1000th post :banana:

What better way to celebrate than another restoration project ? This one's a real doozey!

Here are a bunch of videos if you'd rather watch than read :D
Sentinel 430 restoration - part 1 (Overview) (http://www.youtube.com/watch?v=MR47-GuOThs)
Sentinel 430 restoration - part 2 (Time to start recapping!) (http://www.youtube.com/watch?v=sbMCOjAo6AY)
Sentinel 430 restoration - part 3 (Finally, some real progress) (http://www.youtube.com/watch?v=QISVAyU5H0o)
Sentinel 430 restoration - part 4 (More steady progress and a few surprises) (http://www.youtube.com/watch?v=MJmAB_FXhvU)
Sentinel 430 restoration - part 5 (Time to finally test the full size CRT!) (http://www.youtube.com/watch?v=xoT9yEWytzo)
Sentinel 430 restoration - part 6 (A final twist and putting it all back together) (http://www.youtube.com/watch?v=6_gjhsAtfOs)


I received a tip on a picture tube that's compatible with this set. I'd never really checked it out other than determining that the CRT is weak. So before dropping some money on a replacement I figured I'd do a quick recap and slowly power it up. What I thought would take a few hours turned into four long, late night sessions :drool:

Here's the set. I got it a while back in Skokie, IL from the nephew of a woman that had worked in the Sentinel plant in nearby Evanston during the war. It had been in the same house all this time and it's in great condition. The only minor flaws being the 'piece sign' stained speaker cloth and a break in the CRT gasket.
http://farm4.static.flickr.com/3394/3411048906_9158351a09_b.jpg

Weak CRT
http://farm4.static.flickr.com/3339/3429883849_3476e45395_b.jpg

Here's the chassis. Copper plated so no rust to remove for a change!

http://farm4.static.flickr.com/3409/3410898166_c4fe846e46_b.jpg

http://farm3.static.flickr.com/2783/4351788215_e6a6c22f9e_b.jpg

I had to use a heat gun and some vaseline to get the CRT out. There's probably a joke or two in there somewhere :rolleyes:
Then I dug right in and tacked in new electrolytics beneath the two cans. I also replaced all the big yellow ones below. I slowly powered it up slowly and all the tubes lit up nicely :D
http://farm5.static.flickr.com/4026/4351789215_3cdafd8a26_b.jpg

My excitment was short lived though: no sound - not even a hum, no video, no HV. What could the problem be :scratch2:

I measured B++ it was about 75v too high. I remembered leadlike had a similar problem (http://www.videokarma.org/showthread.php?t=246203&page=2) and I checked the filter choke. No voltage drop across it. I tested the choke and it's around 100 ohms.

I started tracing the path after the choke and discovered that it runs through two low valued wire-wound pots for vertical and horizontal centering. I checked the vertical pot - bingo it's open!

I didn't have any replacements on hand so I built a little substitute using 10 ohm resistors.
http://farm5.static.flickr.com/4018/4351789521_b766528908_b.jpg

I powered up the set with my little patch and was treated to some nice white noise from the speaker that responded to the volume control :D Instead of HV though I got a loud squeal. Time to check around the horizontal circuits. I replaced a bunch of caps and resistors, but still no luck :(
http://farm3.static.flickr.com/2738/4351788919_3401f4c20d_b.jpg

I checked out the flyback and it seemed ok so I widened my search and replaced a few more caps. Finally, I got rid of that bug, ugly bumble on the far left and got 10KV :thmbsp: Still no picture though. I was going to call it a night until I noticed a flash of light on the 8XP4 test CRT as I turned the set off.
http://farm3.static.flickr.com/2701/4351841075_2899085cc7_b.jpg

A little more work and I had the first image of sorts.
http://farm3.static.flickr.com/2779/4352587498_28fa39d6ba_b.jpg

That was it for day 2.
On to day 3 and more recapping and resistor checking. Making some real progress now.
http://farm5.static.flickr.com/4020/4352587700_76fe22c25f_b.jpg

Good enough to pop the full size CRT in and see if it has any life left.
So close!
http://farm5.static.flickr.com/4052/4351841827_b0d2172f04_b.jpg

A little more work and :rockon:
http://farm3.static.flickr.com/2778/4351842091_a55457f53f_b.jpg

However, that's with brightness and contrast at 100% with all the lights off. If I back off on either, the picture quickly fades to black. It's not very pleasant to watch so I fear the CRT really is weak.

