a bit more than 5 turns to cover the 432 kHz range,
the problem is electrical. But I doubt that very much.

If the shaft takes a bit more than 4 turns to cover the 432 kHz range,
the problem is mechanical. I think that's what's happening. The fellow
who suggested hardened grease or stuck disks is what I'd bet on.

The input shaft of the LMO turns *exactly* 100 kHz per revolution, and
turns a bit more than 5 revolutions stop-to-stop. That's the key to
knowing whether it's electrical or mechanical.

73 de Jim, N2EY

On Tue, 8 Mar 2005 13:22:03 UTC, Chuck Harris
wrote:


He is thinking of a PTO where a slug could get jammed inside the
coil form.


The LMO has a shaft with rings on it. The rings have stops that
prevent you from making too many turns. It gives you five turns of
the shaft.

Each stop engages the next ring and is, in turn, engaged by the
previous.

I can't quite visualize how that simple mechanism could be
defective.

Visualize what happens when two or more of the range limiting
disks get frozen together by gummed up grease.

I just spun an LMO from lock to lock, 521 kHz on the dial. How do
you get from that to his 432?

I have an LMO in my parts bin. Lemme see....

Ah-HAH!

There are 6 tabs, not 5.

Each ring is about 86 kHz.

521
434
347
260
173
86

The width of the tab must be about 14 kHz... seems too wide but
maybe.

de ah6gi/4





Within the LMO, there is a typical worm driven capacitor. No
obvious way that can be defective either.

Although it is harder, if part of the worm gear has a block of
hardened grease in its tooth, it will jamb the mechanism before
the capacitor can turn its full range. Usually there is enough
mechanical advantage in the worm gear assy that you could over
come the block but 30 year old grease can become quite hard.


The question is, how many turns does the big plastic disk make?
Should be a little over 5. If your problem is mechanical, then it's
strictly a matter of counting the turns.

His wording was difficult, but I got the impression that the markings
on the dial are exactly correct with the received frequency. So that
would mean that there is something mechanical wrong. I would bet on
the range limiting disks being frozen solid with grease or rust.

-Chuck Harris


--

ckh wrote:
On Tue, 8 Mar 2005 13:22:03 UTC, Chuck Harris
wrote:

The LMO has a shaft with rings on it. The rings have stops that
prevent you from making too many turns. It gives you five turns
of
the shaft.

Each stop engages the next ring and is, in turn, engaged by the
previous.

I can't quite visualize how that simple mechanism could be
defective.

Visualize what happens when two or more of the range limiting
disks get frozen together by gummed up grease.

I just spun an LMO from lock to lock, 521 kHz on the dial. How do
you get from that to his 432?

I have an LMO in my parts bin. Lemme see....

Ah-HAH!

There are 6 tabs, not 5.

Each ring is about 86 kHz.

521
434
347
260
173
86

The width of the tab must be about 14 kHz... seems too wide but
maybe.

If two of the rings are locked together, they will move as a unit and
reduce the travel by one turn. Your test shows that the LMO moves about
432-434 kHz in four turns.

I bet the problem is purely mechanical. Frozen ring or some such.

73 de Jim, N2EY

I think I have it covered.

I removed the LMO and examined it ... there are two pins, one of which acts
as a stop for the disks / collars for travel in both directions ...
clockwise and counterclockwise. The other pin was extended out enough to
engage one of the collars prematurely ... before the tab hit the other pin.

I tapped the wayward pin back a bit .. away fom the rotating tabs, and now
the last tab contacts the first (left, as you look at the LMO from the
shaft-side) pin properly and provides the requisite LMO travel.

I am a bit surprised that this "right" pin evidently shifted position, as it
didn't move back willingly.

My thanks to all on the newsgroup!

73,
Jeff