For some very sleepy reason I originally posted this on antiqueradios.com.
I'm moving it to here, the right place.

I am still at the beginning of my project to make a TRK12
out of the parts I picked up at the 2015 ETF convention.

I have not even begun to work on the TRK-12 TV, whose two chassis
came in crates, looking "almost" new and virgin ... but not quite!
There are a couple of 1950s shiny 1/2 watt resistors in there.
We won't know how late it ever operated until it is turned on and
the oscillator frequencies are measured. I have all the necessary replacement
caps. This evening I measured a substantial fraction of the resistors
that can be measured The resistor markings are odd .. its mostly
body - end band - next to end band - other end band is silver 10%.
They are all high ... but less high in the 1k - 100K range than
higher or lower. Replacing most will be lots less cosmetic trouble
than expected ... I'll just repaint the closest physical size in modern
resistors. There are dogbone power ones. The Candohms will get
shamelessly replaced with modern resistors on terminal strips.
Well, I'll probably paint them if the paint
I got can take the heat.
Paper caps are ALL absolutely bad
but look nice and will be very easy to restuff. Almost all wire is cloth and OK.

The radio, an RC-427F one for a TRK 120, is in sad shape.
It got rained on. There was rust on the back which I thougtlessly
removed before a photo. Some coils are toast and will get modern replacements.
All paper caps are so fragile as to be unrestuffable. I have not decided whether to
make new fake shells (not easy!), or just use raw yellow axials. Half the wire
is cloth and probably OK, half is plastic and falling apart and will be replaced
(with cloth). The mechanical works are dirty but not rusted and all the turners turn.
It will get a brand new eye tube and mount (TRK120s had no eye tube).

The cabinet is not actually bad. It can be used as-is. A restorer is coming tomorrow to
look at it.

This is going to take a lot longer than last summer's CT-100.

Doug McDonald

Today's word of the day is unrestuffable :D.

Good luck on the resurrection Doug. Keep us posted and post those photos, every one loves photos.

Doug, I have a bunch of old paper capacitors you can restuff. Let me know what values you need.

I also have thousands of NOS prewar resistors. If you made a trip down you could go through them and probably find everything you need.

Here are photos of the TRK12/120 pieces, first set
of cabinet pictures. The last two are looking straight up,
camera sitting inside cabinet on bottom.

Rest of cabinet photos

First three are radio. other two are TV main chassis

The photos of the TV power supply. The radio power supply
is missing almost all parts.

Question is ... there is something missing in the mounting
for the TV chassis. It has been modified ... note the extra
holes in the front. These will be plugged and now veneer
installed covering them.

But where do the unattached wood pieces seen on the carpet go???
There is no way to install the TV chassis. Does anybody know?

The hole size and pattern look to match the chassis for an RCA 630TS. It doesn't make any sense why that would be mounted down there, but that was my first thought when I saw the photo.

Progress report: I've found a cabinet restorer and it has been sent off.

I've found all hard to find pieces and have all but the radio power transformer,
which is supposedly on the way soon.

I've been working on the filthy radio chassis, which is now cleaned up.
Most but not all of the push buttons and the motor work. I'm now cleaning
up the tarnished push button switches. I have not yet decided whether
to take McVoy up on his offer and get usable old caps to restuff for it.
I can restuff the non-polar electrolytic for the motor. Almost all paper caps in the radio are actually open!

Good luck Doug! Looking forward to following this restore here on VK.

This TV's radio has seen lots of work in the past. Last night I finally got all the push buttons to work. The problem ended up being a very odd one: the mounting for
the whole set had been bent and the latching mechanism was preventing some
contacts from contacting when pushed in.

Also I noticed something for the first time: the motor had been rewired with the wire put on by hand! Its clearly the later light colored Nylon wire and is all scrambled
up. Also all the connections to it had been hacked off and reattached in a very
nasty and unsafe manner. However, they did make it work right. For somebody with a pristine one, how long is it supposed to take to go from one end of the band to the other? Its slow but acceptable.

