Hi--

I probably do not run my TVs enough...turned them on today and came back down in an hour or so and the Sylvania's raster was out. Opened the can and found some evidence of smoke. Seemed to center around 3CU3A tube, which I removed.

Nothing melted...a resistor(?) was blackened a bit but not melted.

Is it possible that if I just get a new 3CU3A and plug it in, this might come back to life? Cheap on ebay.

Screen was fine when I turned it on today initially, but I left the room. Was viewing via UHF mini transmitter attached to cable box.

Thx!

First rule of operating any vintage TV: never, ever leave one running unattended, especially a color set.

I have certainly learned my lesson.....I heard some unusual buzzing sound while listening to an old AM radio....one I had never heard before in the sound of AM interference.....and I immediately suspected one of the TVs....

If it still has sound then it probably has B+ (if not check the B+ supply circuits).
Without the HV rectifier (3CU3) installed, and with the room dark does the Horizontal output tube plate (different from the heater which is supposed to glow) start to glow (red/orange)? If the plate stays dark that is good, but if the plate glows do NOT let it run for more than 1 minute (or damage to that expensive tube may result). If the tube plate glows (commonly called red plating), measure the grid bias. If the grid bias is somewhere around -50 to -75 volts DC then you have proper grid drive (if not the H oscillator needs work). look for shorts on the secondary side of the flyback.

Do you have the schematic for this set? If not look for the Sam's photofact for it. Schematics are essential for troubleshooting/finding your way around in a color TV.

Hi there--

I tried what you suggested, but unlike yesterday with the 3CU3A still removed, its connector was sparking like Frankenstein's lab....and making sparking noises. I turned it off soon thereafter. No smoke or anything. All other tubes looked like they were heating up.

I have attached a pic...the connector is circled in red. Also circled is one pin hole that oozed a little bit of oily stuff. It is also on that pin of the removed 3CU3A.

My problem--do not have a schematic and do not have any diagnostic gear. More of a hobby that a specialty for me. I can solder, replace tubes, wires, diodes, resistors, capacitors, etc, but most of all I am a TV idiot who is much better at restoring transistor radios.

Thanks again, though, I am willing to try to fix it as much as my skills will allow ;-)

I had this crated and shipped from the Chicago area years ago from one of the major collectors in this forum,...can't remember his name but he had a basement full of TVs and was a real pro at repairing 60s sets, along with Lawn Boy mowers!

Oh yeah -- also, the set still has full sound. I also have a new 3CU3A on the way from ebay....about $9 shipped.

If the top connector is creating a healthy arc like that then all the troubleshooting advice I gave is likely irrelevant. Try it with the old HV rect tube back in and see it it produces a raster. If not then you definitely need that tube you ordered. If it does produce a raster as bright as before with the old HV rect in it then there was some other issue that has it has temporarily recovered from.

There should not be anything in the pin of that tube socket to produce an oily substance...That oil is probably grease/dirt that found it's way into the set from outside. It is not bad (and sometimes necessary such as when dirt becomes a conductive path for arcing) to clean HV cage areas.

If you plan to fix the set your self/own it for the long haul you really should pick up a copy of the schematic/service data and keep it with the set.

I am with Tom C. Discharge the CRT & pull off the anode lead.
Pull the 3CU3 socket & clean it with 91% isopropyl alcohol.
Clean all the wires to it & the "cup" also. Put back together with
the new 3CU3 & try it.
BTW dischage the CRT AGAIN before reassembly !
BTW #2 most HV rect tubes DO NOT have a filament glow !

73 Zeno:smoke:
LFOD !

Thanks--!!

I will take all of these steps when the new tube comes....figure I will try it with a good tube first....

Also, discharging the CRT--is that basically just turning on the set without it being plugged in before reassembling with new tube hookup?

Will QD electronic cleaner work as well as 91% alcohol? I have both.

Thx again

To discharge the CRT take a screwdriver with a well insulated handle connect it's metal shaft to the TV chassis with a clip lead and slip the blade of the driver under the HV connector on the top of the CRT bell until a spark is heard or you know your hitting the metal connector.
The best way is to use an HV probe instead of the screwdriver/jumper method, but I'd guess you don't have one (that is another important tool for TV work). Second best is to put a high value (meg ohm and up) resistor in series with the clip lead.
If you don't have a resistor (the HV probe has one inside) in series with the ground the stored HV will tend to bounce back within 30 sec to 1 min of discharge.

