Magnavox Color Roundie

[DaveWM]

check resistances of coil L36 all terminals

[DaveWM]

dont forget to wiggle the tube when the set is on.

[tvcollector]

I try and measure the voltages at pin 7 of the osc tube.. Each time I power off and on again and measure again, I get a totally different readings..

Update: seems to be stabilizing at +28 volts..

I've wiggled tubes and all that too.. There's 5 different terminals coming off the horz osc..

[DaveWM]

if if the tube is getting +28v at the grid the tube or some part will be quickly distroyed, assuming B+ is still getting to the plate and the cathode is still connected to the ground thru the coil, check pin 8 per the sams.

[DaveWM]

Originally Posted by tvcollector

I've wiggled tubes and all that too.. There's 5 different terminals coming off the horz osc..

thats right and resistance readings are on the sams.

[DaveWM]

you should confirm the circuit ground states are good, and watch this video, I have seem flakey tube sockets on other sets as well

https://www.youtube.com/watch?v=y4vkDchJRyI

[tvcollector]

Sams shows 23.5 ohms between 5 and 3, and 57.5 between 4 and 5.. None of the terminals are in order or labeled on the pc board for the osc coil, and the only one I can ID is the one going to ground.. I've measure between the 4 terminals in every way and I don't get anything at 23.5 ohms or 57.5 ohms.. I get 25 ohms between two of them and 65 ohms between another two, is the closest thing I can get.. I checked for continuity at the pin and the solder joint for each pin while tube is still in socket, probe of my ohm meter is thin enough... The new tube that I replaced is good but at the lower end, and it passes shorts and grid emissions..

[tvcollector]

I cleaned the volume/power switch with a little WD40 and the power switch is flaky..

[DaveWM]

pin 8 to ground resistance is?

[DaveWM]

check pin one
voltage and resistance per sams on the horz osc. Do this with the horz out tube removed from the socket to avoid damage.

[tvcollector]

Had to take a break from the project due to weekend jobs.. I'm back on it..

Pin 8 to ground is 50ohms
Pin 1 to ground is 22.5k
Pin 1 voltage is at 25VDC

Replaced alot of the caps and a few resistors and still no change..

[tvcollector]

Doing B+ source checks on the sweep board I'm getting around 435 on the 405 and 410 voltage test points.. It's slightly high for both, but is it still normal?

265 volt check point seems to be right dead on..

Come to find out it's the osc coil, I was able to get -120 at pin 7, then when I started touching the osc coil, the meter started jumping over over the place.. I've got a replacement coming from Moyers..

[tvcollector]

There was a bad solder joint on the old Horz Osc Coil.. Was able to get the voltages at -114 at pin 7 and -55 volts at the Horz output tube... Still I can't get the MA in the ballpark.. I can't get it under 240ma.. It also jumps around into the 300ma range when adjusting the horz hold control.. I replaced the old coil with the new one and makes no difference... I think the flyback is toast, I replaced shunt tube and other tube and hv only comes up to around 5000v..

[Electronic M]

Could there be an HV arc or short loading it down?

[tvcollector]

I'm not sure.. Don't know where to go to from here other than letting my friend Dave figure it out..