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#198
01-17-2015, 04:40 PM
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I got the pop corn out.
Timmy are you sure you have the lugs identified correctly on the focus coil? there should have been a paper with instructions on it. generally the 1st lug clockwise of the red dot is 1, then continue clockwise for the rest. there is generally a ref dot of paint to make sure you have it oriented correctly. then you still should use the paper instructions, they tell which goes to boost, which goes to the 130 pf cap etc... Last edited by DaveWM; 01-17-2015 at 05:36 PM. 
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#199
01-17-2015, 04:47 PM
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when you feel like you have it all correct do the following:
Before power up get the HV prob setup and in place. have the horz out cathode meter in place to read the current have the diddle stick in the eff coil ready to adjust reset the HV pot to mid range. check for any loose wires or solder blobs check the wiring again. have a B+ meter on the B+ 400v test point on the chroma board. make sure all the cap leads (horz out, shunt tube) are in place make sure the convergence board is plugged in make sure the CRT anode is attached and will not fall out from the HV prob. all tubes in sockets, CRT socket attached, kids/pets all accounted for... power on: check B+ should come right up to 400+ maybe spike higher until tubes warm up. watch the horz out cathode current, should rise to about 200ma, if it goes over 210ma unplug set. watch for smoke hopefully you will hear the crackle of the HV and you will be able to set it up correctly with the HV pot now.
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#200
01-17-2015, 05:59 PM
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well let me just say that the blue wire boost is to go on the 11.5 lug, and #1 on the f coil ok , but this is where it was, it was on the 11.5 lug all along its just that it was not the bottom wire so i really cant move anything because i can move the wire to the bottom lug but that was the 10.5 on the #2 f coil lug. you said it was to go to the lug with the higher ohms and this is what i had explained i think on 2 pages back. and yes i know i was going to take all those precautions. the f coil is numbers 1234 and the miller paper shows it but my coil here has no mark except the mount key so i use the #4 to identify the proper sequence in numbers along with the sams , shows the shape of the lugs on the coil and #4 lug.i am not ignorant but i really am confused.
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#202
01-17-2015, 06:06 PM
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Quote:
Quote:
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#203
01-17-2015, 06:58 PM
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ok dave i have to run out yet again so i am going to confirm any of my mistakes and i will get back to you tomorrow. i see your quote from me so i am going to test the lugs again and get it right this time as we really got far ahead of things and i guess it messed me up,lol,lol. ill send you a PM with the number.
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#204
01-18-2015, 05:42 PM
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Timmy and I have been in contact over the phone.
I believe he has the flyback hooked up right. A test was done with a known good 6BK4 as follows: bad set 6BK4 installed in known working set, Known working set exhibits the same problems so the 6BK4 is causing the problem Known good 6BK4 is installed in Bad set, 6BK4 quickly appears to short out around the filament leads. Tube is tested by retrying in known working set, confirmed prior good tube is toast. So we concluded the regulator tube is the issue AND the bad set seems to be creating bad tubes from good tubes. http://scottbecker.net/tube/sheets/137/6/6BK4.pdf Timmy is going to check the HK voltage potential to see if it is exceeding 225v per the data sheet. I am thinking a problem with the voltage divider resistors (180k/150k) off the B+ that is used to float the shunt heater upwards to prevent insulation breakdown around the heater. Timmy will 1st check the known working set pins 1 and 2 of the 6bk4 socket (HK) voltage and then compare to the bad set. I advised him to simply disable the HV for now by pulling the horz out while testing. remove the 6bk4 and read the voltages right a the socket. I would also like Timmy to check voltage pin 1 to ground (shunt cathode) and pin 2 to ground (shunt filament). again the difference in the two voltages should be less than 225vdc If there is a problem, I would guess the 180k side of the voltage divider (filament to B+) may have opened up or drifted up dropping the DC voltage on the filament. Last edited by DaveWM; 01-18-2015 at 06:15 PM.
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#205
01-18-2015, 06:28 PM
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Very good thinking..... But with 400V on the cathode I believe he said was there,
or it was on the grid, I bet it's the second resistor, R124 150K to ground... open really pushing the potential up.... Yah I downloaded that tube spec sheet trying to see what it's operating parameters are, and any notes on breakdown.... Didn't get lucky... Good work, be happy to see this thread finished and locked forever.... Hope you get good news from him soon ! ! So how long does it take for that tv to kill one of those reg. tubes....? .
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Yes you can call me "Squirrel boy" Last edited by Username1; 01-18-2015 at 06:35 PM.
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#206
01-18-2015, 06:35 PM
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the K is about +400v so if the heater drops to less than 175v he will have trouble. If
the bottom of the divider opens, the heater would go to +400v, 0 difference vs max of 225. I guess it could go slightly positive (10-15v) with respect to the cathode ("not recommended to go positive" per data sheet) since the voltage divider begins right at the 405v supply (before the choke and vert out trans where the K voltage comes from, which puts it about 15v lower IIRC) but anyway its something to check that has not been check yet, so fingers crossed! Last edited by DaveWM; 01-18-2015 at 06:44 PM.
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#207
01-18-2015, 06:42 PM
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Ahh. So you think the source resistor is opening, taking away that reduced potential
needed to prevent heater cathode breakdown.... And once that happens you think that is not effecting the cathode voltage ??? in a downward direction from whatever short develops Heater to Cathode.... Interesting.... Oh-Ya My fingers are crossed.... Poor guy a couple-a years chasing this problem.... I wonder how many times this cropped up in the field.... and how long it took other people to find it.... .
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Yes you can call me "Squirrel boy"
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#209
01-18-2015, 06:47 PM
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Quote:
IF it turns out to be the problem you can bet I will be checking those two resistors out regularly, darn 6BK4's are not cheap.
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#210
01-18-2015, 06:53 PM
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My thinking is this
New tube goes in, gets smoked enough to drop the K down due to leakage just enough to screw up bias, Thinks tube must be good since it brand new, etc... I had Timmy pull the back off a known good set to observe the look of a functioning tube (how the filament changes intensity as it regulates). I warned him of the X ray exposure so not to do this long just see how it should look when working. Needless the say the bad set tube did not behave the way the good tube set worked.
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Linear Mode
