silvertone roundie

[timmy]

i dont know what this means but bwhen i raise the bias the rect tube filiment dims and the whole screen goes blurry and the hv drops way down.

[ctc17]

Ok I will look when I get home.

[ctc17]

Originally Posted by timmy

i dont know what this means but bwhen i raise the bias the rect tube filiment dims and the whole screen goes blurry and the hv drops way down.

You are overloading the HV or there is lack of HV capacity. What is the screen voltage on the HOT and what should it be?

[stromberg6]

Hmm... Gassy CRT? I never had that symptom. Be interesting to find out what it's about.

[timmy]

screen volts on the hot ill need alittle help there where to measure but the rgb screen drives are to be 620-680 volts im getting around 600volts bg drives are to be 290v im getting 250-280 volts there. i also pulled the hot and measured the cap volts and thats 415v. horiz tube 6fq7 pin 6 is 280 volts. focus volts are 4500kv.

[ctc17]

No No. the screen voltage on the horizontal output tube. Its usually around 190v. Its usually on the right side of the tube on the sams, opposite the grid which should be around -45v.

stromberg6; this is a fairly common problem on these old color sets. If there is excessive drive to the horizontal output tube or a bad capacitor, even a defective focus control causing the HV to run inefficiently it wont be able to keep up.
Kinda like if a car has a restricted exhaust it falls on its face when trying to climb a hill.
These can be difficult problems to diagnose because its half way working.

Some of the confusion with this thread is a problem thats related to the ctc16 chassis only. On the 16 there is a very thin trace on the edge of the board that fails and causes excessive drive to the output and results in lack of capacity.

[timmy]

ill try to get to those terminals the sams shows -50v and the other 140v. i did check cathode current its at 200ma and the hot is not red plating. ill check those voltages.

[timmy]

ok the hot screen volts sams shows -50v and i get -55.9v and the other sams shows 140v i get 140v. i had changed all the red caps in and around the horiz and many more.

[ctc17]

55 is kinda high. I bet once its fixed it will be -50 @220ma and will work right. Yes 5 volts can make that much of a difference. Hang out till I can get home and look at the sams.

[timmy]

Originally Posted by ctc17

55 is kinda high. I bet once its fixed it will be -50 @220ma and will work right. Yes 5 volts can make that much of a difference. Hang out till I can get home and look at the sams.

i checked these voltages with the set running normal i just put 2 wires in the socket and put the tube back in and waited about a minute then i checked.

[stromberg6]

Originally Posted by ctc17

No No. the screen voltage on the horizontal output tube. Its usually around 190v. Its usually on the right side of the tube on the sams, opposite the grid which should be around -45v.

stromberg6; this is a fairly common problem on these old color sets. If there is excessive drive to the horizontal output tube or a bad capacitor, even a defective focus control causing the HV to run inefficiently it wont be able to keep up.
Kinda like if a car has a restricted exhaust it falls on its face when trying to climb a hill.
These can be difficult problems to diagnose because its half way working.

Some of the confusion with this thread is a problem thats related to the ctc16 chassis only. On the 16 there is a very thin trace on the edge of the board that fails and causes excessive drive to the output and results in lack of capacity.

Thanks for the explanation. So many things to go screwy in a horizontal output system that are related. Saving the comments for future reference. Thanks!

[ctc17]

Originally Posted by stromberg6

Thanks for the explanation. So many things to go screwy in a horizontal output system that are related. Saving the comments for future reference. Thanks!

Yea exactly. Dont mention gassy crt to timmy or he will be at the local pharmacy looking for a fix.
Lets start by verifying the HV system has enough capacity.

[ctc17]

Ok lets fix this thing....
The first thing I will say is the 390k resistor has nothing to do with it on this set. Its not even tied together like that. The thing calls for 200ma, if thats what you have and the screen is 140v I would wonder if you got the bias and the screens cranked up way to high. Check the HV reg current (it has a jumper) and see if you are getting the 1ma with a dark screen.

[timmy]

Originally Posted by ctc17

Ok lets fix this thing....
The first thing I will say is the 390k resistor has nothing to do with it on this set. Its not even tied together like that. The thing calls for 200ma, if thats what you have and the screen is 140v I would wonder if you got the bias and the screens cranked up way to high. Check the HV reg current (it has a jumper) and see if you are getting the 1ma with a dark screen.

ok, the crt bias is down ccw all the way the R G B drives are not even a quarter up they are very low, and the G B drives as well are really low. because i know if they are to high then sometimes you get the lines running across the screen like i have now faint but i see them and they each are a color.there are only 2 sets of lines running left to right and fades toward the middle. could you tell me where or what to break to check this hv reg current with the meter? would this be under the chassis or could i get to checking it behind the 6bk4. as far as a gassy crt i have looked in the dark for the dreaded glow of death in the neck and never seen any. as far as the crt testing, on the bk440 tester at 5v after a minute the needle bearly makes it close to the 200 mark which 200 reading or more is good. at 6.3v the needle just makes it over the 200 mark. at the color setting next to 6.3v it may be 7v i dont know it shows very good so i really dont know if the 6.3 reading would infact be good or if the crt is tired well then it is what it is if everything else checks out ok. the jumper in the sams for hv reg current is that jumper closed or is it opened all the time? the reason i ask is that jumper if i remember correctly was under the chassis and i think it was closed by means of a component where on the tie strap one leg was long and was tied together that way and i may have opened it thinking it was not to be closed and that it was open to put a meter across.should this spot be closed? i will look under to see if i had left it opened or closed. because i remember open or closed the set worked. ok 1ma bright down.

[DaveWM]

IF for some reason the jumper was removed and left off, then you will have NO hv regulation, and you may have too high HV since the idea is the shunt tube should conduct at all times (bright and dark screen). How much current it shunts depends on the HV pot setting AND the overall load on the HV system.