The internal document from the lead engineer describes the chassis as having "one 227, six 224's and two pentodes". All six of the 224's are specifically called out, first detector, 1st IF, second detector, 1st amp, sync amp and picture amp. The only tubes not specified are the 2nd and 3rd IF's. This coupled with the extra contacts on those two, and only those two sockets verifies them as space charge pentodes. Unfortunately no other mention of the tubes has been found.
Looking at the specs for the P1, this is no doubt the type of tube used here.


For whatever reason they actually used the negative resistance of the 224's for the scan oscillators which makes no sense as the lab work prior to this set used gas thyratrons and the the field test sets after this one used blocking oscillators. Why in heck did they use finicky dynatrons oscillators?


I never noticed this. Which graph was this? (Maybe someone was really optimistic about the performance )

Dynatron oscillators, using pentagrid tubes, (known as phantastrons)
make good frequency dividers, and can be coupled with simple r/c
circuits for count ratios . TV needed co-related field and frame frequencies to work.

The HP 525b frequency counters used that divider, and it worked
very well...(when it worked )

In NTSC 525 line (BW) TV the 15750 Hz horizontal and 60 Hz vertical derives
from the same clock. (one nifty effect is when 60 Hz power line leaks into
the video in TV sets, you see a floating ghost bar floating up the screen.

That is because the TV 60 Hz, isn't phase locked to the power line.
(also the power line 60 Hz isn't locked, it is shifted to move power
around the grid)

I would love to see the schematic of the old RCA sync system)

Steve
The dynatron's in this set are used as the fundamental oscillators for the line and frame scan not as dividers. They are very unstable and only about 1 in 10 NOS tubes even works reliably. It doesn't make much sense why they chose this oscillator type as the negative resistance region on the 224 is not characterized or repeatable between tubes.

I just looked through the IRE papers again and can't find any incorrectly labeled graphs. Which one did you find in error?

Darryl

Dynatron oscillators have been used for years (long ago) as signal generators.
they used the 222 battery tetrode.

A 224 of any ilk should be predictable providing the screen and plate voltages meet
the criteria for oscillation, at least if the have a reactive plate load.

Can you show or point to the circuit for your project ?



AA Ghirardi Radio Physics Course 2nd ed. 1932

Getting a little off topic, but dynatron oscillators using uncharacterized parameters running at 24Hz are not predictable. Some tubes oscillate, some don't. Some oscillate way to high out of range, some way to low. This using all NOS tubes. It seems this was a terrible choice for oscillators when other types were well established.

The graph is not terribly readable but is marked 3.70 to 4.30 MHz.

24 Hz would imply large values of capacitor and/or inductors. The clearer
graph shows the decimal, however all the other graphs were labeled in kHz.

After 80 years, would the Q of the coil and the D of the capacitors be intact ?


The would explain failure to start oscillating.



Of course if the coil is iron core, maybe it needs degaussing.

Can you show the circuit diagram of the system ?

Other strange properties of old tubes may be measured by
the att'd ASTM proc below.