So much for a quick recap, but I do know for sure that the set is viable and worthy of spending a a little money on.
I really hate those bumblebees - they look cool but cause so much trouble :uzi:
http://farm5.static.flickr.com/4055/4351881803_c73ac4c5f8_b.jpg

...An' ANOTHER one about to spring to life...

Now for the cabinet. Luckily there wasn't much to do. Just some Weiman's furniture polish took care of the "colorfast Blond Korina" wood. Here's the original sales brochure: http://www.tvhistory.tv/1951-Sentinel-Brochure.jpg

I found a date scribbled on the back that confirms it's from 1951.
http://farm3.static.flickr.com/2796/4352626654_e38242eeb6.jpg

Here's that stained speaker grille.
http://farm3.static.flickr.com/2705/4352627300_2398fd8509_b.jpg

http://farm3.static.flickr.com/2764/4352626970_c5e51f0f45_b.jpg

I used some detergent, stain remover and bleach to clean it. No more peace sign.

http://farm5.static.flickr.com/4026/4351881189_ae629bb3a4.jpg http://farm5.static.flickr.com/4064/4352627920_a2a78832f5.jpg

I hooked up the internal antenna and did a test with my agile modulator.
http://farm4.static.flickr.com/3337/3410894230_e6157176ed.jpg

http://farm3.static.flickr.com/2598/4351900937_4a36cbb86c_b.jpg

Not the best picture, but there's still some work left to do.

...An' ANOTHER one about to spring to life...

Yep, nothing like being snowed in to get loads of sh*t done :yes:

GREAT!:banana::banana: That is one fine looking set!

Have you tried to re-activate the CRT yet? What is the tube, a 16KP4 ?

jr

GREAT!:banana::banana: That is one fine looking set!

Have you tried to re-activate the CRT yet? What is the tube, a 16KP4 ?

jr

Thanks! No, I haven't. I've never used that function before and I'm a little wary to try. Plus, I have another idea or two to test out. If all else fails, I certainly will use it.

I don't know what CRT this is - it's unmarked. The schematic states a 16KP4 or 16RP4.

http://farm5.static.flickr.com/4010/4351788555_61f80a242b_b.jpg

...re.

I bet a modern CRT tester would brighten up that CRT with little to no risk. Don't try with the B+K 440 I see in the picture.

Roger that! I have a Sencore CR70 now. Back when I took that picture a year ago or so, I only had the B&K.

Nice work. Good to follow the steps. And I'm amazed that speaker grille came back to life, I would have thought you'd have had to replace it.

While I pondered my next step with this set I remembered I do actually have another 16" set. It's an Airline/Monkey Wards GSE-3020 I picked up last spring.
http://farm4.static.flickr.com/3579/3514257896_6306a0c9e3_o.jpg

The previous owner said he had been watching it up until it gave out shortly before he sold it to me.
I did get a decent raster on it when I briefly powered it up last year. It has a CRT marked 1-3-64.
http://farm3.static.flickr.com/2797/4352018417_d9f0d0c186_b.jpg

http://farm5.static.flickr.com/4030/4352764910_f47fa2cc96_b.jpg

Hmm - something looks awfully familiar about it :scratch2:
http://farm3.static.flickr.com/2787/4352019037_ab02f55805_b.jpg

It's the same freakin' chassis :eek:
A couple minor differences like the speaker field coil instead of a dedicated choke and a hybrid module instead of discrete for the vertical integrator.

How weird is that ? I wonder if both of them outsourced to the same manufacturer. I wish I had doubled up on my capacitor order to cover this set too!

Here's a closer look at that CRT. Hey, it's been rebuilt. Check out the angle on that gun.
http://farm3.static.flickr.com/2752/4352765510_0edc30ca69.jpg

http://farm3.static.flickr.com/2774/4352765792_ddfbf0ce7a_b.jpg

I popped it in the Sentinel and discovered the dimensions are a bit different. That caused the focus and center to be a bit off, but I'm not going to adjust that stuff for this test. It's definitely brighter but seems pretty harsh no matter how I set the contrast :scratch2:
http://farm5.static.flickr.com/4020/4352019797_e2615e4382_b.jpg

I may be all wet here (the mind is the second to go...I don't remember what the first was), but I think somebody posted a picture of another brand set that was determined to have the same chassis as your Airline... does that thread ring a bell?:scratch2:

jr

I'm not sure, but I did a little search of 'Airline' on this site and found my own from when I found this set. Apparently, it originally used a 16TP4 CRT. I'm not sure what the current one is.

