RCA 630TS flyback, how is it mounted?

[Jonathan]

Hello,

I'm restoring a RCA 630TS clone, an Air King A1000. I replaced every electrolytic and paper crapacitor with modern ones, added AC line supression caps in place of the old micas for safety and RF noise supression. I may replace the mica coupling caps in the Video IF section if they are bad. Since all the work is done underneath, I need to figure out how to mount the flyback.

When I received the TV, three recifier tubes were missing from the HV section, and the flyback was free moving inside the HV cage. I removed the cage and I'm unsure how to mount the flyback securly. I can't really figure it out. Is the flyback mounted on the HV cage somehow or is it mounted to the chassis? I think the flkyback is good. If not, I have two other good 211T1 flybacks for a 630TS or clone. I purchased all the missing tubes, and just need to assemble it and put the CRT back in to see if any smoke will come out or not.

If anyone has any ideas, please let me know.

Thanks again.

Jonathan

[Eric H]

The fly should have 4 screw holes on the side.
It attaches to the side of the HV cage.

[Jonathan]

Eric,

Thanks. I'll put it together tonight.

Jonathan

[Jonathan]

Ok, well, I got the set together, powered it up and I get no raster. All tubes light up except the high voltage rectifier that is plugged into the socket that stands off from the chassis. I attempted to discharge the CRT by connecting a wire to the chassis and to a screwdriver, and touched the anode, but I never got any spark at all. Does the HV rectifier tube have a filament that is easy to see glowing?

Also, what is the Lamp in the HV section for? It it used as a fuse? A #47 type lamp was in there, but I replaced it with a #44 lamp. Both don't light up, and the #47 lamp I took out has a good filament. Is it suppose to light?

I have a good flyback for this set, but just wanted to know what to do before I put it in.

Thanks.

Jonathan

[RetroHacker]

Well, there's a couple of possibilities. The flyback may indeed be bad, which would explain why some previous owner had removed it from it's mountings. Or you could have any number of other problems contribuiting to a lack of high voltage or lack of raster. Do you get static on the screen? By that I mean, can you put the back of your hand up to the face of the tube and feel the static? You may be getting high voltage, and not even know it. Try this - turn out all the lights in your workshop and then turn on the TV, and watch the screen carefully. If the CRT is really, really, really dim, you may be getting a picture, you just can't see it because the smallest amount of light washes it out. Another test for high voltage is to get a small neon lamp, and tape it to the end of a pencil or other non-conducting stick. While the set is operating, hold the lamp near the CRT anode connection. Typically, the lamp will glow in the presence of high voltage - it doesn't even need to have leads on it. It's the charge that excites the gas in the lamp. Of course, this is a small screened, immediate postwar set, I haven't worked on anything quite that old. It might not have enough HV to detect like this. That's also an electrostatic deflection tube, right? Haven't worked on anything with electrostatic, so I'm not sure what all will apply and what won't. Good luck, and hopefully, someone who knows more about the set in question can give you some more useful advice!

-Ian

[RetroHacker]

BTW - in reference to your other question about pilot lamps as fuses. I have seen #44 or similar pilot lamps used as fuses before, I think there was something about them that was more desireable than a normal fuse, don't remember if it was that they typically acted faster, or the added resistance or something, but I know I've seen it done before. Once again, I haven't worked on a set like this before, so I may not know what I'm talking about I'm just trying to be at least a little helpful, as well as keep myself busy early in the morning

-Ian

[Chad Hauris]

You can use the neon lamp taped to a non-conductive stick to check out the different parts of the HV system...first hold near insulation of Horizontal output tube plate lead to see if there is HV AC there...then you can move it to the plate of the rectifier. I don't know if it can detect the DC from the output of the rectifier but I know it can pick up the AC at the horizontal output plate, the yoke leads, and the HV rectifier plate lead.

This is for a traditional magnetic deflection set...if it is electrostatic it will use something like a 12AU7 for the horizontal output tube and use a seperate tube as an oscillator for HV.

