Am I nuts, or did somebody stick the wrong Hallicrafters S-meter in my
SX-28?

My other (restored) SX-28 has the "backwards" meter, meaning that it rests
to the right when the power's off. When you power up, it moves to far left
at no signal, then deflects to the right under signal.

In the SX-28 I'm currently working on, the meter behaves like an ordinary
("non-backwards") meter you'd get at Radio Shack. It rests to the left when
the power's off. When you power up, it moves to the right, then deflects to
the left under signal. Here are a couple of photos.

The first photo shows the set tuned to no signal (RF Gain turned all the way
down), resting around the midpoint.

http://antiqueradio.org/art/temp/SX-28MeterNoSignal.jpg

The second shot shows the set tuned to a strong local signal (RF Gain turned
up), deflecting full left.

http://antiqueradio.org/art/temp/SX-...FullSignal.jpg

I checked the voltages and connections to the meter, which appear OK. The
resistors leading to the meter are also OK. AVC is working well, and the
S-meter adjustment pot is within spec. The radio's about half-recapped at
this stage. I have done the electrolytics, audio, AVC, and IF caps. Still to
come are the RF & various others.

The markings on this meter look different than the ones on my restored
SX-28, but I had been told by other SX-28 owners that both markings were
used.

The radio's usable in this condition, but . . . funky.

If this is the wrong meter, anybody have a working SX-28 meter you'd like to
trade for it? I assume this one comes from some other (possibly earlier)
Hallicrafters set.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Phil:

I did a quick look through Dachis' book, and see no early Hallicrafters receivers with left resting meters. I suspect
someone replaced a failed movement in your original meter with a standard movement. S-meters of that era were likely
standard meters except for the position of the zero. If you study the design of S Meter circuits, and recall that tubes
were the cost driver, a reversed meter movement was the least expensive way out. Screen current on an AVC controlled
tube provided a cheap way to get a meter to move with signal strength, except it was backwards. If you can engage a
meter repair person, that movement can be made right resting, and the leads reversed inside, and you will be back to
where you want to be. Check carefully and see if the leads to the meter are reversed on the back. If they are, then
the second step above is not necessary, just return the wires to their correct locations. But the mechanical internal
adjustment is still required.

--
Crazy George
Remove N O and S P A M imbedded in return address
"Phil Nelson" wrote in message nk.net...
Am I nuts, or did somebody stick the wrong Hallicrafters S-meter in my
SX-28?

My other (restored) SX-28 has the "backwards" meter, meaning that it rests
to the right when the power's off. When you power up, it moves to far left
at no signal, then deflects to the right under signal.

In the SX-28 I'm currently working on, the meter behaves like an ordinary
("non-backwards") meter you'd get at Radio Shack. It rests to the left when
the power's off. When you power up, it moves to the right, then deflects to
the left under signal. Here are a couple of photos.

The first photo shows the set tuned to no signal (RF Gain turned all the way
down), resting around the midpoint.

http://antiqueradio.org/art/temp/SX-28MeterNoSignal.jpg

The second shot shows the set tuned to a strong local signal (RF Gain turned
up), deflecting full left.

http://antiqueradio.org/art/temp/SX-...FullSignal.jpg

I checked the voltages and connections to the meter, which appear OK. The
resistors leading to the meter are also OK. AVC is working well, and the
S-meter adjustment pot is within spec. The radio's about half-recapped at
this stage. I have done the electrolytics, audio, AVC, and IF caps. Still to
come are the RF & various others.

The markings on this meter look different than the ones on my restored
SX-28, but I had been told by other SX-28 owners that both markings were
used.

The radio's usable in this condition, but . . . funky.

If this is the wrong meter, anybody have a working SX-28 meter you'd like to
trade for it? I assume this one comes from some other (possibly earlier)
Hallicrafters set.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

"Crazy George" wrote in message
...
I suspect someone replaced a failed movement in your original
meter with a standard movement.

Hmm, a light bulb flickers dimly in my brain. That would explain why it
looks stock but works backwards. The case of this meter is split to heck all
around and bound together with friction tape, but I figured that was not
that unusual for such old meters. When I opened the smallest electrolytic
can to restuff it, the danged thing split into about five pieces in my
fingers! But I could believe that somebody pried this case apart with a
screwdriver.

If you can engage a meter repair person, that movement can be made
right resting, and the leads reversed inside, and you will be back to
where you want to be.

Is this something a fumble-fingers like me could attempt? What's involved in
making a movement right resting? I have little to lose at this point . . . .

Check carefully and see if the leads to the meter are reversed on the
back. If they are, then
the second step above is not necessary, just return the wires to their
correct locations. But the mechanical internal
adjustment is still required.

Living dangerously, I reversed the leads on the back of the meter. Now it
behaves the same, but instead of zeroing at the middle (OK, the 7 marker)
and deflecting to dead left (the 1 marker), it zeros at dead left and
deflects off the scale farther left. So I assume further surgery is
indicated.

Thx again for any advice.

Regards,

Phil Nelson

Phil Nelson wrote:

Is this something a fumble-fingers like me could attempt? What's involved in
making a movement right resting? I have little to lose at this point . . . .

Assuming you're not serious about "fumble-fingers" - it is likely
"doable" - though it takes a LOT of patience and you will sacrifice some
accuracy (though IIRC the S-meter system in those radios were "relative"
anyway).