Nice work. Good to follow the steps. And I'm amazed that speaker grille came back to life, I would have thought you'd have had to replace it.

Thanks. I thought I would too. I tried two different stain removers, but bleach is the only thing that really had an effect. Maybe it's whiter now that it was originally, but I'm OK with that.

There's nothing like a little flash of light on the screen to mess up a night's sleep!! I've done that, too. About to call it a night, and then something positive happens unexpectedly... "Oh geez, can't go to bed now... I'll never get to sleep!"

That's awesome the way your speaker cloth came out! On the other hand, I think the peace sign was kinda cool! :D :beatnik:

Making progress... getting close! Won't be long now! :banana::yippy::yippy::banana:

There's nothing like a little flash of light on the screen to mess up a night's sleep!! I've done that, too. About to call it a night, and then something positive happens unexpectedly... "Oh geez, can't go to bed now... I'll never get to sleep!"

That's awesome the way your speaker cloth came out! On the other hand, I think the peace sign was kinda cool! :D :beatnik:

Making progress... getting close! Won't be long now! :banana::yippy::yippy::banana:


LOL - I was until 4am that night http://www.jawaspot.com/smilies/tired.gif I kinda liked that piece sign too, but the stain had to go.

Although I haven't given up on this CRT, I couldn't resist picking up this Motorola chassis with a 16RP4A for $15

I hope it arrives in one piece!

Does anyone have a schematic specifically for a Sentinel 430 ?

I'm currently working from Sams set 124 Folder 9 which covers models 420, 423 and 424. That's the best they had to offer. It's close, real close, but I'm encountering subtle differences in the sync separator, dc restorer and horizontal circuits.

I also checked Beitmans 1951 which has 412-416, 420, 423, 424. Beitmans 1952 has 438-444 :dammit:

It's been a couple very, very frustrating weeks, but I think I'm in the home stretch. First, I liberated a replacement pot from my Airline set. Then, I discovered that not only did the sync/dc restorer circuit differ markedly from the schematic, but some parts were only connected at one end! Apparently, someone was tinkering with it way back when. I decided to rebuild it from the ground up according to the schematic.
Now I had a much brighter picture, but the horizontal sync went to hell :smilemad:
It appears I was wrong about this CRT - it still has some life in it :thmbsp:
http://farm5.static.flickr.com/4022/4377657082_c46b55f43f_b.jpg

So, I started putting old parts back in (or new parts with the old values regardless of what the schematic called for) following the reference picture I had taken. Finally, when I got to the horizontal phase inverter, I got my sync back :D
Only problem now is the retrace lines are very prominent.
http://farm3.static.flickr.com/2740/4376907531_ef5e429daf_b.jpg


I remembered seeing an article at the ETF on a retrace mod and dug up this page (http://www.earlytelevision.org/vertical_blaniking.html). I was surprised to find that this mod was already in this set, but it wasn't doing the job. I experimented with the RC values and finally, got a bright, stable picture with no retrace lines :banana:
http://farm3.static.flickr.com/2762/4376907785_12ba448d49_b.jpg

Time to fire up a test pattern and get that picture all squared away!

Hey that's awesome!!
:banana::yippy::grnbounce:yippy::banana:

Yeah, sometimes it seems there's simply no mercy, and then when you least expect it, it works!

Congrats! :thmbsp:

I have one of those B&K 440's it always show the crt as worse than my Sencore CR-70. And always the CRT seems better than what the 440 says.

Also the Sencore seems very good at the rejuv mode, have had good luck with it.

just something to think about.

My parts chassis with a 16KP4A arrived today. It was really, really well packed!
http://farm5.static.flickr.com/4039/4386915702_fd74ed238e.jpg

http://farm5.static.flickr.com/4065/4386152861_183f5698b6_b.jpg

It turns out this a very nicely restored Motorola chassis. Does anyone recognize the handy-work ?
http://farm3.static.flickr.com/2753/4386153179_1940982407_b.jpg

I wonder what happended to the cabinet :scratch2:
http://farm5.static.flickr.com/4011/4386916496_d6b4e591f8_b.jpg

Here's the GE 16KP4A.
http://farm5.static.flickr.com/4017/4386915994_0f13c5b452_b.jpg

Unfortunately, it reads absolutely 0 on both my CRT testers :( :tears: :dammit:
Maybe it's just a loose cathode connection inside the base cap ?
http://farm5.static.flickr.com/4001/4386916802_16246d3f89_b.jpg

I suppose worse case scenario I have a really nice parts chassis for my Motorola 12K2 and a tube for Hawkeye to rebuild.

