silvertone roundie

[ctc17]

1.5 ma and correct cathode current would indicate the hv is working ok. correct screen voltage is another really good indicator the hv is working right.

[timmy]

Originally Posted by ctc17

1.5 ma and correct cathode current would indicate the hv is working ok. correct screen voltage is another really good indicator the hv is working right.

but the voltages at the 12by7a are not right.

[ctc17]

The problem is the brightness control has way to much range and is over driving the video out.
Check r62 r64 and verify the brightness pot is not open

[timmy]

ok well i will close this thread by saying i am done with this silvertone as i just lowered the brightness readjusted the rgb drives and no more blooming with the bias up alittle to account for the weakest gun,RED and the whites are white now and no hv drop with whites. so i checked the brightness control pot and its right on at 250k and r62 and r64 both good as well as other resistors around the video output tube so in finding nothing else wrong here all i really did was lower the bright a touch so if this is what it took to improve what was wrong here well then i am going to leave it and take advantage of the fact that these sets had 10-20 or maybe 30% built in so if i am using a 10% leeway here well thats why they had this high of percentage, for errors because these sets were far from perfect so im happy with it now. well what more can i say,lol,lol...

[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.

[miniman82]

Remember also that these old sets will never be as bright as a modern one, I find that people overadvance the brightness control on a regular basis then wonder why the picture blows out. A weak tube will make things worse, so if you don't plan to get a new CRT I'd live with the reduced brightness.

[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.

[timmy]

ok, sounds like a possibility and i will get to it but i am certain in the beginning i went nuts checking everything and i do remember that resistor, its red and im sure i checked that one also. thats something like a 3-5 watt resistor. thanks davewm for that info, ill get on it. i just took a look at the schematic and there is 2- 5600 ohm resistors and a 2700 ohm so ill just chect them all as they are power resistors.

[DaveWM]

I am not sure you can test it in the circuit, so the best way to check is the voltage test at pin 7.