The cabinet is back from the restorer. He did, in my opinion, a very fine job.
He did, however, punt on decal placement, making me do it with his help.
It came out great. However, there were only channel numbers 1-5 so
that's all we used. I hope they are in the right places, the gap is at
far right.

Also ... are the hinges supposed to have a detent for the correct
angle? They sure don't seem to, though they stay put perfectly well.

Pictures eventually.

Sounds like you placed the channel numbers correctly.

There is no detent. The lid is designed to stay put at any position.

The restored cabinet.


http://www.videokarma.org/attachment.php?attachmentid=187069&stc=1&d=1434331611


http://www.videokarma.org/attachment.php?attachmentid=187070&stc=1&d=1434331611

The restored cabinet.


http://www.videokarma.org/attachment.php?attachmentid=187069&stc=1&d=1434331611


http://www.videokarma.org/attachment.php?attachmentid=187070&stc=1&d=1434331611
Very nicely done. It has a smooth semi-gloss finish that looks very original. It's so fortunate that John Vassos was chosen to design these cabinets. They have a very clean machine-age deco design.

I just looked again at the pictures of my cabinet. The front-on
one is absolutely bizarre, I didn't notice! The left and right hand sides
are not symmetric in shade. But .. they most certainly are
quite symmetric in person. I've never before seen my camera
do something like this.

That is some really nice cabinet work!

I've notice Veneer tends to reflect light unevenly, probably because of the bands of grain, that's what makes it so attractive though.

Finally all necessary parts have arrived. Posted is a photo of the radio chassis in its current stats. That is, rust removed, missing the motor capacitor, and the Candohm and three brodcast band coils (hopeless) detached from their moorings. All paper caps are unrestuffable,
Steve McVoy has graciously sent me defunct ones with healthy cardboard cases. Most sections of the Candohm were long ago open and bridged.
Plastic insulation has crumbled. But the motor drive is fixed and works perfectly (with a suitable cap clipped in of course).

I just looked again at the pictures of my cabinet. The front-on
one is absolutely bizarre, I didn't notice! The left and right hand sides
are not symmetric in shade. But .. they most certainly are
quite symmetric in person. I've never before seen my camera
do something like this.
The flash of a camera can often bring-out things that cannot be seen under normal lighting. Sometimes it can really compliment a cabinet, other times it's unflattering to it.

Your cabinet looks very nice after the restoration work. What a contrast from when you started.

I'm 40% through recapping the radio of this monster. So far only one resistor
was over 18% high and it was 1.5 Meg rather than 1.0, the 6A8 2nd grid resistor, so I left it.The area around the can electrolytic is a nightmare so
I'm not restuffing it ... in any case no one will notice as their eyes will all be in the area of the former Candohm.

I am restuffing the paper caps, but even with McVoy's generous stock
of old ones I could not always use the original size bodies as some diameters
were too small. Nor do all the ends look right ... I'm wondering: will
painting the visible ends (which are hot glue) black with acrylic paint be OK?
Will it flake off?

Acrylic should be OK. Probably too late now, but you can get hot glue sticks in many colors including dark brown similar to the original wax.

Acrylic should be OK. Probably too late now, but you can get hot glue sticks in many colors including dark brown similar to the original wax.

I use a dark brown hot glue to hold the new capacitor inside the old shell. It looks very close to the original wax, but to get it to look even better I actually save the wax that I removed from the old cap. I fill the brown glue almost up to the top of the cap and then melt some original wax to "top it off" at the end. Using this method makes the re-stuffed cap look so good that I have to mark the caps I've replaced because I can't tell them apart.

Oh, man, that cabinet is "To Die For" pretty ! What does the CRT look like ? Its one of those 3-4' long jobs, isn't it ? You're STILL a VERY lucky man...