I remembered seeing an article at the ETF on a retrace mod and dug up this page (http://www.earlytelevision.org/vertical_blaniking.html).


Thread jack: That's a pretty simple mod, I'd like to use it on my Philco which shows retrace lines at high intensity. Problem is on the Philco, the pic tube cathode is used for brightness and the grid is driven by the video amp tube. How could I change this simple circuit to work with the grid vice the cathode, if that's even possibe? I assume I'd need a phase inverter, and a coupling cap at the very least.

Looks like someone's done all the hard work for ya on that one! Yes, one of the pins in your socket could need resoldering. I had a NOS 21EP4 that gave a dead element on one of the pins and feeding more solder in the pin fixed that... then tested like new.

And if resoldering the pins doesn't help you can always try the re-weld the cathode trick as a last resort.

John

Thread jack: That's a pretty simple mod, I'd like to use it on my Philco which shows retrace lines at high intensity. Problem is on the Philco, the pic tube cathode is used for brightness and the grid is driven by the video amp tube. How could I change this simple circuit to work with the grid vice the cathode, if that's even possibe? I assume I'd need a phase inverter, and a coupling cap at the very least.

I'm glad you asked - I had the same problem with this set!
What I did was feed the vertical pulse into the cathode along with the brightness control and leave the video grid alone. It wasn't working at first because the 0.05 cap on the cathode was filtering it out. So i cut that down to 0.02 and reduced the resistor to 3.9K.

I hope this helps.

And if resoldering the pins doesn't help you can always try the re-weld the cathode trick as a last resort.

John

I took the base off - it was loose already. It's not a bad solder joint :tears:

Here's the best photo I could manage. To my eyes it looks like the cathode connection is OK, but I can't see all of it. What's the cathode re-weld trick ?

http://farm5.static.flickr.com/4022/4387839823_b49f1605c5_b.jpg

I'm glad you asked - I had the same problem with this set!


:grnbounce
:yippy:

Every once in a while I get lucky!

Thanks, I'll have to give it a shot.:thmbsp:

that chassis looks a LOT like the motorola TS-14 I am working on.

It's a TS-60. I have a TS-23 that looks the same too. They made a bunch of chassis that were all very similar.

This is from the Sencore CR31A SuperMack manual, so I don't know if it works with all rejuvenators.

If a CRT indicates absolutely no emission, and the filament is still working, an open cathode is indicated. When this occurs the automatic controlled REMOVE G1 SHORTS circuite of the CR31 can be used in an attempt to weld the cathode. (goes on to talk about resoldering the pins first).

1. Set the BEAM BUILDER function switch to the REJUV 2 position and allow the filament to warm up for 60 seconds.

2. Set the Function switch to the REMOVE G1 SHORTS position and IMMEDIATELY press the REJUVENATE OR RESTORE button before the filament has time to cool. At the same time, tap the neck of the CRT.

3. If a flash occurs in the CRT neck, release the REJUVENTATE OR RESTORE button. Return to the CRT TEST section and check the CRT for emission. If no flash occurs and/or no emission can be read on the meter, the cathode cannot be welded to restore performance.

John

:banana: :banana: :banana: :yippy: :grnbounce :guitar: :boink:

I cannot friggin believe that actually worked!

I followed your directions about 30 times with no luck. Just as I was about to give up I saw a brief flash. Still no emission though.
About 6 more blasts, whacks and flashes and I finally got it welded back on. The emission is really strong too!

I think it would have been easier if I had a 3rd hand :scratch2:

Thanks you so much for those crazy instructions. What a great forum :D

Time to try it out in the set. I'm kinda afraid to move it now though :para:

http://farm3.static.flickr.com/2737/4389532280_40ff8ffaef_b.jpg

How cool is tthat! :banana:

Great success story! Thirty times NO and then a big YES. :beerchug:

I admire persistance!

My old boss had a poster on the way, "never give up" with a frog choking a bird that was in the process of swallowing the frog.