Failure to discharge the HV stored in the CRT may result in one heck of a nasty static jolt.

Alcohol is best for HV cages/hardware. If you want to use the cleaner on the socket electrical contacts it should not hurt there.

The guy you got the set from is probably Doug Harland DRH4683 is his handle here and on you tube. Nice person I've bought stuff from him too.

I will follow these instructions....thanks....! (don't need to damage the thing any more than it is)

Yes, Doug was his name and he was nice enough to give me the set....just as long as it made it to a good home that would not trash it. It has lasted a long time.

The same kind of thing had happened to my Zenith 1968 color TV.....but that involved much more smoke and melting. I was in the room for that one. All I did is turn it on, with the others.

Amazing how ghosts get in these machines! ;-)

Ill look up CF16W/DO9 issues in my book but PM me with your personal email and I will scan you the schematic. The 3CU3 should have you back up but take all the good advice here on cleaning things.

Sure, it's sent, thx

I am with Tom C. Discharge the CRT & pull off the anode lead.
Pull the 3CU3 socket & clean it with 91% isopropyl alcohol.
Clean all the wires to it & the "cup" also. Put back together with
the new 3CU3 & try it.
BTW dischage the CRT AGAIN before reassembly !
BTW #2 most HV rect tubes DO NOT have a filament glow !

73 Zeno:smoke:
LFOD !

I'd also clean the regulator socket and cap above the cage - it has full 25KV on it and looks as though it may be just as dirty, judging by the plate cap.

HV loves and attracts dirt - it's a much lower resistance/impedance and may be your only problem.

A couple of thoughts: Quite frequently the HV (red) wire that wraps around the core of the flyback that supplies the filament voltage to the HV rectifier tube 3CU3, breaks down and arcs to the core of the flyback. There is usually 2 or 3 turns around the core of the flyback and they go down into the HV cup that the tube sits in and is connected to the filament pins for the 3CU3. If it breaks down it arcs, smokes, and grounds out the HV, usually ruining the HV rectifier tube. Simple fix, just get some good 30KV or better HV wire, take the socket out of the cup and replace the wire, paying close attention to the number of turns around the flyback core. Yes, there is at least 24KV between the wire and the flyback core. Also another thing that i have seen happen is that the HV cup itself develops a crack or a spot in which the HV will arc through to the chassis. In this case you just need to replace the HV cup. Of course clean all the gunk off of the wires, socket, etc. Sometimes this gooey residue will also cause arcing. Since you get a good healthy arc off the connector to the 3CU3 coming out of the flyback with the rectifier tube removed, I think your flyback transformer is ok. Although the 3CU3 could be weakened or bad and also possibly the horizontal output tube.

Also another thing that i have seen happen is that the HV cup itself develops a crack or a spot in which the HV will arc through to the chassis. In this case you just need to replace the HV cup.

If it is a single point leak you can often fix the cup by, cleaning the snot out of the cup, drilling out the carbon path and filling the hole with RTV silicone (which has a higher dielectric strength than the plastic used in most cups :thmbsp:). It ain't what techs did back in the day, but with some cups NLA it is sometimes the best approach.

Also some sets (IIRC Zenith mostly) used resistance wire for the HV rect heater winding which must be accounted for when replacing.

PM received, D09 schematic and Stan Prentiss list of production changes has been emailed. If yours is a code 2, check if the HV regulator cathode circuit changes have occurred. A regulator limiter diode and 10 meg is added on the other side of the 1K 5%

Good luck with cup repairs, I put a piece of #1/0 HV cable jacket insulation flattened out under the HV cup of a 16" color Zenith (chassis 12A10C15) that had burned a hole thru arcing. It is still holding up after 20 years, my woodshop set.

I drilled out the conductive carbon path first. Not sure if I used RTV but that is a great idea. The black stuff I suppose the same as used on tripler-fly terminals.

The cup to chassis mounting screws were long enough and there was clearance for the tube to be installed

I'd also clean the regulator socket and cap above the cage - it has full 25KV on it and looks as though it may be just as dirty, judging by the plate cap.

HV loves and attracts dirt - it's a much lower resistance/impedance and may be your only problem.


Will do...thanks!