These are not wax caps. They are either the kind with the little paper
disk at the ends with the cylinder ends rolled over it, or paper tubes
sealed at the ends with some sort of black hard substance that
does not melt at a temperature low enough to keep the paper
the original hue. They can, however, just be pulled out.

I had to remove the volume and fidelity controls
to get to parts under them. I've decided to replace all parts under them
with new ones because this is such a hard chose.

I was able to leave lots of old rubber wires in the RF section alone
because they dangle quite safely in air ... but in the audio section
100% of the non-cloth wire will have to be replaced.

I got like three caps replaced today ... the rest of the time was spent
in disassenbly, rewiring, and having to go back to campus to buy
a new soldering iron tip since my local (5 minute walk) Radio
Shack was sold out.

Oh, man, that cabinet is "To Die For" pretty ! What does the CRT look like ? Its one of those 3-4' long jobs, isn't it ? You're STILL a VERY lucky man...

The CRT is less than two feet long by a little. Its one of the
refurbished aluminized radar tubes. I have not taken it out of its carton.
I have a 12LP4 to use for testing.

I too am pleased with the cabinet. Except for the side
pieces of veneer on the front it was not in too bad shape overall,
just scratched, needing sanding. Also, there was a large chunk out
of the wood cover that fits over the CRT which needed filling in and
covering over with new (and very sharply bent) veneer. They guy was
able to match the original veneer closely enough that he didn't
need to redo the other side. Only the bottom front and back pieces
(plain wood no veneer) were badly water damaged and were replaced.

Little progress today. Two resistors replaced, two rotted wires,
and mostly repainting a whole lot of resistors. I painted the bodies tonight;
tomorrow morning I will paint the end and ring (these are not B-E-D
color code but B-E-ring). I'm using ordinary modern resistors, not
worrying about size as the set had a wide variety of sizes.

Doug McDonald

I got the radio working. 80% of resistors, all capacitors, and 40% of wires were replaced.

I first turned it on with no tubes at all inserted and nothing smelled bad, the
motor tuning still worked. Then I inserted the 5U4G and found that the second-level
HV was too low. It turned out to be what I worried about: I did not restuff the
electrolytics, but hid replacements. One was rather close to the fidelity switch,
and I was afraid to bend the switch contacts too much, so it shorted.

I unsoldered the offending switch lugs and redid them, leaving 1/8 inch
spacing which is fine for this voltage. This fixed that problem.

Then I removed the 5U4G and inserted all the other tubes. No heaters.
I had not used Deoxit on the plug that delivers power to the main chassis.

Then I tried running everything inserted on a dim bulb. Nothing smelled
or showed signs of a short. Setting the switch to TV or phono and touching
the input showed the audio worked.
Setting to radio and tuning around shortwave produced little (the broadcast band
coils are defubnct, that has to wait til tomorrow.) Attaching an antenna
resulted in absolutely normal shortwave reception!

:banana:

chassis pictures tomorrow.

I got the radio finished. The bcb oscillator coil was replaced with
a Meissner "universal" one. The other atnessna and Rf amp plate coils
were rewound. The set now works quite well.


Pictures are, in order, a view under the fidelity switch, after reworking.
Next is the finished bottom, then the front, tghen the top.

Very nice work.

That may be true, but sometimes it is good to be weird.

Today I recapped the TV power supply. Since I am not restuffing electrolytics,
just papers, this was easy. It worked correctly with no load.

But I noticed something odd in the CRT resistor chain: The lowest resistor
in the chain is shown on all schematics as 330K. Mine is 560K.
The schematic shows the CRT "screen" connected at the top of
of the 330K resistor, giving 250V. My power supply has
it attached 470K above the 560K resistor, or 1030K above ground.
All other resistors are as specified. This makes the voltage about 780,
which is what I measure. This is not original. Despite being
in crates, my chassis have clearly been well used an the PS has been
worked on a bit. The original connection was clearly just cut off.

What was going on?

There are four different schematics for the TRK12/120. You need to check them all and see which one your chassis' matches best. They can all be found in the RCA Red books.

