Restoring a 1963 Admiral ctc-12 clone

[kramden66]

I've replaced a couple film caps even though they are not leaky and might replace a couple others to see if there is a change , sad thing is it just happened , wasn't like this when I first got it running , I replaced all the electrolytics , also got a good 12BY7 , my previous had very low emissions so I'm hoping it too wlll correct things or maybe was the culpret.

I still wonder should I check all those resistor looking capacitors on the if board or at least the ones near the 6AW8 ? if yes and one is bad a mica cap will work there as long as it is the same picofarads value ?

I really want to put the thing back together and watch it

mike

[kramden66]

Well the new 12BY7 helped a little but it still has the ghost issue and a smearing in white from the ghosting almost looks like ice in the white objects , the ghosting doesn't change when the tuner is adjusted but the smear caused by the ghost changes when tuned back too far and the color wont work ( pictures are to show ghosts and the smear and the changing of the smear ) get no color i , I jumped the delay line and saw no change or no effect , I guess you have to disconnect one end , I accidently disconnected the ground to the delay line , things looked odd and there was no brightness control , I found the cause of the bright green line when in service mode - too much kine bias.
I also checked the hot cathode with a .47 cap hooked to each end of the meter wires, I see 190 ma

mike

[timmy]

just alittle to add here, maybe a cap or resistor within the yoke as i had a simillar problem with a motorola and it was a resistor that was bad and thinking it may have been something with the fly i had changed it but didnt help. my silvertone has that ghost like image on some scenes but not all and i have a hunch it may be fly related as i cannot get a perfect focus because the focus voltage is alittle low and the focus coil had heated up at some point and i think it may have done little damage to the fly in some way. but we keep on keepin on....

[kramden66]

focus is fine , no overheating of the focus control or fly , perhaps the if needs alignment or one or more of those resistor looking capacitors on the if board is at fault ?
be a real pain to pull them to check them

mike

[timmy]

well when i had some issues with sets i would use the stick on those cans and mark where i started and turn them one by one to see if i got an improvement and if not i would return it back where it was. i have had luck doing this in the past as one may be off just a bit . but if you do this remember to mark where you start first to put it back if you have to. but if the problem is corrected then leave it. just to avoid a whole alighnment procedure.

[kramden66]

if you disconnect the delay line and jump it directly you get weak sync , no color , and its is jittery , I then tried a 2 ohm resistor and a 40 ohm resistor hooked to the delay line to see if the ghost and ice changed, it didn't , so my guess is the if section may need a tune up or maybe theres a cap or resistor in the yoke that's not right , or one of those capacitors that look like a resistor is at fault , I decided to give up and use it as is , its not unwatchable butit would be nice to have it a tad better , the cathode current on the horz out is 200ma , I had to turn the hv up all the way because if you don't the horz gets too skinny , focus is effected and circles are not circles , the anode is running 22kv and with brightness down around 22.5kv , the fly is not getting hot or warm, the convergence is very good , it does show some red around objects but that's with the color on , if you turn off the color they are gone so its not convergence , the red around objects will go away if you tune back but then the image is not as clear and you have to crank the color control high to get colors , again this suggests if tune up might benefit the set , can't complain about it because the colors are right and the image pretty sharp.
oh yeah I tried the stick idea and was careful, it made no change to the ghost , there is one that wont turn , its frozen , not sure which it is without looking at the schematic , just thought I'd add that

[Tubejunke]

Originally Posted by kramden66

I also checked the hot cathode with a .47 cap hooked to each end of the meter wires, I see 190 ma

mike

So, is this the final verdict on checking that current. I'm curious because I am getting ready to put my new horizontal linearity coil in my Zenith and I want to measure the cathode current. I have never read about putting a cap on each meter lead.

[timmy]

.47 across the leads.

[old_coot88]

TJ and Timmy:

Are you talking about an analog or digital meter?

If analog (mechanical movement), no cap whatsoever is needed.

If digital (and I have never attempted to use a digital milliameter in that application AND WOULD NEVER), put as large a cap as possible across it, preferably several thousand mf.
This is because the waveform is complex and spikey and the meter will go nuts on that unfiltered waveform.
Considering that the meter presents a very low circuit impedance, a very large capacitance would be needed to attempt to smooth it. Even then i would not trust it.

Lacking an analog meter, i would use a #44 light bulb to accurately 'dip' the cathode current (as discussed in another thread).

[kramden66]

with or without a .47 capacitor across the leads my digital multimeter is not erratic and shows a reading , I have it at 200ma and as it runs you may see it say 199 for a minute then back to 200 and while running it may show 199 again but eventually will show 200ma , the capacitor across the leads is mentioned in the procedure in the sams how to test the cathode current, and I should metion the meter has that separate 10a for the red lead to plug into , that is how it is used to measure ma , if one tries with it in the standard input that reads ohms and volts it will not give a proper reading.

[miniman82]

I never saw an issue reading HOT current either, with or without the cap. I insert a 10-ohm resistor now though, and measure voltage instead of current.

[Tubejunke]

Just the way it was worded sounded like one connected in series with each lead as opposed to one in parallel with the two leads. I think I will go with the mighty Simpson analog meter. No real reason; I just like analog meters, but I firmly believe that you could do the job with a digital meter and get a rock steady reading.

[old_coot88]

Originally Posted by Tubejunke

...I think I will go with the mighty Simpson analog meter. No real reason; I just like analog meters,..

You're speakin' of the Simpson 260, right? That's the only meter i ever used for general servicing for 30+ years (except for the rare occasion when a VTVM was needed for probing some high impedance circuit).

...but I firmly believe that you could do the job with a digital meter and get a rock steady reading.

You might be able to run red lights and stop signs for a while, too. I would never use a digital (don't even own one) for anything but pure DC, clean sinewave AC, or ohms.

[timmy]

and yes i was talking about the cap with a digital vom. and of course i have yet another problem with this ctc12 clone, in the service mode and all the drives down counter clock i have a blue line across the screen and the crt bias down as well, counter clock. any ideas, maybe a bad bias pot , i dont know but would like an idea befor pulling the chassis. although i do use an analog meter now for cathode current

[kramden66]

I'm just guessing but check the bias pot , any associated resistors , also check the blue drive and associated resistors and then if all else checks try the blue screen , also if that fails make sure the crt socket has clean contacts but start with the bias and work from there , if old coot has better ideas from experience I'm sure he will pipe in.

old coot any idea whats causing the ghost in my set ?
mike