19" Porthole Zenith - Page 2 - Videokarma.org TV - Video

Tim · #16 01-03-2007, 10:15 PM

tvdude1:

Here is where I got the stuff I used on my 15GP22.

http://www.2spi.com/catalog/vac/vacleak.shtml

I now have more than I will ever need in 4 lifetimes and it has a shelf life. Send me a PM.

everstan · #17 01-04-2007, 12:47 AM

Perhaps you pros could help.
I have the 1951 Zenith 19" porthole with the 24H21 chassis. The flyback rings good and ohms check but the secondary is suppose to put out about 525 volts to send into the 6W4 damper tube. There is about 350 volts of B+ going into one side of the flyback as it should according to schematics but where it should come out as 525 it is about 300 volts. No HV. The only thing I can think of is that when I received this set the assembly the 1B3 rectifier sits on came loose and I don't have it hooked up right. I rewired the socket but I still have that nagging question...what do you do with the wire that emerges from the metal cup the 1B3 rectifer socket sits on? Can someone please open up their flyback cage on their porthole for me.

bgadow · #18 01-04-2007, 12:16 PM

What is the consensus on this sealer: should it be used on ALL metal/glass tubes or are the 15GP22's the only ones with a problem? I have a couple bw sets with them plus a CTC-5 with a 21AXP22. Especially with the -5 that would be a lot of trouble to go through if not neccesary.

tvdude1 · #19 01-04-2007, 06:32 PM

Hello again, about this vacuseal, do you buy the brush on type or the spray? The spray on would seem to be messy.

John Marinello · #20 01-04-2007, 09:27 PM

Quote:

Originally Posted by everstan

Perhaps you pros could help.
I have the 1951 Zenith 19" porthole with the 24H21 chassis. The flyback rings good and ohms check but the secondary is suppose to put out about 525 volts to send into the 6W4 damper tube. There is about 350 volts of B+ going into one side of the flyback as it should according to schematics but where it should come out as 525 it is about 300 volts. No HV. The only thing I can think of is that when I received this set the assembly the 1B3 rectifier sits on came loose and I don't have it hooked up right. I rewired the socket but I still have that nagging question...what do you do with the wire that emerges from the metal cup the 1B3 rectifer socket sits on? Can someone please open up their flyback cage on their porthole for me.

It should look like there are 3 wires emerging from that cup. One is the anode, and the other two form a loop that wraps around the flyback to supply the 1B3 heater. You're either missing your anode lead, or your 1B3 is cold.

everstan · #21 01-05-2007, 03:07 AM

Hi John,
My Zenith, with the same chassis as yours, is called the Tennyson...very similar but mine has the doors.

There is a 4th wire that emerges from the cup the socket sets in. It comes from #7 pin of the 1B3 and it is this one that stumps me. I currently have it just emerging from the little slit and soldered to the cup. Like a shunt connected with the 500pf/20K doorknob cap below. Not sure if that is right.

The HV anode has no output and the yellow boost wire off the flyback is putting out less than 300v when it should be putting out about 525v. The 6W4 damper is likewise deminished. The horizontial output tubes should be putting 30v on pins 5 & 6 and they are putting out nothing. B+ is about where it is suppose to be at 350V.

All new tubes and completely recapped.

I did disconnect the flyback from the yoke and it rang okay.

I'm lost. Shouldn't the flyback be putting out 525v regardless of other circuits if it is good?

Stan

John Marinello · #22 01-05-2007, 10:56 PM

Quote:

Originally Posted by everstan

Hi John,
My Zenith, with the same chassis as yours, is called the Tennyson...very similar but mine has the doors.

There is a 4th wire that emerges from the cup the socket sets in. It comes from #7 pin of the 1B3 and it is this one that stumps me. I currently have it just emerging from the little slit and soldered to the cup. Like a shunt connected with the 500pf/20K doorknob cap below. Not sure if that is right.

The HV anode has no output and the yellow boost wire off the flyback is putting out less than 300v when it should be putting out about 525v. The 6W4 damper is likewise deminished. The horizontial output tubes should be putting 30v on pins 5 & 6 and they are putting out nothing. B+ is about where it is suppose to be at 350V.