Darryl

I have the original RCA manual and the Rider's.

The TV main chassis is for sure a TRK12 because it has no limiter tube.
It has no grid cap on tube 9, no connections to pins 3 and 4,
so it must be the version in Rider's that uses IF grid bias as contrast control.
There used to be connections to pins 1, 3, and 4, but no longer,
they were cut off.

Of course, I am going to use one of the radar tubes rather than a real
12AP4 so that may make a difference in the G2 CRT bias.

Steve McVoy: do you know if the 12LP4 also needs different grid bias,
or is it non-critical for test use?

Question: the video chassis has 2 multitap chassis mount resistors that work
like Candohms but are not. They are constructed differently and look more modern.

If their resistance is OK, is it reasonable to just leave them as-is?

If they show the proper resistance and aren't shorted to the chassis, keep them.

I need to know two things to proceed on this TV:

Are the black (or dark gray) black plastic lozenge shaped capacitors
(150 to 3300 pF) in the TRK12 paper or mica, that is, should I replace
them on preventative grounds? I have proper mica replacements.

Secondly, what pins are what on the replacement radar CRT I have?

I have all the caps except those, the .005 uF paper ones, and the
0.1 uF 300V one replaced. When those parts arrive, today or
Monday from Mouser, and I replace them, (about 40 .005 ones!) I
will be ready to try it without the CRT and HV.

I have replaced only one resistor, the 13k part of the pseudo-Candohm.
All others were only borderline 20% high or spot on ... nothing in between!
And very remarkably indeed, ALL resistors of the same value and type
were within +2% of each other!

I'll check the pins on the CRT when I get back to Ohio in a couple of weeks.

I wouldn't replace the low value caps unless they are bad.

I've completed recapping.

I removed the fuse from the CRT HV supply.

With no tubes except the B+ rectifier inserted I brought it
up on a Variac with a meter on the B+. It got up to
normal voltage with not fuss.

I then inserted all tubes except the horiz and vertical outputs.
Or rather, I tied to. It seems I ordered the tubes for a TRK-120
and I've got a TRK-12. I'm missing a 6F8G and a 6H6.
However both of these, despite what the specs say, are
being used as single diodes. They were temporarily bridged
with (hold nose) silicon.

Again bringing up on the Variac caused no fuss.

Did I mention I was feeding a signal in? I checked the oscillator
frequencies and they are set for modern channels 2-6 as a
rubber stamp on the chassis says. It was set to Ch. 2.

Checking the signal path with a scope showed that it was getting all the way
to the outputs (audio and video).
Fine tuning and contrast (actually grid bias on all IF stages) wore
as expected. The video waveform actually looks rather passable.
The sound sounds OK on 2000 ohm phones (remember that it has
no amplifier.)

Next I checked the sync separator chain and it works fine.
The horizontal osc works and the hold works but the pullin
range is rather small. Is this normal for TRK
12s?

No sweep was getting to the horizontal output grid (no tube, remember).
This was traced to a bad width pot. Turning it caused drive to appear,
and disappear, with loud pops from arcing inside it. I have a modern
one that should work if it can take 300 volts.

The vertical system worked correctly, but again with rather small pullin range.

The B+ for the 2nd sync separator is 7 volts [sic] as shown
on the schematic.

So much for today!

Gradually it is returning to life!

I was wrong about the oscillator frequencies, it was
nearing midnight and I was blindly comparing to
the channel limits printed on the set, not modern
ones. They are still the 1941 set, i.e.
the set with one channel at 50-56 MHz. This means only
channels 3 and 4 work with modern signals.
There is no "major" oscillator adjustment in the set,
so I'm leaving it as-is.

The problem pot was taken apart and examined. I could find
nothing wrong with it, so cleaned it up, used deOxit on it and
added a Mylar film insulation layer between the terminals
and the case front, which was uninsulated and rather a close
gap. It now works fine. This was a really high-class part
in its day.