In contract negotiations the idea was aways the same, "out last'em"

WOW! it is nice to know that works! :banana::banana::banana:
A few months ago, I gave up on a 14" tube in a small DuMont portable... the cathode would connect on occasion if the neck was tapped, especially if the heater voltage was elevated, but it would not "stick". Since the set came with a spare jug, I just went ahead and changed it out. When I autopsied the gun, I found several additional welds that were very poor...somebody was having a bad day at the CRT plant. :sigh:
Does Scotty (or anybody else) have the equipment to do a Laser rework?

jr

More good news :) Here's a preliminary picture with the 16KP4A in the Sentinel chassis. I still need to do some tweaking of the focus coil, yoke etc. I'd say it's about 15% brighter and sharper than the other tube. I wonder if some of that is due to the dag coating which the other tube lacks.

I'm not sure which tube I'm going to leave in the set :scratch2: Either way it's nice to have a spare :yes:

http://farm5.static.flickr.com/4008/4389584854_390df3ae34.jpg http://farm5.static.flickr.com/4052/4389584948_4888c7cec5.jpg

Nice, good to hear you were able to re-incarnate it!:thmbsp:

I hooked it up to my B&K 1077 and tweaked as best I could. There are a few issues to resolve:

The top is clipped.
The brightness increases from top to bottom. You can see that in the earlier pictures too.
The upper-right corner is dim.

I've done the best I can with the ion trap magnet, focus coil and yoke. Any thoughts ?

I think I'll poke around the vertical circuitry first to fix up the top of the picture.

http://farm5.static.flickr.com/4063/4391448750_6dcc1a095a.jpg

---

Thanks! That sure does look similar and you've done a nice job on it :thmbsp:
It's good to know some else out there is working on one too. Other than the little 7" 400 series, I don't see Sentinels too often. I have the Sams and Beitman's for the 422 if you need a copy.

I've just about got this set all squared away. First issue - the top being clipped and twisted was due to my 1077B being out of whack :stupid: I really need to properly overhaul that bugger.

Second issue - the brightness gradient was due to the CRT being mounted at a bit of an angle. See that gap at the top - the tube is tilted back a little in the yoke.
http://farm3.static.flickr.com/2719/4407533081_fb81847406_b.jpg

I fixed that up and the brightness is uniform now. I just need to tweak that yoke rotation and lower the picture a little to take care of those dark bottom corners. So close to being done :D
http://farm3.static.flickr.com/2784/4408301096_493617d76f_b.jpg

A few more tidbits about this set.

It has 14 channel positions - one blank before #2 and one blank after #13 ?!?

It also has a color converter. Would this have been for a color wheel ?
http://farm5.static.flickr.com/4022/4389910665_dcd3b47536_b.jpg

While looking through my parts stash, I came across a NOS Merit HOT for this chassis. Between that and the spare CRT, I should be able to keep this set running a long, long time.
http://farm3.static.flickr.com/2801/4390680132_db0176e18c.jpg

Is this a big drum tuner? It's likely those blanks could have strips installed for specifc UHF channels that were in your area... and they gave you provisions for two channels instead of just one.

I think it would be really cool to find an early set with a UHF channel strip installed. It's always possible to have one and not realize it. It would be easily overlooked. The tuner drum in my Zenith PH has a empty spot where one could easily be installed. The drum on my Bendix does not. Makes me wonder about the Sentinel 7" sets... there's an extra click in the tuner and it's not labeled on the bezel.

Greetings from FixitLand!

Is this a big drum tuner? It's likely those blanks could have strips installed for specifc UHF channels that were in your area... and they gave you provisions for two channels instead of just one.

I think it would be really cool to find an early set with a UHF channel strip installed. It's always possible to have one and not realize it. It would be easily overlooked. The tuner drum in my Zenith PH has a empty spot where one could easily be installed. The drum on my Bendix does not. Makes me wonder about the Sentinel 7" sets... there's an extra click in the tuner and it's not labeled on the bezel.

My '52 Zenith K1846R has a Channel 27 strip instead of Channel 3. When the set was new, KPTV Channel 27 was the only station in Portland, Oregon. We didn't get a VHF station until KOIN-TV 6 came on in 1953. Unfortunately for me, the folks from whom I got this set misplaced the Channel 3 strip long ago...

Take care,
--
J. E. Knox "The Victor Freak"

My '52 Zenith K1846R has a Channel 27 strip instead of Channel 3.