First you want to determine what type of meter movement it is -
hair-spring (likely), taut-band, or other (not likely). If it's a hair
spring (spring that spirals in - in a flat plain) and has both a front
and rear adjustment- then it's likely you can successfully "re-zero" it.
The front spring mount usually has a large loop adjuster that is often
engaged by an eccentric pin from the face that allows external zero
adjustments- the rear usually also has an adjustable spring mount - but
far more "dainty" as it's not intended for frequent adjustment - in fact
most are never touched after first calibration when made. It's this back
adjustment that you want to CAREFULLY turn until you zero the meter at
the right. Be very careful to not kink the spring, etc. - most meters
will have enough play to run them fully across using only the back
adjustment - though with some - you may have to use some of the front
adjustment as well. Since the meter will now be "unwinding" the springs
rather than winding it - the meter's linearity will be less than it
should be - but in this application - I doubt anyone would notice. Just
be sure and check for clearance around both springs as they flex as the
needle swings -- as again - the springs will be "un-winding" now rather
than "winding".

Once reversed - you'll have to experiment some to see how it reacts -
whether it appears that the indicated reading is what you would expect -
or if you need to "adjust" the circuitry a bit to better "calibrate" the
system.

HTHs -
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

Phil Nelson wrote:
"Crazy George" wrote in message
...

I suspect someone replaced a failed movement in your original
meter with a standard movement.


Hmm, a light bulb flickers dimly in my brain. That would explain why it
looks stock but works backwards. The case of this meter is split to heck all
around and bound together with friction tape, but I figured that was not
that unusual for such old meters. When I opened the smallest electrolytic
can to restuff it, the danged thing split into about five pieces in my
fingers! But I could believe that somebody pried this case apart with a
screwdriver.

The meter enclosures in some variants of the SX-28 were famous for
cracking. Crap probably got inside the original movement after the case
cracked, and that's why it was replaced.

This problem is common enough that someone is actually producing a kit
to fix it. For more info:

http://bama.sbc.edu/Lloyd%20Godsey's%20Blooming%20Meter%20Fixer.htm





If you can engage a meter repair person, that movement can be made
right resting, and the leads reversed inside, and you will be back to
where you want to be.


Is this something a fumble-fingers like me could attempt? What's involved in
making a movement right resting? I have little to lose at this point . . . .

I'm not sure I would attempt it. I had a friend once that did this on a
replacement movement on a radio he was fixing (an SX-24, IIRC). The fix
involved reversing the little spring on the base of the needle AND
reversing the internal wires. Nerves of steel doesn't even begin to
describe the economy of movement required to do this. This guy was an
orthopedic surgeon, so it was something he did everyday. Mere mortals
such as ourselves shouldn't even try it. I would definitely take it to a
pro, or look for a replacement meter on eBay. They do pop up from time
to time there.




Check carefully and see if the leads to the meter are reversed on the
back. If they are, then
the second step above is not necessary, just return the wires to their
correct locations. But the mechanical internal
adjustment is still required.


Living dangerously, I reversed the leads on the back of the meter. Now it
behaves the same, but instead of zeroing at the middle (OK, the 7 marker)
and deflecting to dead left (the 1 marker), it zeros at dead left and
deflects off the scale farther left. So I assume further surgery is
indicated.

Thx again for any advice.

Regards,

Phil Nelson




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Nerves of steel doesn't even begin to describe the economy of movement
required to do this.

Well, that leaves me out!

I would definitely take it to a pro

Any recommendations?

Regards,

Phil Nelson

"Phil Nelson" wrote in message
ink.net...
Nerves of steel doesn't even begin to describe the economy of movement
required to do this.

Well, that leaves me out!

I would definitely take it to a pro

Any recommendations?

Regards,

Phil Nelson



Phil

If the replacement meter works properly,
and the modification was done neatly,
why not just leave it alone? If a good meter ever becomes
available, then change it out.

Not many folks would know, or care about the difference.

Pete

"Phil Nelson" wrote in message
ink.net...
Nerves of steel doesn't even begin to describe the economy of movement
required to do this.

Well, that leaves me out!

I would definitely take it to a pro

Any recommendations?

Regards,

Phil Nelson



Phil

If the replacement meter works properly,
and the modification was done neatly,
why not just leave it alone? If a good meter ever becomes
available, then change it out.

Not many folks would know, or care about the difference.

Pete

Nerves of steel doesn't even begin to describe the economy of movement
required to do this.

Well, that leaves me out!

I would definitely take it to a pro

Any recommendations?

Regards,

Phil Nelson

Phil Nelson wrote:

Is this something a fumble-fingers like me could attempt? What's involved in
making a movement right resting? I have little to lose at this point . . . .

Assuming you're not serious about "fumble-fingers" - it is likely
"doable" - though it takes a LOT of patience and you will sacrifice some
accuracy (though IIRC the S-meter system in those radios were "relative"
anyway).

First you want to determine what type of meter movement it is -
hair-spring (likely), taut-band, or other (not likely). If it's a hair
spring (spring that spirals in - in a flat plain) and has both a front
and rear adjustment- then it's likely you can successfully "re-zero" it.
The front spring mount usually has a large loop adjuster that is often
engaged by an eccentric pin from the face that allows external zero
adjustments- the rear usually also has an adjustable spring mount - but
far more "dainty" as it's not intended for frequent adjustment - in fact
most are never touched after first calibration when made. It's this back
adjustment that you want to CAREFULLY turn until you zero the meter at
the right. Be very careful to not kink the spring, etc. - most meters
will have enough play to run them fully across using only the back
adjustment - though with some - you may have to use some of the front
adjustment as well. Since the meter will now be "unwinding" the springs
rather than winding it - the meter's linearity will be less than it
should be - but in this application - I doubt anyone would notice. Just
be sure and check for clearance around both springs as they flex as the
needle swings -- as again - the springs will be "un-winding" now rather
than "winding".

Once reversed - you'll have to experiment some to see how it reacts -
whether it appears that the indicated reading is what you would expect -
or if you need to "adjust" the circuitry a bit to better "calibrate" the
system.

HTHs -
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com