A photo of the chassis at present is attached. The big blue
13K power resistor is obvious. There are numerous Nichicon
radial electrolytics scattered around .. some are invisible in
the photo. Only one small resistor was replaced, with a modern 1/2
watt carbon one (the one meg one). Other ones of that sort
were original. There are two unrestuffed .005 uF caps, due
to worries about installation damage if restuffed. There are
also of course the two silicon diodes across the two missing tubes.

I now have to await word on what the radar CRT connects are,
make a protective box for the 7.5 kV rectifier, and make an
HV connector adapter. It also needs a small
dropping resistor, only 5 to7 volts..

Coming along great, looking forward to a working screen shot. :thmbsp:

Gregb

Coming along great, looking forward to a working screen shot. :thmbsp:

Gregb

It produced a (negative) picture on my scope.

Oh yes, one more question.

I took the radar tube out of its box and examined it.

I was told that it had an outer Aquadag coating, forming the
filter cap usual on later TV CRTs.

I notice no such coating. The front 2/3 of the bell insides
is aluminum coated, the back 1/3 and a couple of inches
back into the neck is Aquadag coated on the inside ...
but no Aquadag on the outside. I even tried scratching a bit
off at the edge with my fingernail, nothing came off.

If you've used one of these, was it outside coated?

Aquadag is useless in prewar TV sets. The purpose is to act as a capacitor to smooth out the 15 kHz from the flyback in postwar sets. Prewar sets used transformer power supplies with 60 Hz, so all the filtering is done in the power supplies with capacitors.

Yes, I knew aquadag was useless for such a set. But I had recalled somebody
saying it was there.

Incidentally Steve, I found the CRT base pin assignment, it was on
a paper formerly glued to the base but now loose.

I looked at the alignment: the video IF as amazing: it looks like the CT-100
its so good. The RF was not so good: on neither Channel 3 nor 4
was the audio really in range of the fine tuning though you could
hear sound. And 3 and 4 were off in opposite directions. And the
correct spot was out of range on the adjustments by a lot. I got Ch. 4
OK by a slight bend of the strap but Ch. 3 required that I solder
a copper strip 1/4 inch wide to the tuning loop to get the inductance
down a bit. The tuning adjustments for the antenna coils were
well within range and were quite a bit off of flattest response.

Oh yes: the audio carrier ended up at 8.11 MHz.

Today's progress: spent over three hours standing at a lathe
making a special HV connector to attach the cup connector
to the old connector. It been 15 years since I did extensive
lathe work, but I still remember it all.

Oh yes ... did I mention that I didn't take shop class
in high school ... rather, at Harvard. Yes, we had a noncredit
shop class in the chem department!

Tonight I attached the yoke and plugged in the H and V output tubes and the damper, and turned it on. It worked OK and nothing bad happened. I'm
using a horizontal output tube ostentatiously labeled "Fender" and not ostentatiously labeled "made in Russia".

RCA specified a special version of the 6L6 for that set. It is metal. If I remember correctly, you can identify the proper one by a double metal ring at the bottom rather than a single one. I have no idea how modern tubes would work.

I got a picture on the thing tonight.
The sweeps seem to still be OK. The cathode and
grid signals to the CRT seem reasonable ...
say +75 on the cathode and -5 to +25 to +50 on the grid.

However the CRT G2 and focus seems totally out of whack.
With those K and G1 voltages I get normal brightness but very very
bad focus. If I either increase the video drive or decrease the
cathode voltage ... making it excessively bright ... I get good
focus but its very unstable.

I set the resistor chain on the HV to the ratios given by the
schematic ... the set came with the G2 set way up the
chain from what the schematic says.


Does anybody with one of these radar tubes know what the
correct G2 and focus voltages are?

Doug McDonald

The only difference between the radar tube and the 12AP4 voltages is the filament, which is 6.3 rather than 2.0. Focus and G2 are the same: about 250v for G2 and 2000v for focus.

