14rp4 substitute

[timmy]

So just putting the resistor across the heater will enable the 14atp4 tube to work. Now I'll have to double check to make certain that the measurements are really close or the same. Well it looks like the 12atp4 overall length is around 3/4 of an inch smaller ,bulb diagonal is the same , screen is 12 1/6 x 9 1/2 as opposed to the the 12rp4 is 12 1/8 x 9 5/8 . How does this look, slight mod maybe to fit the same as the other, what would you decide, chance it ? It is very close.

[dieseljeep]

Originally Posted by timmy

The 14atp4 I wanted to use in place of the 14rp4 and I'm not sure what your saying with the resistor. Are you saying to put in the 17ax4 and 17dq6 in place of the 12dq6 and 12ax4 and then this raises the heater voltage and use a 50 ohm 2 watt resistor between the heater. I'm probably way off here thinking the 17, volt tubes would take more .im missing something on how to get more voltage for the crt . If the physical size is the same as the 14rp4 I could just use a separate heater transformer for the 14atp4 , that should work.

My last entry just cited the tubes that would be in a set that used a 14ATP4 crt. My calculations still show the resistor to be 42 ohm, 3 watt resistor across the 14AT heater.
I just mentioned a 50 ohm, as it's a more common value and will shunt 7.5 volts, kind of a happy medium.
Current in a series circuit is constant and the slight increase will balance out.

[tom.j.fla]

Timmy as far as the ATP4 crt fitment you will have to try it to see, we can't do it for you it's up to you to try it and go from there. Dieseljeep bud you and I, both got the resistance value wrong for the tube in question 8.4 volts not 6.3 volts makes the resistor a 56 ohm not 42 or 24 ohm. 3 watt rating still is fine. Went back and checked the tube specs again and saw the mistake, sorry about that. Tom.J

[timmy]

Originally Posted by tom.j.fla

Timmy as far as the ATP4 crt fitment you will have to try it to see, we can't do it for you it's up to you to try it and go from there. Dieseljeep bud you and I, both got the resistance value wrong for the tube in question 8.4 volts not 6.3 volts makes the resistor a 56 ohm not 42 or 24 ohm. 3 watt rating still is fine. Went back and checked the tube specs again and saw the mistake, sorry about that. Tom.J

Just out of curiosity wouldn't it be safer to just use a separate transformer for the heater and place a resistor in place of the crt to complete the string ?

[tom.j.fla]

Yes you could, finding room on the chassis mite be a bit of trouble though. Finding a transformer with a 8.4 volt at 600ma rating mite be hard though. Remember set makers used shunt resistors all the time till the art of tube making got to the point where their were standardized current draw for all tubes. Tom.J

[dieseljeep]

Originally Posted by timmy

Just out of curiosity wouldn't it be safer to just use a separate transformer for the heater and place a resistor in place of the crt to complete the string ?

A while back, someone wanted to sub a 14R for a 14AT. There, the transformer was the only way to handle that problem, plus a 6.3 volt transformer is a common part.
In that set, there was enough room to mount the transformer.

[timmy]

Originally Posted by dieseljeep

A while back, someone wanted to sub a 14R for a 14AT. There, the transformer was the only way to handle that problem, plus a 6.3 volt transformer is a common part.
In that set, there was enough room to mount the transformer.

Well if I go with a transformer I have to find at least an 8 volt 4 - 8 ma which may be hard to find.

[dieseljeep]

Originally Posted by timmy

Well if I go with a transformer I have to find at least an 8 volt 4 - 8 ma which may be hard to find.

Just follow the proceedure that that everyone seemed to recommend, a 42 to 56 ohm resistor @ 3watts or so.
It's not like you're dealing with a 3KP4.

[timmy]

Originally Posted by dieseljeep

Just follow the proceedure that that everyone seemed to recommend, a 42 to 56 ohm resistor @ 3watts or so.
It's not like you're dealing with a 3KP4.

I have an odd question, how does putting a resistor across the 6.3 heater source give 8.4 v and more ma ?

[timmy]

An odd question, how does placing a resistor across 6.3 v heater source give 8.4 v with higher ma ?
Don't know why it posted twice....

[dieseljeep]

Originally Posted by timmy

An odd question, how does placing a resistor across 6.3 v heater source give 8.4 v with higher ma ?
Don't know why it posted twice....

Using a 450 ma heater in series with 600ma tubes without a shunt resistor, the 450ma heater would receive too much voltage and the 600ma tubes would be starved. You could consider the 450ma heater as the weak link.
Once in a while, an experiment is in order!
When installing the CRT, try various resistor values between 42 and 56 ohms and check the voltage across the heater. Line voltages vary in some areas.
Get the set working properly first, with the original CRT and then address the CRT issue.

[timmy]

Originally Posted by dieseljeep

Using a 450 ma heater in series with 600ma tubes without a shunt resistor, the 450ma heater would receive too much voltage and the 600ma tubes would be starved. You could consider the 450ma heater as the weak link.
Once in a while, an experiment is in order!
When installing the CRT, try various resistor values between 42 and 56 ohms and check the voltage across the heater. Line voltages vary in some areas.
Get the set working properly first, with the original CRT and then address the CRT issue.

So in the end the 14at will be getting 6.3 v or around 8 v . I get the ma but not the voltage. Just had a thought the B&W tube brightiner they increase voltage to but the ma may be low, any thought on these in this case.

[old_coot88]

Originally Posted by timmy

So in the end the 14at will be getting 6.3 v or around 8 v . I get the ma but not the voltage.

A series heater circuit is constant-current.

Parallel heater circuits are constant-voltage

So in a series string, the tubes' heaters have to be rated for a constant current. Therefore different voltages appear across different heaters, leading to oddball voltage designations (e.g., 2AF4, 3CB6, 5GH8, 19AU4, etc. etc.)

In a parallel circuit, the heaters all have the same voltage but some have different currents.

[timmy]

Ok so this admiral is recapped and have sound and close to 9kv for hv and the b+ is around 10 volts less then it should be however I have no raster at all the video tube tests good, any ideas .

[Electronic M]

Is your current tube meant to use an ion trap, and if so is it on and adjusted properly?

What are your gun voltages and what does the service manual say they should be?

Those are the first questions I'd ask myself in your shoes.