Nowadays, Ch 3 is the most important spot on the dial for us! Too bad they didn't stick that 27 strip somewhere else. It's a good thing most all VCR/DVD machines, modulators, and satellite boxes, etc. give you a choice of using Ch 3 or 4.

---

I have the Sams,thanks for the offer.The pic on yours looks great now!:thmbsp:
My set needs a flyback, the wires to the HV rectifier,and to the HO tube,were
ripped out when I received the set.I was able to dig them out,reattach them,
and reassemble with hot glue,and then a coat of varnish.The repair seemed to work for awhile,but now I can actually hear arcing sounds from the fly itself. Of course this will not stop me from finishing this set,this is the fun part to me, because once the set is working,it just gets stacked up with all the other working sets.
Pat

Ditto. As much as I like my old 10" B&W sets, I don't watch them often. Most of the fun to me is in bringing them back to life and cleaning them up real nice. Then I push them to the back and pull out another dead one to work on. I have a dozen sets waiting out on the back porch :D

I have a dozen sets waiting out on the back porch :D

I bet that statement can apply to many of us here! :yes:

I bet that statement can apply to many of us here! :yes:


Not here. 1950's vintage TV's are rare as $3 bills.

I'm calling this project officially done. I even stuck a TV lamp on top :D

http://farm5.static.flickr.com/4003/4409657599_6d41c33ca7_b.jpg

Is this a big drum tuner? It's likely those blanks could have strips installed for specifc UHF channels that were in your area... and they gave you provisions for two channels instead of just one.

I think it would be really cool to find an early set with a UHF channel strip installed. It's always possible to have one and not realize it. It would be easily overlooked. The tuner drum in my Zenith PH has a empty spot where one could easily be installed. The drum on my Bendix does not. Makes me wonder about the Sentinel 7" sets... there's an extra click in the tuner and it's not labeled on the bezel.

I think so, but it's under a metal RF shield and hard to get a good look at. Do you think a tuner designed for VHF could go up to UHF frequencies :scratch2:

Apparently the answer is yes based on my experience and I could kick myself now for not truly appreciating it: a 1951 Zenith porthole I once owned (a VK member has the same set as his avatar) picked up o.t.a. channel 35 in the channel 2 position. I bought it from an antiques merchant who claimed to have gotten it from a very elderly couple whose primary set it had been since new. That was in 1991. If true, the original owners sure had one ace TV technician at their disposal considering channel 35 didn't come on the air until the set was about 20 years old!

That is a neat TV lamp. Like to find one to put on top of my 1950 Zenith Porthole TV.

Is it an antique or is it something that can be easily found today?

Vintage TV lamps are so popular that they have a category all their own on eBay. I see 231 listed today.

http://collectibles.shop.ebay.com/TV-Lamps-/13864/i.html?_armrs=1&_mdo=Collectibles&_mspp=&_pcats=4053%2C1404%2C1

Phil

Vintage TV lamps are so popular that they have a category all their own on eBay. I see 231 listed today.

http://collectibles.shop.ebay.com/TV-Lamps-/13864/i.html?_armrs=1&_mdo=Collectibles&_mspp=&_pcats=4053%2C1404%2C1

Phil

Well I be darn. Did not know.
Never heard of a TV lamp.
Even not knowing, they are still visually appealing.
I guess this shows that some designs are timeless.

I think so, but it's under a metal RF shield and hard to get a good look at. Do you think a tuner designed for VHF could go up to UHF frequencies :scratch2:

I have a Sentinel similar to yours... trying to remember... that shied isn't easily removed?

It would seem those UHF channel strips are specifically designed to work in the VHF tuner. The original tuner strips are usually numbered on the strip, so, follow the numbers as the drum turns. If you come across a number that doesn't fit in the sequence, then you've got one.


Vintage TV lamps are so popular that they have a category all their own on eBay. I see 231 listed today.


That's the truth!! They've got some crazy lamps out there, too!

I think so, but it's under a metal RF shield and hard to get a good look at. Do you think a tuner designed for VHF could go up to UHF frequencies :scratch2:

Some sets, particularly Zeniths, had turret tuners with removable channel strips which could be replaced by UHF strips. The latter would be inserted in place of unused VHF channels in a given area. For example, if your area had channels 2, 4, and seven, and a new UHF channel went on the air on channel 52, you could get a UHF strip tuned to that channel, insert it in an unused position in your TV tuner, and presto, you would now have reception of the new station (provided, of course, that you had the proper UHF antenna; in the days of UHF channel strips, this usually meant a good outside antenna, although if you were very close to the transmitter you could get by with a loop or an indoor UHF antenna).

