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  #31  
Old 02-16-2017, 10:47 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by Mre12ax7 View Post
I will be testing all the voltages on the horiz, output and osc tubes.
I will use my Fluke 87 DMM or my Eico VTVM with the set plugged into a isolation transformer.
Also, check the voltages on the audio output tube. It's used as a voltage divider, known as stacked B+. Try substituting the 25L6 tube.
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  #32  
Old 02-16-2017, 02:14 PM
Mre12ax7 Mre12ax7 is offline
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The audio is working fine I hear static when the volume is turned up ( I made a mistake in my other post)
Voltage measurements: ( taken with Fluke 87, horiz, out plate cap off)
25L6
pin 8 159v Sams 150v
25BQ6
pin 4 136v Sams 135v
pin 5 -37v Sams -32
pin 8 0v Sams 0v (gnd)
6SN7
pin 1 -9 Sams -13 (varies with horiz, hold potentiometer could not get it any lower)
pin 2 182v Sams 135v
pin 5 197v Sams 175v
pin 6 6v Sams 6v
pin4 -.034v Sams -.3
Boost (measured at terminal 1 on flyback)
265v Sams 435v The plate cap is off of the output tube so that could affect that.

The plate voltage for the 6SN7 is way off. Is this related to the dropping resistor?
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  #33  
Old 02-16-2017, 02:18 PM
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High plate voltage is usually indicative of tube not conducting as much as it should.
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  #34  
Old 02-16-2017, 02:24 PM
Mre12ax7 Mre12ax7 is offline
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Should I try and adjust the horizontal osc coil?
Could that affect anything.
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  #35  
Old 02-16-2017, 03:42 PM
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That would change the free running frequency but it's not going to have all that much of an effect. Test it for continuity and check the associated resistors, caps and wiring.
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  #36  
Old 02-16-2017, 03:48 PM
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I would not touch it without a raster on the screen, an oscilloscope, or an ear that can hear H-Osc. whistle in TV's and accurately tune for the right pitch.

With the scope you can adjust the osc accurately, by looking at a composite video source, getting ~2-5 H sync pulses on screen, counting divisions between them, then connecting the scope to the H osc in the TV and adjusting the H coil in the TV till the peaks of the wave form are at or close to the same distance you measured earlier...If it is a synchroguide based osc you should adjust for roughly equal peak and hump height too while your at it.
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  #37  
Old 02-16-2017, 04:15 PM
Mre12ax7 Mre12ax7 is offline
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I decided to once again try the set with the cap on the tube.
After about 30 seconds or so I heard the 15kHz sound of the oscillator and my neon bulb lit up near the flyback. No picture. When I turned the set off, there was the typical vanishing raster that you see when set is turned off. No raster when set is turned on.
Ion trap? Low HV? Bad flyback?
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  #38  
Old 02-16-2017, 04:25 PM
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Check the ion trap (try adjusting for max brightness in dark or nearly dark room), and compare the gun bias voltages to the schematic....May also want to evaluate how the controls effect those voltage versus what the schematic voltages and resistances indicate those controls should be capable of.

If you have a WELL INSULATED plastic handle screw driver then you may want to see how long of an arc you can draw with it off of the HV.
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  #39  
Old 02-16-2017, 04:47 PM
Mre12ax7 Mre12ax7 is offline
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I got a raster!
I had to crank up the brightness all the way but I got one.
I will be borrowing a HV probe sometime from a friend.
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  #40  
Old 02-16-2017, 04:54 PM
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Great!

I'd tweak the Ion tap for max brightness rotate either way a bit then move forward/back a bit...You never know if the last setting was best (it often ain't).
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  #41  
Old 02-16-2017, 05:52 PM
Mre12ax7 Mre12ax7 is offline
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I notice that there is some vertical foldover at the top of the raster.
The Sams says check 12BH7 VOT.
One side checks ok and the other is in the yellow ? range. Could this be the cause.
The ion trap was right where it should be which means low HV or weak CRT (maybe it needs to "cook" for awhile)



BTW I think I figured out why the tube was glowing blue. I had swapped the 6SN7 osc tube with another one from the set. Maybe the oscillator is picky?.

Last edited by Mre12ax7; 02-16-2017 at 08:47 PM.
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  #42  
Old 02-17-2017, 07:35 AM
Mre12ax7 Mre12ax7 is offline
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Status of the set.
I replaced the 12BH7 vert, output tube to no effect. Still has foldover.
There is sound getting trough and I presume video but there is no sync.
Horizontal hold is at the one extreme there is maybe 10-15 horizontal lines.
Turn it too far the other way and HV cuts out and it makes unhappy noises.
Vertical hold appears to keep rolling as well. I have replaced the sync separator tube with another one with no effect.
I am guessing that I should check the voltages on the 12SN7 sync separator?
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  #43  
Old 02-17-2017, 02:29 PM
Mre12ax7 Mre12ax7 is offline
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I have gotten the set to display a picture.
The only thing is that it will not lock on powerup, you have to adjust the horiz, hold.
It seems there is some component that will not allow the set to lock when cold until it warms up after about 2 minutes.
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  #44  
Old 02-17-2017, 03:12 PM
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Is it just the horizontal that is unstable? If so shotgun the resistors and mica caps in the horizontal oscillator, Horiz. AFC and any feedback from the fly. If not do the same for the sync section.
It may be a good idea to adjust the AGC (if present first).
If you rather troubleshoot than shotgun, I recommend getting a can of freeze spray letting it warm up and stabilize then start spraying things with it running. The part that makes it flake out when you cool it is the problem.
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  #45  
Old 02-19-2017, 05:55 PM
Mre12ax7 Mre12ax7 is offline
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The set seems to have quite poor horizontal lock.
I have borrowed a HV probe from a friend and it seems to measure a little over 10kV maybe 11kV. The top half inch or so of the picture when locked seems to pull to the right gradually getting worse, eventually the horizontal lock is lost. Vertical is rock solid. Should I go on a witch hunt in the horizontal oscillator section.
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