Lights are on, but nobody's home....Crosley 307TA

[Kamakiri]

Got another weird one....

This Crosley 307TA is a 630 clone, with RCA chassis KCS20J. This has to be the earliest chassis design I've ever worked on.

Complete recap and new tubes. I can hear the horizontal oscillator running the way it should, and adjustable with the horizontal hold control. Have perfect audio. Nothing's hot plating, no smoke or fire after 15 mins of voltage (had to throw that in there just for good measure ).

No raster. Not even a dim one.

This is one of those situations where I wish I had a HV probe, but since I don't, I can't test for HV. Flyback looked to be in excellent shape (at least cosmetically), and of course the picture tube tests good.

This set has some big funky resistors in it, stuff that I can't recall ever seeing, too.

Need a little direction as in what to start testing next.....

[DaveWM]

a few things to try.

do you have a neon bulb? if so tape to a plastic stick a few inches long and hold near fly, look for the bulb to light.

is there an ion trap? of so make sure its adjusted properly

check pin voltages at CRT, often a problem there will cut off the CRT

[Kamakiri]

The CRT heater is glowing properly, but that seems easy enough.....I'll just need a little info here. What voltages should I be getting, and between which pins?

I'll pick up a neon bulb at Radio Shack and we'll see what we can see

There's a big funky ion trap on it. I'd thought of that, but I marked the position of the trap, outlined with a sharpie, before I took the picture tube out, and repositioned it the same way. Figured that should at least get me in the neighborhood.....

[compucat]

Originally Posted by Kamakiri

The CRT heater is glowing properly, but that seems easy enough.....I'll just need a little info here. What voltages should I be getting, and between which pins?

I'll pick up a neon bulb at Radio Shack and we'll see what we can see

There's a big funky ion trap on it. I'd thought of that, but I marked the position of the trap, outlined with a sharpie, before I took the picture tube out, and repositioned it the same way. Figured that should at least get me in the neighborhood.....

If the ion trap is installed backwards it will not work even if installed in the same position. Just a possibility.

[DaveWM]

even if the ion trap was put back EXACTLY where it started, there is no way to know if it was right when you got it. they operate in a very narrow range.

the critical pin voltages are the cathode and the grid, this establishes the overall bias of the tube, if the grid is too negative in relation to the grid, the electrons from the electron gun will be cut off. top of my head I don't know the numbers.

[John Marinello]

The old-times used to remove the anode lead, and see how much of an arc they could pull.

[Kamakiri]

Originally Posted by DaveWM

a few things to try.

do you have a neon bulb? if so tape to a plastic stick a few inches long and hold near fly, look for the bulb to light.

is there an ion trap? of so make sure its adjusted properly

check pin voltages at CRT, often a problem there will cut off the CRT

Got a neon bulb at Radio Shack, and tested for HV. The bulb lit up!

Okay, so we have HV. The ion trap on this set is a weird kind of electromagnet, with wires going underneath the chassis. Never seen one like this before.

Just start rotating it around?

[Einar72]

You could try holding a compass near it to see if there's any field present, but, then I just realized there may be a PM centering setup, which can also aggrivate a misplaced ion trap...

[Kamakiri]

I moved around the ion trap, with no change. However, I played with the controls on the back, and weirdly enough, by moving the vertical linearity control, I was able to get a dim line on the screen, very briefly, then it disappeared....it came down, then went up and off the screen. Moved the control back, then forth, and again a dim line on the screen that disappeared.

It's progress of some kind, just not sure "what"

[old_coot88]

Originally Posted by Kamakiri

Got a neon bulb at Radio Shack, and tested for HV. The bulb lit up!

So.. is this at the anode of the HV rectifier? How much actual DC high voltage are you getting at the "second anode", ie., the anode of the CRT itself? It should be around 8 - 10 KV or so.

The ion trap on this set is a weird kind of electromagnet, with wires going underneath the chassis. Never seen one like this before.

Disconnect one end of the coil and check it for continuity. What resistance does it show?

[DaveWM]

the neon light is just a start, as old coot said, I use it to make sure the HO tube and damper and at least the primary of the fly are working. I use a HV prob myself to check for HV DC at the CRT anode (not big on the arc trick, but then again I have a probe). see if you can see any glow in the HV rectifier (gassy). you need to look at it when the room is dark. Better yet start looking for an HV probe.

[Kamakiri]

I held the neon bulb by the flyback, on a plastic wand.

Maybe I just need to get a HV probe.

[DaveWM]

yes you should, esp if you plan to work on color tv's where its important to set the HV to the correct amount. Get one that goes to 30kv as a min, some have built in mA meters for setting up the HO cathode current as well.

[Kamakiri]

Just placed a wanted ad for one here

As far as the Crosley? Thanks to Bill Cahill, for figuring out that I put on the ion trap BACKWARDS

MUUUUCH better