All new tubes and completely recapped.

I did disconnect the flyback from the yoke and it rang okay.

I'm lost. Shouldn't the flyback be putting out 525v regardless of other circuits if it is good?

Stan

Stan,

I hope these photos help.

-John

everstan · #23 01-06-2007, 01:45 AM

John,

That is very kind of you to provide the pics. The photo of the 1B3 assembly is turned so I can't see the little slit in the metal cup under the socket but I don't see any other wire coming out of there so it must be soldered to the cup as I have had. So that doesn't seem to be the problem for my lack of HV.

You can see on the schmatics the 525 volts I am looking for. Your flyback looks like it has been getting hot. I wonder if the RTF sensor safe silicone coating would help that? Also somebody mentioned to make sure the connect to the 1B3 was clean.

I am now reading in Mandel's from 1952 that the flyback power supply depends on the presense of pulses and that these will not appear should the horizontal oscillator (or subsequent stage) fail. So perhaps not getting any more than a 30 or so volt drop from the 340 volt power supply to the horizontal outputs and off the primary may be causing this?? Could that cause no flyback boost?

I don't see anything wrong with that tube or wiring except the socket is really loose but I don't think it matters if the socket itself does not have a good ground?

I feel like incompentent detective...maybe I will change my name to Inspector Couseau.

Einar72 · #24 01-07-2007, 05:42 AM

Hi Stan

I had one of these years ago (with the Phonevision socket), and I almost burned up the flyback the day I got it. I'd only had it on for a few minutes when I heard a crackling sound. I ripped the back off only to find the flyback coating drooping in chunks, like the chocolate on an ice-cream bar that got too warm. I found one of the caps in the damper circuit had leaked down to less than 50 ohms. It was one of those "bumblebee" caps that ironically, folks elsewhere on this site go nuts over. Please allow me to offer a few hard-learned bits to you:

Did you measure leakage on each one of the caps you replaced before you installed them? All the (no matter if new) tubes tested OK? Did you use a de-oxidizing product on the tube sockets? Did any resistors change value AFTER soldering new caps to their tie-point?

Nothing beats a good brand of replacement parts. I often disagree, as gently as possible, with folks on and off this site about their choice of (el-cheapo) replacement parts. You have a hard-to-get flyback in that Zenith, and it would be a shame to lose it (or another unobtainable part) due to a financial misunderstanding. All the caps that are part of the circuits in question here should have a superior dielectric characteristic. A cap rated at the required voltage or higher may do fine for bypass work, but in horizontal-pulse circuits, the B-boost and yoke-coupling caps take a beating, and that same cap can soon overheat and fail...Use caps specifically qualified for use in "snubber" circuits and you'll be safe, and the kid at the parts counter will actually understand what it is you need. My personal choice (if available where you shop) is Sprague's 715P series, worth every extra penny.

Lastly, I you have a 'scope, look at the drive signal at the .001 cap just after the Phonevision socket. If this socket or the jumper-plug gets corroded, then disturbed, you might lose signal. Also have someone else check your rework. You may have simply overlooked something or have solder-adhesion issues. Really get in there and look hard. Good luck!

everstan · #25 01-11-2007, 02:28 AM

The Zenith Porthole continues to mystify me...not that it would take much.
I appreciate your hints and they do seem very likely causing the prob(s) but when I doubled checked all the resistors and caps including resoldering the phonevision socket nothing was glaringly wrong.

I did end up getting HV but I did it by applying Horizontal drive from a Sencore VA62 to the grid (#5 pin) of the 6BQ6 to obtain the correct frequency @ 30V. I also put 130VDC on pin 4 (see schematic posted earlier) to the same horizontal output tube to the tune of 130VDC.
Part of the mystery is that unless I take out the horizontal occillator tube the feed to #4 pin drops way down to the 40'sVDC instead of the 130VDC I need.

I get nothing at all on the picture tube with plenty of HV present and the horizontal occilator tube removed with proper frequency applied.

Is there a vertical problem too which also effects the horizontal or perhaps a bad yoke. (it seemed to ring okay) Any suggestions where I might look next?

Help!!!

Stan