Hi--

I tried most of the above options....I cannot pull the horizontal output tube (is it above the 3CU3?). It has some sort of a round metal ring that locks it into place....I feel like I would break it if I tried any harder....but I did clean its cap. The 3CU3 glowed orange and/or blue....the back of the crt had some blue lighting up and the sounds of a CRT coming up, but nothing in the screen (pic does not show the blue).
I see a crack on the CRT as well. (see pic). I did not notice that before. I pulled out the cap a bit to investigate, but plugged it back in.
Sound was fine, no smoke or arcs.

The tube above the HV rect is the HV regulator....You remove it by pushing that ring down before/while pulling the tube.

If you have HV, blue neck glow, no picture, and a crack in the CRT glass, then your CRT has probably lost vacuum through the crack and is now ruined....Good luck in the CRT hunt.

Yeesh, never saw a CRT go like *that* before. Oh well, at least it was one with the beginnings of a cataract.

Keep your eyes open for a Zenith Chromacolor II with a 23V CRT, no cataract issues and it should be a drop-in swap. There may be minor mounting hardware issues but that's it. They're relatively common and there are probably a lot of NOS units in hiding considering the 4-lead safety cap fiasco.

Yeah, as I said....ghosts in the machine!....How would a CRT crack like that without some kind of impact?
Anyway, sounds like this one is toast, as far as my skill set goes....!
It was worth a try tho and thanks, all, for the advice on this old Sylvania.

Yeah, as I said....ghosts in the machine!....How would a CRT crack like that without some kind of impact?
Anyway, sounds like this one is toast, as far as my skill set goes....!
It was worth a try tho and thanks, all, for the advice on this old Sylvania.

Possibly a poor connection between the HV button and the internal coating of the CRT caused arcing and localized heating around the button, which cracked the glass.:scratch2:

jr

Or someone tried to "pry" out the HV Anode connector. In a hurry, I did it once to a 23EGP22 set. 13 days of worry while the customer mulled over dad's $61 estimate for repair (filter cap, a rectifier and an HV cup...), I'd have eaten a picture tube. In the end, she bought a set at Sears. :banana: I got to junk the Motorola, and breathed again.

The crack didn't curve - it was straight as an arrow, to the side I had pried from...

Yeah, as I said....ghosts in the machine!....How would a CRT crack like that without some kind of impact?
Anyway, sounds like this one is toast, as far as my skill set goes....!
It was worth a try tho and thanks, all, for the advice on this old Sylvania.
I wouldn't trash it, good 23V CRTs are easier to find than Sylvania tube tabletop sets. Swapping out CRTs is fairly easy, it's the setup adjustments that are tricky.

Cool, thanks....I will not trash it.....although I do not know where to find one....
That set was closed up tight....the room is locked, I don't know how anyone would have touched that anode connector....bizarre...!

Any delta-gun color CRT the same screen size form 1965 to the last ones made ~1980 should be compatible. Tubes made prior to 1968 will mark a 23" view-able area tube 25 (ie 25AP22) tubes made after '68 will mark them 23V (ie 23VAXP22). Look for delta gun color CRTs or TVs that contain them for sale.
Bob G has some 25EGP22 CRTs that might work http://antiquetvguy.com/FramesetPages/HomepageFrameSet1.html
The ETF also has a large selection of CRTs that may work in your set. http://www.earlytelevision.org/crts_for_sale_color.html

Or look for a early to late 70's solid state set with a deltagun CRT the same size like an RCA XL-100, Zenith CCII etc.

Thanks!

I have had three quality CRTs ruined by gremlins over the years.

The first two : Zenith 1967 color 25GP22 arced and sheared neck off at CRT bell, under the yoke. RCA 1965 color CTC16X had rebuilt channel master 21FJP22 and worked great, one day I turned on and heard crackles. Necked the same way, with weight of yoke/converge yoke landing on chroma board.

The last was a few years ago, a 1965 metal Zenith 24MC32 with a 21FB RCA HiLite, the neck sheared right at the blue lateral magnet, testing like new just weeks before.:tears: I was so upset, I gave the set to another VK member, who had a NIB crt for it.

lesson learned: NEVER spin anything metal on the CRT neck, like the blue lateral magnet/spring. acting just like a glass cutter, this may have been done before I got it when it was set up.

I have seen hi voltage problems crack the bell, And blow the neck off CRT. Make sure you find and repair the hi voltage problem before you turn the set back on with a new CRT. If this set has pc boards, Re solder the board connections and tube socket pins.
You have a really cool set. And they do produce a good color picture.

thanks!