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-   -   Problems with RCA TV 21-S-548 KCS88NX (http://www.videokarma.org/showthread.php?t=272685)

kramden66 03-29-2020 04:24 PM

Problems with RCA TV 21-S-548 KCS88NX
 
3 Attachment(s)
Recapped and running but issues are - The image seems too zoomed in , too over scanned ( see pics ) is this a yoke issue ?
tried moving yoke a little back off the neck and it didnt seem to do anything.

Second there is smear in the image as can be seen in the picture of the stars.

Third the vertical is too stretched , you can stretch it further but not shrink it , the lin can create a small fold over at the bottom of the screen , the vert hold can be rotated to create multiple image where you can see the top at the bottom and bottom at top .... recapped , resistors checked , vert out and vert mult tubes changed , only slight improvement with vert out tube changed.
vert out transformer reads proper ohms.

opinions on how to tackle this ?

sams set 279 folder 13

old_tv_nut 03-29-2020 06:47 PM

Moving the yoke back would make the image bigger, not smaller.

Maybe the high voltage is low? Don't know.

kramden66 03-29-2020 08:28 PM

if high voltage too low wouldn't the vertical not be enough ?
maybe voltage is too high >? let me try the variac

kramden66 03-29-2020 10:29 PM

well if you reduce the voltage the picture looks like it zooms back , if you go down enough the vertical goes into a line .... perhaps too much voltage , tough to measure voltages because this is one of those sets where the crt stays in the cabinet

old_tv_nut 03-30-2020 01:06 AM

Don't confuse B+ voltage and high voltage.
Check the B+. If it's OK, the sweep currents should be OK (because you have shown the overscan is in both vertical and horizontal). But if the high voltage is low, sweep width and height will both be too big.

kramden66 03-30-2020 12:10 PM

Ok I have to figure out what the voltage should be and where to tap in to get the voltage readings

kramden66 04-12-2020 01:23 AM

ok back to this beast .. the votages after the 5u4 i get 295v when it should be 280v , 285v when it should be 270v , so its running a little high but not enough to knock things out of whack

vert out voltages are close its the vert mult that is off pin 6 should be 155v i get 92v , pin 7 should be -58v i get -37v

i will check the anode voltage to se what i get and post that.

Now the crt is a replacement , no number or make anywhere , is it possible the crt is not a proper replacement and the yoke needs to be changed ?
Also even if thats the case the vertical issue needs to be taken care of , you cant make a letter box image if you wanted to and as stated the 155v is 92v and the -58v is -37v and that could be a reason.
any suggestions ?

kramden66 04-12-2020 01:37 AM

i'm getting about 16kv on the anode when the sams says 12.5kv , so it is high , how do i get it down ? is it a horz out issue?
it uses a 6BQ6 , perhaps if i put a 6BG6 in ?
This may explain the ozone smell , well i think theres one

kramden66 04-12-2020 02:19 AM

Also need to add hot pin 6 is 180v should be 150v , pin 5 23v should be 17v pin 8 12v should be 8v


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