Let me get those voltages for sure right. They are referenced to the
cathode, yes???? So with the cathode at +75 the G2 should be at
75+250 = 325 and the focus should be adjustable around 2075, with
respect to ground.

The instability is perhaps due to bad resistors in the bleeder chain.
I will replace them today.

Close examination of the HV cable showed it to have cracked
rubber insulation. It was replaced.

I forgot to mention that the grid lead to the CRT was dead.
It used a very small wire, like #36 or so, presumably for
low capacitance. It was broken. I replaced it with #24 wire.

Those voltages are absolute - not relative to the cathode. They are from the factory manual schematic.

I'm sure you have checked the 7500v line?

Focus voltage won't be precisely 2000, and in some cases I've had to change the divider to get a voltage that will produce a focused picture.

You are right about the 2000v focus ... its very wrong. The resistor
chain values on the schematic give more like 1400 and result in
correct focus near the center of the control.

I changed all the resistors to modern carbon ones, using two or three
2-watt ones in series for each of the originals to get enough voltage
rating.

I have no idea if this helped, however.


That's because I discovered that the focus wire to the
original socket was open. It was NOT OPEN yesterday morning, because I
measured it when making the adapter for the radar tube. But it
sure is now. How can a wire go open? This is not a small gauge wire,
its like #22 stranded. I did not cut open the bundle it is in but replaced
it with a new HV wire cable-tied to the bundle.

I did cut about 1/2 inch off it at the socket end and 2 inches inside
the chassis. I stripped the ends expecting to find that the shortened
wire was OK. No, its open. How can such a wire be open?

In any case the set now produces a quite nice picture. Its not without
defects. First is what looks like interference but probably
is beats between the audio and color carriers. I've got to figure
out where the audio trap is and check its adjustment.

Second is blurring due to too much capacitance from the grid lead.
This varies with placement. I will make new cables with 0.005 inch
wire, and also make spacers to keep it away from the rest
of the bundles.

Other than that, the set now works correctly.

Part of the blurring and the interference lines were only on ch.4, not 3. The lines
indeed were audio-color beating.

The cause was a misadjusted RF coil in the tuner. Now both 3 and 4 produce nice pictures.

Great news. Congratulations on getting it working.

I'm sure you know that with the low IF frequencies this set has horrible image rejection. I never attempt to feed them with anything but a single channel (3 or 4).

I have a rubber mask for this thing that came with the cabinet.

However, this morning I tried fitting it in the cabinet and on the tube
and it appears to have shrunk. It would seriously restrict the
view compared to the area of the wood mask. Is shrinkage normal
or at least precedented?

If it is not normal, and no proper replacements I exist I can of course
kludge something out of foam.

This ad on the ETF classifieds page:
Reproduction TRK-12 rubber CRT masks, $100 a piece. Contact Barry Kasindorf, barry at barrykasindorf dot com 508-528- 0026.

Don't know if it is still current

-Steve D.

Depends on what you mean by shrinking. Attached are a couple of photos that show what a good one looks like.

I got all the parts in the cabinet safely and it works. The mask is indeed
the right size.

All that's left is a permanent bucking transformer, which I have plenty of.
I'm currently using a variac.

The only problem I had in putting it in the cabinet is that the
picture was rotated 180 degrees. I didn't feel like removing the tube to rotate the yoke
so I reversed the leads instead. The la
st 1/4 inch of the leads were somewhat dicey
anyway so this had an added bonus of safety.

Another TRK12 lives.

I'd LOVE to see some pics if at all possible!! :yes:

There is not much more to show than what is already posted.
Look earlier in the thread.

You are not getting a photo of the current underside of the TV
power chassis! First, I forgot to take one before installing it
in the cabinet. Second, some people might puke if they saw it,
all those triples of modern Allen-Bradley style 2 watt carbon resistors
replacing the originals. I had to buy the type of resistors that
our EE department storeroom stocked since I wanted them
in a hurry. I could post a picture of the removed (and 30-50% high resistance) originals.