The maximum number of UHF channel strips that could be installed in any TV tuner is theoretically 12, although in most areas that number was somewhat smaller, especially in New York and Los Angeles which already have seven VHF channels. In these cities, a maximum of five UHF strips could be installed in the tuner, in place of unused channels 3, 6, 8, 10 and 12. In most metropolitan areas, however, there are far fewer VHF stations, so the number of UHF strips that could be installed in the tuner could be as great as nine or 10, although I doubt if any major US city (with the possible exception of Los Angeles) has anywhere near that many UHF stations. In my area near Cleveland, there are only three VHF stations on channels 3, 5 and 8, which leaves nine unused positions. However, there are (never have been) nearly that many UHF stations in this area; before digital, we had UHF channels 25, 43, 55, and 61. When UHF channel strips were popular, Cleveland only had one such station (PBS, then NET affiliate WVIZ) on channel 25, so only one strip would be required, and in fact the MATV (master antenna TV) distribution system at the local elementary school in my old neighborhood downconverted that station to channel 4, so no strips were required or used in those sets to receive the station; as a matter of fact, our TVs were all RCAs which I don't think could have been used with UHF strips.

I think the idea of using UHF channel strips to receive such stations on unused VHF channel positions was patented by Zenith early on, and could not have been used by RCA or any other TV manufacturer without risking a patent infringement suit--or worse. However, there is a way set owners could set up their turret VHF tuners to receive only the local VHF stations in their area--by removing all strips occupying unused channel positions, leaving only the strips for the active stations in the area. This would allow the viewer to switch from one local station to another without going through unused channels, and would also allow the use of UHF strips in the unused positions. Using my area as an example, grouping channels 3, 5 and eight together would leave nine unused channel positions, in which UHF strips for channels 25, 43 and 61 could be installed (further reducing the number of usused channels to six). This would afford the viewer the convenience (especially when tuning by remote control) of tuning to his or her desired station without having to flip through unused channels 2, 4, 6, 7, 9, 10, 11, 12 and 13, as is possible with today's electronic tuners which have an add/delete option for setting desired vs. undesired channels in a customizable scan list. The unused VHF strips could and should be saved in case the set owner moves to an area with different channels; of course, this would mean getting new UHF strips for the different UHF stations in the new area.

Needless to say, however, this is an outdated method of setting a TV tuner for receiving only the area's active channels in this day and age of electronic tuners. It cannot be used with older sets nowadays anyway, as older sets used with ATSC->NTSC converter boxes require that the VHF tuner be set to channel 3 or 4 and left there, all tuning (and presumably on-off power switching of the TV, not to mention volume control and muting) being done either at the box or via its remote.

I think so, but it's under a metal RF shield and hard to get a good look at. Do you think a tuner designed for VHF could go up to UHF frequencies :scratch2:

I grew up in an area that only had UHF at first, and would say that they sorta worked. Strips were not recommended for fringe reception. Although the strip had tuned circuits for the UHF channel, gain must have been very low. I believe the oscillator was run at a sub-harmonic of the desired frequency and then multiplied by components contained on the strip. At the time, continuous UHF tuners seemed to work better than the Standard Coil tuner strips. Few had RF amp circuits, but some UHF band boosters were available. Poor converters and low power transmitters made for a fairly poor television debut, but what the heck...it was TELEVISION!!! :)

jr

I have a Sentinel similar to yours... trying to remember... that shied isn't easily removed?...


Maybe, but I gotta pull the whole chassis first and my next project is already up on the workbench. I'll take a look one of these days and let you know what I find.

That's the truth!! They've got some crazy lamps out there, too!

There's a whole website devoted to them: http://www.tvlamps.net/
What a collection!

Well I be darn. Did not know.
Never heard of a TV lamp.
Even not knowing, they are still visually appealing.
I guess this shows that some designs are timeless.

TV lamps were used to provide a soft light on top of the set so that the room in which the set was located wasn't totally dark when the TV set was on, per recommendations by eye doctors of the time (1950s) discouraging watching television in pitch darkness. IIRC, my folks had one of these TV lamps on top of our first set; it was in the shape of a horse, with a little 7-watt Christmas tree bulb in the base.

