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#1
09-10-2012, 05:41 PM
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1963 silvertone roundie
hey all, yup im back with a question this time focus. this silvertone i have with the 12 clone was never really able to get a really sharp picture focus wise on this set and where it takes the 1v2 i get better focus with the 2av2 rectifier which has been in the set. is there any other possible causes i could look into. when i first got the set the focus coil was alittle burned and the resistor across it was burned open and got a new focus coil compared the ohms with both and were the same so the old one was still good but i used the new one anyway and the focus was really lousy so i put the old one in and it focused better but its not the way it should be. i know if the slug is either to much in or out im not sure, it burns the focus coil. any ideas?
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#2
09-10-2012, 06:03 PM
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you may have wired the focus coil incorrectly. its a coil that shifts phase as you adjust the slug. as the phase shift voltage is added or or subtracted from the primary focus coil. think of it like a variable bucking transformer. You should start by puting the HV prob on the focus output and see if you are getting around 4-5kv and that it varies with the adjustment.
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#4
09-10-2012, 06:42 PM
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it can be a bit confusing with focus coils, esp if they are not the exact replacement. I had one where it would just get from poor to real bad focus with it completely in, I reversed two of the 3 wires and all of a sudden it focused much better and right in the middle of the slug range. Is it a 4 or 5 lug coil?
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#5
09-10-2012, 06:50 PM
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i thought it was 3 or 4 but to this day i dont know why the resistor burned open completly, and the old coil worked better but the new one got really hot and would smell so i wasted no time and changed it to the old one and its been in there since.
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#6
09-10-2012, 06:59 PM
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well if on of the coils opened that may account for a burned resistor. But to really see whats going on you should try and measure the focus voltage and see if it adjust with the slug before starting anything. you need to use a HV meter like the kind used on the CRT anode. I have a simpson 260 with a 5kv scale that I like to use.
Other things that can go wrong with focus IF the voltage is out of whack are the 66meg load resistor, and the 130pf disc cap filter.
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#7
09-10-2012, 07:20 PM
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on this set i think the load resistor was a 42meg and the 130pf cap both i changed and there was no opens in either coils and they check perfect on the ohms. ill be checking that focus voltage and i had got another hv probe tester that works very well not like the last one i had which really gave me lots of problems.
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#9
09-16-2012, 11:48 AM
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well ok heres the deal with the focus thing, i got 5kv and it varies while adjusting however the crt has 24kv and the kine bias is at minimum in order to set the colors i have to raise the bias a touch for the colors to show but if i leave the bias up a touch then put the service switch back to normal the picture is one big blurr. when this happens the hv drops to around 17-18kv which seems as if its being shunted and the hv adjustment is at max put the bias back down all the way its fine great pic and so on but the whites seem to have alittle problem they are not bright and the hv takes a dip with whites. i kind of know this in the beginning that something was not right in the hv section but had left it alone since. the 6bk4 is new, the resistors in the adjustment circuit are fine , hv pot is fine and never found anything else wrong but there is. the boost diode was also changed as well. its like when whites are present the hv dips where there is not enough hv because its not regulating as it should. so this my be why i thought i had a focus issue because on certain screen the focus would seem to change and low hv could do this. so again the back is on and i set it up again and it looks great but something is for sure wrong.
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#10
09-16-2012, 01:01 PM
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maybe a weak HOT. did you check the shunt tube current
 remember how to do that.when you have problems with HV, 1st thing to do is sub in new tubes (damper/HOT/shunt/HV rectifier). clearly you HV is dropping in response to beam current, so either there is too much beam current or not enough HV in reserve. If the pic is dim 1st thing to check besides the brightness and CRT is the video out tube, as the CRT cathodes are directly coupled, a problem there will cause bias issues in the CRT. did you check the HOT drive voltage? if its more neg than it should be then you may have the blanker tube grid resistor trace issue.
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#11
09-16-2012, 01:18 PM
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in the beginning i tried 2 damper tubes 2 6dq5 hot and 3 shunt tubes so i think its ok to say its not those tubes. the overall brightness is bright very good and i tried another video out tube. well i have checked all grounds at the time i had the chassis out unless maybe i missed one trace on the board. what i do have that i cannot get rid of is these retrace type lines and they are color lines and with color down they still show. and no i dont remember how to check shunt tube current or what pins to check on the hot for the drive voltage. so not enough hv could be caused by not enough drive voltage or current?
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#13
09-16-2012, 01:47 PM
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yes i tried a solid state rectifier. the last time i checked the cathode current it was very unstable scene changes was making the reading go up and down so i had lowered it to just under 200 ma around 190 ma and it didnt do it as much. i also pulled the shunt tube cap off and the hv went alittle over 30kv.
Last edited by timmy; 09-16-2012 at 02:12 PM.
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#15
09-16-2012, 06:33 PM
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Quote:
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Linear Mode
