silvertone roundie

[timmy]

contrast control works fine, its at half. the problem here is hv not regulating and that it does seem that the hv is being loaded down. another video out tube i dont think will help but change little. the color lines i adjust to see then back off til just gone. and no i didnt check anything around the service switch. i think the sams did say something as to where the controls should be and i did what it said.

[DaveWM]

Why do you say its not regulating, I thought you said the shunt current changed with the brightness and was between .5 and 1.5 with a dark to bright raster and the HV held to 23-24kv all signs that HV regulation is working as it should.

Now you may indeed have a over load that exceeds the ability of the HV to supply current at excessive beam current in the CRT, but this is unrelated to HV regulation. The shunt can only regulate within a beam current operating range, go beyond that and its NOT a regulation problem, rather its a load problem, You keep saying it like those can't be separated. you could confirm this by observing the shunt current when the blooming happens, the current should drop to 0 as the KV drops to 19kv. this would indicate the regulation is working as designed and you are simply overloading.

My guess is you are simply over driving the CRT to make up for a brightness deficiency real or imagined. there could be an issue with the service switch that may be making the setup not work properly, but that can be worked around, not all set had setup switches you just do it by eye with a live signal.

I am sure you will suddenly have the solution and it will all be fine.

[DaveWM]

Originally Posted by DaveWM

My guess is you are simply over driving the CRT to make up for a brightness deficiency real or imagined. there could be an issue with the service switch that may be making the setup not work properly, but that can be worked around, not all set had setup switches you just do it by eye with a live signal.

I am sure you will suddenly have the solution and it will all be fine.

See above. from page 5 some 40 post ago.

Talked to CTC-17 says he talked to you about too much brightness range, seems like something that could be figured out if you stick with that.

[timmy]

Originally Posted by DaveWM

See above. from page 5 some 40 post ago.

Talked to CTC-17 says he talked to you about too much brightness range, seems like something that could be figured out if you stick with that.

yes it does seem now that the brightness control is driving alittle harder then it should and yes i can leave the bright reduced alittle but as ctc17 said when the sets were made no one would have wanted a new tv set that had to have the brightness lowered to fix other things. i would have thought the control was bad but it was not and the resistors as well are good. its not me overdriving anything to try to get a brighter picture, brightness was not the issue, hv and white colors and crt bias was so all these things are affected. so ill leave it for now but i will keep this brightness issue on the back burner should anything related to that crop up.

[DaveWM]

check the voltage at the plate of the 12BY7 with the service switch set to service.

[timmy]

Originally Posted by DaveWM

check the voltage at the plate of the 12BY7 with the service switch set to service.

ok, when i get a chance to get the back off again ill look in to that voltage at the plate. would you know off hand which pin is the plate otherwise ill look it up ?

[DaveWM]

Pin 7. What you are checking for is to see if the plate voltage drops to zero when in the service mode. I was doing some reading on RCA's and if this set has the same video out circuit, then it may have the same issue. If the 5.6k power resistor opens up (its on the service switch) you will lose plate voltage to the video out tube while in the service mode. The symptoms of an open resistor is very critical brightness setting.