Some of the fancier TV lamps even included a digital clock in the base. One manufacturer of these lamps (don't recall whom right now) had a TV lamp that was actually shaped like a miniature television, with the clock in the center of the "screen" and the lamp arranged so that it illuminated the area around that screen and the clock as well. The clock mechanisms were motor-driven digital clocks made by well-known companies such as Pennwood Numechron, the same folks who brought us the first motor-driven electric digital clocks.

I wouldn't be surprised if we eventually see a comeback of these TV lamp clocks, with updated designs, including LED clocks, of course. The diffuser could be in the shape of a current TV actor or prop from a popular show, and the lamp bulb would probably be an energy-saving LED or other low-power light source.

I have a few of those numechrons too.
http://farm5.static.flickr.com/4053/4366844289_6420940a51_b.jpg

Thought I'd bump this thread to the top because Bob's done a couple recent reveiw videos on this set. I've been finding it very fascinating because I picked up this sets bigger brother earlier this fall. Basically it's the same chassis but with a 19AP4 CRT. Originally I picked up the model 425-CV because I was in need of a good 19AP4 for my DuMont RA-119. But the more time I spent researching the Sentinel, the more I wanted to keep it complete. Recently I finished restoring the chassis. The cabinet is in decent shape and only needs a little touching up. I currently have the chassis back in the cabinet and have been watching it over the holidays. Turns out it's a fine performing set.

http://i452.photobucket.com/albums/qq245/Kuehn/Sentinel%20525/Sentinel525006_zps610c7f3b.jpg?t=1388859445

http://s452.photobucket.com/user/Kuehn/library/Sentinel%20525

Beautiful set :thmbsp: I hope you had an easier time with service info that I have. I've never found a 430 specific schematic and the 423/425 info doesn't quite match mine.

So as Kevin mentioned, I have pulled the Sentinel out for some servicing. All this time I've been running it on the weak CRT it came with but it's nearly dead and needs replacing.

http://farm8.staticflickr.com/7367/11578361753_67479bdbdc_c.jpg (http://www.flickr.com/photos/70039806@N00/11578361753/) http://farm9.staticflickr.com/8092/8559047462_f1749ec93e_c.jpg (http://www.flickr.com/photos/70039806@N00/8559047462/)

I guess the sales flyer claim of 17" was accurate after all.
http://farm3.staticflickr.com/2851/11761196644_2d14ac0955_c.jpg (http://www.flickr.com/photos/70039806@N00/11761196644/)

Here's a shot of how the set was playing. The CRT lacks focus and it gets worse as the brightness is increased.
http://farm6.staticflickr.com/5508/11578476944_281ec683ce_c.jpg (http://www.flickr.com/photos/70039806@N00/11578476944/)

Back when I got this set I had assumed it had an early 16" CRT in it, but it turns out I was wrong. If I had just peeled back the rubber trip on the CRT I would have found this label showing it's a rebuilt 17BP4!
http://farm8.staticflickr.com/7332/11611258015_4ce200a5e1_c.jpg (http://www.flickr.com/photos/70039806@N00/11611258015/)
So I can't really using the nice aluminized 16KP4 I found :( I do have a couple good 17BP4s although neither is aluminized. I chose the one with the best external coating and installed it.
That's too bad though because it means my 17T13 with dead CRT (http://www.videokarma.org/showthread.php?t=254976) will have to wait. I then checked all the tubes, found six weak and/or shorted and replaced them.

Back when I restored this set the first time around, I had noticed a gradient in the brightness. Here's a shot of the same issue with the new CRT. I suspected it had to do with the vertical retrace blanking circuit. So I disconnected it and the brightness is now uniform but the retrace lines are back. I'll play around with different RC values and see if I can get it working correctly.

http://farm3.staticflickr.com/2834/11678716345_03e24822ec_c.jpg (http://www.flickr.com/photos/70039806@N00/11678716345/)

Think I ended up with a .01uf and a 5.6k in series for retrace blanking. There's definitively a trade off between max blanking and brightness at the top of the screen, as well as overall condition of your CRT.

Here's the signal on the cathode. It's pretty obvious now why there's a brightness gradient.
I reduced the cap from 0.1 to 0.01 and increase the resistor from 1.5K to 5.1K and it helped a lot :)
http://farm3.staticflickr.com/2893/11785981626_ec8abbe79f_c.jpg (http://www.flickr.com/photos/70039806@N00/11785981626/)