Its not ready for a frontal shot, running, as the knobs for
it were only put "in the mail" yesterday.
There is no back.

However, I should and will post a picture of the HV
connector I built for it. As I said, I have not run a lathe for
somewhere between 15 and 20 years [dedicated to the
memory of George Pisello who taught me], but it turned
out quite nice. There was lots of work with a boring bar.
I will also post a picture of the HV rectifier running in
the perforated sheet metal cage I made for it.

As promised, two pictures. The HV box is self-explanatory.

You can see the old HV connector through the Plexiglas
of the connector I made to hook to the rubber cup type
modern one. There is an aluminum cylinder inside that
mimics the size of the connector on a 12AP4.
Note that the old wire was replaced by a modern red one.
The screw on the side prevents the old connector from
being pulled out, a safety hazard.

This ad on the ETF classifieds page:
Reproduction TRK-12 rubber CRT masks, $100 a piece. Contact Barry Kasindorf, barry at barrykasindorf dot com 508-528- 0026.

Don't know if it is still current

-Steve D.

I know him well he still has some left.

My ears were burning..Here are some pictures of the TRK-12 masks I have. I have 2 left.
-Barry

The mask I have is now obviously the correct size.

Its just that I would have made it the same size as the
mask in the glass cover, with worse cut off corners.

Photos in operation.

Looks great!

Gregb

That is impressive.

Zowie! What a project.

Phil Nelson

Very impressive. Nice job.

-Steve D.

That looks about as good as a 630TS! Great seeing these pre-wars working. It kills me when owners choose to leave them unrestored.

Not quite as good as a 630TS or my 9T249.

Its not by design, however. The radar RT, and presumably also
the 12AP4, suffer from space charge blooming, or perhaps
its the lack of bypass caps on the CRT G2 and focus. At very low
brightness it really is very sharp. As I said, the IF frequency response
rivals the CT-100. Solid color areas have very obvious color
carrier in the picture. The tonal scale is nigh onto perfect.

Well done!! Thanks to posting the pics!!

now that my friends is a television!

Doug, have you replaced the two HV capacitors in the 7500 v power supply? Checked the resistor between the capacitors? Checked the 7500v line while turning up the brightness?

Though the picture on our set get somewhat out of focus as you turn if you turn up the brightness too far it doesn't bloom.

The HV does not collapse. Blooming is probably the wrong term.

It looks like space charge, curable only by higher anode voltage.
The tube I have can generate dangerously high brightness.

The resistor has been replaced, and both caps appear to be in good shape.
Their capacitance measures OK at low voltage, they do the job, and
don't get warm.

One question for somebody who has a very original one:

WHERE is the loose clip-on pilot light that comes
out of the radio power supply supposed to go, and do?

On the front, right below the bars over the speaker,on the 120 cabinet only.

The radar tube is much brighter than the original 12AP4 because of modern phosphors and aluminizing.

Ah yes! There is the spot for the lamp.

But it does not work because the restorer had to completely
replace the front bottom piece of wood due to terminal rot
and of course had not been instructed about the lamp.

I will return to Plan A and construct a small mount to make a suitable
spot of light on the rug under the set.

Wow, very nice picture on your set!

Additional pictures, made on a tripod.
The weather one has the high temps showing only one
field, so the scan lines show. The criss-cross pattern is
color dots. Pictures are grayscale.

The chroma info passing the IF so well makes me wonder if during the field sequential/early NTSC days if anyone ever added a color wheel to a pre-war set because it was handy and not valuable at the time....It would be darn cool to find a prewar set with such a vintage modification.

One more question: My set does not have a back, and I don't really care to
install one, as it just heats this up (though these sets are very well ventilated).

But if I should find one: are the backs for the TRK-12 and TRK-120 different?
My cabinet is a TRK-120.