The lamp may be a cathode fuse on the horizontal output tube...I have installed lamps like this in color sets. In sets having a horizontal efficiency coil you can adjust it for minimum current by adjusting for minimum lamp brightness.

[David Roper]

630TS, a 10-incher, is most certainly a magnetically deflected CRT set. So, in fact, is the the 7" 621TS.

[John Folsom]

Johnathan,

Ifrst, ohms out your flyback for continuity. If it is ope, it is bad. If it is not open, it is likely good. Flybacks generally fail in one of two ways....1) they go open circuit somewhere, in which case nothing much happens, buy you have no high voltage and no raster. Or 2) a short developos between adjacent turns on one of the windings, or the flyback begins to arc, due to dirt or contamination on or inside the flyback, in which case the failuse involves arcing and a very obvious catastrophic failuse.

The pilot lamp should be replaced with a fuse of the proper size. But, when troubleshooting, sometimes a lamp can be used in place of a fuse, as it acts as a nonlinear resistance. It presents a very low resistande when operating with currents well below its rating. Should a faudt develop in the load circuit, causing the lamp to draw rated current, the lamp fialament heats up, becoming a large resistance, and reducing the voltage to the load, thus regulating the overload current draw to some extent. This is only recommended when troubleshooting while searching for short circuitsd or overloads, and is not a technique I recommend.

If your flyback has continuity, you shoud check to see if your horizontal oscillator is operating. This is done easily with an oscilloscope. No scope? Then check the bias on the oscillator tube....if it agrees with the RCA schematic, the oscillator is running. You can often hear the 15Khz whine, if you have adequate auditory bandwidth.

If the oscillator is running, check the bias on the horizontal output tube, make sure the damper tube is good, and make sure the yoke has continuity.

Good luck!

[bgadow]

FYI, from my experience the neon lamp only works on the AC side, not the DC output. A neat trick. Also, if you have HV but no raster check the ion trap (assuming this set still has one-if it used a later aluminized tube as a replacement then it might not) the trap would not have to be far out of adjustment to kill the raster.

[Jonathan]

Hello guys,

The lamp does not light, I get no static electricity from the front of the CRT, I hear no flyback whine, and the lamp does not light. The HV rectifier doesn't seem to light either(is it suppose to?). The horizontal damper (5V4G), horizontal output (6BG6G), and the high voltage rectifier (1B3GT) were all missing, so I purchased some new ones and installed them. Since I recapped everything and installed new tubes, I think the next thing to do is to install the good flyback. I'll check resistance tonight.

Thanks.

Jonathan

[andy]

...

[Chad Hauris]

Also another check is to pull the plate lead off the horizontal output tube (with the set unplugged) and hook up the voltmeter to the disconnected plate lead. You should read the B+ voltage at the plate lead. This checks that the flyback primary portion of the winding and the damper tube is operating.

[Jonathan]

Ok guys, I have an update.

Last night I checked the resistances of every winding on the flyback except the HV winding. Every winding was in spec. The flyback is good. I then went over my recapping and saw that I made a mistake. I connected one of the caps to the wrong terminal on ther tube socket. After fixing that, I checked B+ voltage on the H output tube. It was 30 or 40V below what it should be. I then suspected the 680k plate resistor so I measured it and it read 2.1M! It drifted quite a bit. I never got any farther because I had to leave for work. I'm going to replace it when I get home and check more plate resistors. I checked the voltage on the top electrode of the horizontal output tube in respect to chassis ground and my volt meter measured a little more than 400V as it warmed up. After it warmed up, my meter would beep and go nuts, even though it's set to 1000VDC/750VAC. Silly me, thinking that the resistors would be fine.

I suppose the best thing to do is check all the resistors and replace all that are more than 20% out of spec?

Thanks.

Jonathan

[wa2ise]

Originally Posted by RetroHacker

Another test for high voltage is to get a small neon lamp, and tape it to the end of a pencil or other non-conducting stick.

Careful! A pencil has a conductive core, namely the black part that does the writing. It's graphite, similar to carbon comp resistors. Not good for use around kilovolt high voltages.