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 Post subject: Re: Was there ever a 2.5V Pentode with UY base?
PostPosted: May Tue 28, 2019 9:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 694
Location: 48314
radiotechnician wrote:
I read the IRE references, and are convinced they used 24-A (224) tubes,
not 235. They were doing some groundbreaking work then. I don't think
it was realized that those tubes could operate at 60 mHz.

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.

radiotechnician wrote:
The tetrode circuits would have to work well outside the dynatron kink
zones for the tubes. Had they used 235 tubes, they would mentioned what
transconductance they chose, and perhaps if it varied, how the IF response
curve would change.

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?

radiotechnician wrote:
As is, the paper has an error in one of the graphs, megahertz instead of kilohertz
Nothing in that setup could have worked at 400 mHz.

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


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 Post subject: Re: Was there ever a 2.5V Pentode with UY base?
PostPosted: May Wed 29, 2019 3:15 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 11715
Location: Powell River BC Canada
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 :D )

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)

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VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
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 Post subject: Re: Was there ever a 2.5V Pentode with UY base?
PostPosted: May Wed 29, 2019 3:34 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 694
Location: 48314
radiotechnician wrote:
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 :D )

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


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 Post subject: Re: Was there ever a 2.5V Pentode with UY base?
PostPosted: May Wed 29, 2019 5:21 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 11715
Location: Powell River BC Canada
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 ?

Attachment:
RCA     this one.JPG
RCA this one.JPG [ 93.78 KiB | Viewed 162 times ]
Attachment:
Ghirardi  dynatron 222.jpg
Ghirardi dynatron 222.jpg [ 427.63 KiB | Viewed 161 times ]
Attachment:
Ghirardi dynatron ii.jpg
Ghirardi dynatron ii.jpg [ 464.93 KiB | Viewed 161 times ]


AA Ghirardi Radio Physics Course 2nd ed. 1932

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


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 Post subject: Re: Was there ever a 2.5V Pentode with UY base?
PostPosted: May Wed 29, 2019 1:26 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 694
Location: 48314
radiotechnician wrote:
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.

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.

Attachment:
graph.jpg
graph.jpg [ 281.67 KiB | Viewed 158 times ]


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 Post subject: Re: Was there ever a 2.5V Pentode with UY base?
PostPosted: May Wed 29, 2019 10:38 pm 
Member

Joined: Sep Thu 23, 2010 6:37 am
Posts: 11715
Location: Powell River BC Canada
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.

Attachment:
Dynatron de Terman, F E  4th ed  1955.jpg
Dynatron de Terman, F E 4th ed 1955.jpg [ 353.92 KiB | Viewed 142 times ]


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.
Attachment:
Thermionic i.jpg
Thermionic i.jpg [ 370.74 KiB | Viewed 142 times ]
Attachment:
Thermionic ii.jpg
Thermionic ii.jpg [ 124.46 KiB | Viewed 142 times ]

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


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