The backs on these sets are a completely open metal mesh on a small wood frame. They do not cause heating inside the cabinet. The back is the same for both versions.

Darryl

Another note for TRK12 users:

While I did not notice it on program material, I noticed
a considerable (say 1/8 or 3/16 inch) bending of vertical lines,
moving at the usual 60 vs 59.94 Hz beat frequency. This could only be from
hum pickup from the heater power, or magnetic fields, since
it clearly was 60 Hz hum, not 120 Hz.

Installation of a cylinderical Mumetal shield on the
area between the socket of my radar tube and the yoke cured it,
so it was magnetic. This was a shield made for a
2 inch photomultiplier.

My experience has been that for these noncritical applications
a 1/16 or 1/8 inch wall plain steel tube , degaussed first,
would work fine.

Does the long persistence phosphor in the radar tube not mess with moving images?

The CRT is one of those that had the phosphor replaced by a real year 2000 or so P4, is
aluminized, and has a new gun. Only the glass bell is from a radar tube.

The chroma info passing the IF so well makes me wonder if during the field sequential/early NTSC days if anyone ever added a color wheel to a pre-war set because it was handy and not valuable at the time....It would be darn cool to find a prewar set with such a vintage modification.

I didn't notice this comment before. I have no idea if anybody did that.
The actual picture resolution of the 9T246 you sold me is just as good.
However, the IF response, swept, is not quite as good as the TRK 12. As I
mentioned earlier, in the TRK12 it is stellar: in fact it actually, really, no quibble,
is as good as the CT-100, which is as good as any RF-based set
can be. Note that the IF of the TRK12 is 8-12 MHz or so.

And remember ... on screen, with a 441 line picture, the horizontal resolution
of the TRK-12 would be better than ANY true NTSC set.

I'm restarting this thread.

I got a bee in my bonnet about my (this thread's) TRK-120 radio (its for sure a TRK-120 radio as it has no feedback switch nor eye tube).
The TV continues on it way as a I reported above.

Electrically the radio works perfectly. Mechanically the motor system also works perfectly and stops nicely. The push buttons have
proven somewhat dicey. The push buttons themselves were sticky and a big problem. In a two hour marathon I managed to
get them all off and reamed them out with a 1/8 inch end mill. This fixed that.
But the contacts on the push button bars are flaky and seem to require constant
attention with DeOxit. I suspect that the only cure for this is to take it apart and
gold plate everything heavily.

But that's not the major annoyance. The radio/amplifier works perfectly on TV shows
or voice-only radio programs. But on our two local AM music stations (which I need never actually listen to on it of course) it is abysmal. Its more abysmal at the
bassiest setting. It sounds like the speaker bottoms out. These stations DO have excessive low, very low, frequency bass. The radio has a built in bass boost at
low volumes that can easily be fixed if one wants nonoriginality. Is this a characteristic of the speaker mounted in an unclosed cabinet, or does it need
a rebuild job?

Also, the volume control has returned to scratchiness. Last summer I inquired
about a replacement and somebody said they had one. BUT ... would it be equally troublesome? Mine worked perfectly after removing the tin whiskers and using
DeOxit on it.

Should I punt and install a modern or st least late-40s/50s control?

I spent hours yesterday playing with this thing (TRK120 radio).

Main problem is the speaker. It is original and works. All coils are working correctly. The cone was indeed rubbing and vibrating badly at low frequencies.
Its paper and hopelessly fragile. I tried shimming the cone in places with
squishy form to damp out the problems, this works OK but clearly will eventually fail due to cracking the paper.

There are places that recone old speakers. Has anybody else had one
of these speakers redone, or a similar one? It is a very garden variety late
30's 12 inch electrodynamic one with an attached push-pull output transformer and hum bucking coil. The frame is in first class shape. And suggestions about where to have it reconed?

I seem to recall that some speaker rubbing can be fixed by getting the cone wet and letting it dry with the speaker cone facing up. Might be worth a try before paying for a recone.