admiral 24c15 with 20b1 chassis attempt at restore

[bandersen]

Read the alignment instructions. They identify which to adjust and in what order.

[fumplet]

oh ok perfect.

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sound is really good now. I guess its normal for the sound to have buzzing in it then when the picture comes on, the sound buzz goes away and perfect sound.
On to focus coil, I do have focus coil straight and not angled like before so Im wondering if I can get picture any sharper. Test pattern time I guess.

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I think I might need to clean the cabinet glass or what ever it is. I dont think its plastic. Will windex clean it? Waiting on novus to get here for plastic screen. Installed chassis in cabinet and of course the picture is off to the left. Why I have to crank focus coil to extreme just to get picture centered is beyond me. Maybe I should crank it and call it is what it is. I have the converter box set to 4:3 full aspect ratio. Maybe this chassis was dropped and somehow its bent or needs the tube repositioned. Focus knob is almost to one end so by suggestion, focus coil is still off so if I get focus knob centered then adjust focus coil done. Maybe center the knob and adjust for best focus based on focus coil adjustment farther or closer to tube face? Messed with focus coil again, focus knob ect. focus knob comes in at almost full rotation.
Cant find my usb to put up test image. b & k 1210 test generator I bought has super crappy test image so needs a recap???
Screwed with focus coil and ion trap again and now picture is a hair to the right. Needs to go left a bit. Will post a picture of a test pattern if I locate my usb thumb drive. I guess moving focus coil back out did the centering trick but not sure how to get focus adjustment back in range and centered on knob.

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I had thought much earlier that focus was changing but its not. If only there were test voltages to measure. Unknown what voltage is supposed to be at focus knob rheostat center position

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5 bucks says focus will be better 9nce i plug it back into 117 volts and not 125! Whei i put it back in cabinet i just plugged it in walll outlett. With a resistor adjustment i will be good

[bandersen]

Maybe, but I doubt it. There had a wide operating range. 115-125 VAC should be fine. I think it's more likely it is not position correctly or there's a bad power resistor. I really banged my head with one of these and finally discovered a brand new 750 ohm power resistor in the focus circuit had gone open!

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still trying to wrap my head around how the focus circuit even works. I have positioned the focus coil just about everywhere now. back and forth got me the picture to go left or right, but it took me this long to notice it. the Focus tap on the rheostat goes directly to the power supply 5u4. Oddly enough if the 6v6 tube heaters fail, the focus goes out totally as seen when the 6v6 tube socket was intermittent. I guess I need to come up with a better way to clean tube sockets.

[bandersen]

It's part of the power supply with some of the B+ going through it. Think of it like a filter choke. Any changes in the amount of current being drawn by the set will change the focus. When your 6V6 goes out, the current drawn drops, the electromagnetic field decreases and your focus goes out.

[fumplet]

well that makes sense. I was FOCUSing on voltage measured across it when focus went out. So make it draw more or less current and IM good to center the focus control. I checked the 3k sand resistor that was replaced as welll as the 2200 ohm resistor which measured 2387 ohms so I dont think that is the issue

Oh now thats funny my schematic photo isnt in focus either lol

I replaced the vertical output transformer a while back so if thats not right.....that would draw more or less current and make the focus out of whack since the focus coil and vertical transformer are connected. I dont see any other resistors to check. The 5u4 doesnt have any resistors near it

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well screwed this tv up again. I hear vertical running and I have 10kv at picture tube anode cap but no picture. I mayhave accidentially had meter in amps instead of volts when measuring across focus coil but not sure because negative meter lead wasnt plugged in. Anyway Now I have zero picture. So hoping I didnt permanently fry something making this tv a parts set. I do not know where to look now.
Going to guess the video section is dead, other than that maybe check for voltages. I already checked both fuses and since everythings lighting up probably not fuses anyway.
UPDATE:Im a moron! while tilting the chassis on its side to work on the focus and try a new vertical output transformer, I had bumped the ion trap! Now back to the focus issue. Focus knob when rotated almost fully clockwise is when focus comes in at roughly 80 volts across focus coil, so I need to figure out how to be able to increase focus voltage. Turning focus knob counterclockwise, the voltage drops and I can make the focus go way out of focus. 2200 ohm resistor connect to vertical out put transformer is 200 ohms higher. I need to get more voltage to the focus coil somehow. 87 volts is the max the focus knob will put on focus coil rotated fully clockwise! low voltage power supply is at 128volts and supposedd to be at 160 but focus coil runs off of high voltage so I dont know there.
Would a higher resistance in the high voltage 8500 ohm resistor make the circuit draw less current therefor throwing off the focus? Havnt tested yet but there are actually 2 purple dots that appear on the resistor when I turn it on. Resistor in question is r444 on the cathode of the 6w4 tube. Also the main transformer is making a funny noise but I cannot tell if its normal or not. I should try swapping rectifiers and the power audio tube as well.

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Heck! there is a production change H for improper focus...see production change H grrr where is that? Tube installed for the 6v6 is a 6v6GTY....also might make a difference.

[bandersen]

Do you have an image back?

What production run is your chassis? It should be stamped in a big orange letter in several places. 6V6 variations will make no difference.

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Yes Image is back....knocking the ion trap while flipping chassis over made image go away compounded by the fact i turned the brightness knob down all the way and left it there while tweaking ion trap magnet so basically im my worst enemy here. Now image is back onceci figureed out ion trap and brightness were way off . I ordered 6v6 tubes anyway. I THINK chassis said run 18. It does have 2 fuses which the later sets had according to schematic. The focus was centered at one long ago but i must have done something to make it not centered unless maybe the vertical out put transformer going bad was the cause of focus adjustment going in and out of centered adjustment
I did find out that if you use the wrong power supply, the focus will be off so if you possably are using the 4 tube power supply in a set that required a 6 tube power supply that would cause focus to be at one extreme.

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Have been checking resistors to find any way off and so far none. Only resistor acting funny is the horizonal linearity resistor when set is turned on. Two purple tiny dots appear on it very shortly after set is turned on.
Sitting here staring at the schematic and just not even understanding it. Both sides of the focus coil are tied together through a 3000 ohm resistor. So I have for possabilities low power supply voltage, resistor drifted high, other circuit somewhere not pulling enough juice through focus coil.
Update: Horizontal resistor that had two 20k ohm resistors and a 56k ohm resistor measured 55k so both of the 20k ohm resistors had opened up. Cause of focus being off? We will see.
AMazing! Focus came more twards center of knob adjustment. Since I do not have a 8500 ohm 25 watt or better resistor to stick in there I went with 3 30,000 and one 56,000 ohm and I dont know their wattage so Im not sure IM overloading them or not. The brown 25 watt resistor is just being used as a holder, its totally open. I have 10 of the 56k and 10 of the 30k ohm resistors 5 watts rated to play with so resistor booger soldering job in progress. Decided to go with 56k times 6 which gets me 9k ohms. Question is how much off of 8500 ohms and how far off affects anything. I know the specs say 7500 for a 10 inch crt, so will 500 ohms make a difference? Also guessing everything now has to be adjusted again, since now the ion trap moved twards rear of crt to get the good spot. Temp gun says around 200 degrees at bottom of these 56k resistors but much lower at the top of them and thats just weird but if they arent burning up then Im good and no more magical purple resistor eyeballs. Im done with screwing with adjustable open wire resistors as they damage and open up very easily!
So, tell me Im not imagining things because I had to move the ion trap magnet rearward after dropping from 55k ohms to 9k ohms on the horizontal linearity resistor r444.