RCA 14-vt-8157
 

I recently bought this tv phono combo and had some questions about the crt that is in it. It has a replacement crt labeled 14atp4 in it but when I would test it at 8.4 volts it showed h/k short, at 6.3 v it tests as new. Diesel Jeep suggested it was 600MA tube, (should be 450 ma), so today I tested again with amp meter hooked up. At 4.2 volts it draws 450ma but still tests very strong, and at 6.3 volts it draws 600ma. So will this tube work in this series string tv as is or do I need to add seperate filament transformer for crt? Do you think tube is really 14rp4?
PS: Diesel Jeep, you were spot-on from the start on this Thanks for your help.
This a continuation of this thread
http://videokarma.org/showthread.php?t=260496

The 14ATP4 is listed as a 8.4 volt heater but it may have been rebuilt with a 6.3 volt gun.

Since it shows a short at 8.4 that would suggest that the heater is overstressed at that voltage, running it like that will kill the tube in no time. I would go with a 6.3 heater transformer to play it safe. Of course you will have to add some resistance to the heater string to make up for the missing CRT.

I ran into this issue with my Sonora portable: http://www.videokarma.org/showthread.php?t=260202

It should have a 8.4vac 450ma CRT, but someone stuck a 6.3vac 600ma CRT in it. It does work, but it takes quite a while for an image to appear because it's being starved of heater current. I'd go with a transformer as Eric suggested if possible.

I wonder if a brightener with the heater circuit wired in reverse would work?...

I would try a series brightener, as-is. They are an auto-transformer, type design. It just might give the heater, the small increase in voltage, to make a difference. :scratch2:

Thanks everyone,
I will recap and then try a brightener. If thats not satisfactory then I will go with the transformer.
I have a brightener that say's for use on 110 degree tubes (series filament) what happens when you use it on a 90 degree tube?

Careful - brighteners boost the voltage and you want to reduce it while increasing the current. That's why Tom suggested wiring it in reverse. I'm not sure why they would specify 110 degrees except maybe to indicate the base type ?

But,wouldn't the voltage drop across the filament only go high enough to get the tube to draw the same current as all other tubes? (about 4.2 volts)

continuation of this thread http://videokarma.org/showthread.php?t=260496
 

continuation of this thread
http://videokarma.org/showthread.php?t=260496
I have it recapped and I wired in a 6.3 volt transformer for the crt and installed 20 ohms to complete filament string. Everything is fine exept for the vertical section seems to be running at 120 cycles as I have two images, one above the other on screen, I am checking suspect resistors but hav'nt found a problem yet.
Are there any known problems with ceramic disc capacitors from this vintage sets? Diesel Jeep, Any of your notes on your Sams vertical section give me any clues? Thanks

Every time i've run into this situation it's been a resistor drifted way out of spec or I installed the wrong capacitor in the circuit, .01 instead of a .001 for instance.
I would look closely at the caps around the Vertical oscillator tube.

I'll look at the Sams and report a little later. :scratch2:

The Sams notes show the following components: C84, C83, C80, C90, C79, C85, C89, C78, C86. The notes also say that, this was a thermal problem as well.
I don't know the tech that entered these notes, but they did say that the ceramic caps, were suspect, as well.
Those sets seemed to be a hot-box design and was subject to thermal related problems.

Thanks guys, I worked at it awhile yesterday, double checked caps on curcuit board, and tested resistors, I still havn't found the problem but i'll keep working at it.
Kevin, If that offer still holds I would sure appreciate it. Schematic, and if they have a resistance chart and voltage chart I would be grateful. sams 396-3
Thanks, Paul
paul.knaack@yahoo.com