Thomas
:So..........what is the difference between a 50B5 and a 50C5? They both function exactly the same. Their only real difference is pin layout. Why were they both developed?
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:Thomas
Hi Thomas,
I barely remember reading something about this years ago. It seems UL and some other safety concerns thought there was a safety issue with the 50B5. In the 50B5 the plate pin (5) is next to one of the filament pins (4). I guess they thought there was the possibility of a short between socket pins 4 & 5 or short/flashover between the tube pins inside the tube possibly causing a safety hazard. Thus a redesign resulting in the 50C5. Maybe someone else on here has a remembery better than their forgettery and can enlighten us more.
Radiodoc
Also, the worst thing I've seen in common practice besides a live chassis is where the RF interference supression condenser is connected directly across the line cord instead of after the switch. This means that it's always on. If it shorts, you may not be near the radio, whereas if it was after the switch, you'd most likely be near the radio. I've had plenty of these short out and sizzle, too. I always wire new ones after the switch. Another thing they do when they're always on is they draw unnecessary current. You can see this when you slowly plug in a radio and the plug sparks even though the radio is off. Modern television and radio manufacturers have mastered unnecessary current consumption, though, so the condenser is pale in comparison. The lovely "stand-by" feature is a terrible one in this age of fuel and energy conservation (so-called....kind of like the gay '90s of the 19th century).
Anyway, always interesting to figure this stuff out. Lord help you if you put the wrong tube in the wrong socket....say you mistake a 50B5 for a 50C5, etc. Lots of smoke!
Thomas
:Interesting. I'm amazed at what UL lets pass or what they won't let pass. If a flashover is possible, then I guess it's a good idea to eliminate the possibility. If something did short, though, I'd think it'd blow the cathode strip in the rectifier or the output transformer, or the fuse resistor, if one is present. We've all had these items blow for other reasons so common to tube radios.
:
:Also, the worst thing I've seen in common practice besides a live chassis is where the RF interference supression condenser is connected directly across the line cord instead of after the switch. This means that it's always on. If it shorts, you may not be near the radio, whereas if it was after the switch, you'd most likely be near the radio. I've had plenty of these short out and sizzle, too. I always wire new ones after the switch. Another thing they do when they're always on is they draw unnecessary current. You can see this when you slowly plug in a radio and the plug sparks even though the radio is off. Modern television and radio manufacturers have mastered unnecessary current consumption, though, so the condenser is pale in comparison. The lovely "stand-by" feature is a terrible one in this age of fuel and energy conservation (so-called....kind of like the gay '90s of the 19th century).
:
:Anyway, always interesting to figure this stuff out. Lord help you if you put the wrong tube in the wrong socket....say you mistake a 50B5 for a 50C5, etc. Lots of smoke!
:
:Thomas
Sir Thomas, and the Nostalgia Crew,et al:
Your comments on AC line capacitor plus “ Lord”, keyed me in on adjunct thoughts of a remembered situation in the past…antique?…right!
Plus, it does concern the venured All American 5.
It seems like it was back at the initial time into the design transition of solid state circuitry into AM table model radios. Now with me being
of the age of just transitioning out of being a teenager that would leave my widowed aunt being well on towards her “golden years”. She
naturally had a block of her younger years when radio was IT, as fare of prime entertainment in a rural setting.
The ONE thing that TOTALLY amazed her, above all, was the fact that new radios that were solid state, came on the INSTANT that
they were turned on.
WOW…I’ll just bet that cumulatively…that she has spent a whole week of her lifetime…. to date….. just waiting for tube radios to warm
up
Needless to say…..her being my favorite (widowed) auntie….Jack Armstrong….All American Boy / Hero…(moi)…..thinks about the
situation and then I offer to make her existing radio just like the new solid state ones..INSTANT ON. Her immediate response was…
NO…. YOU DON’T MEAN IT !......At that instance she would have aptly considered me to be able to walk on a sea of water to fulfill
that task…alas no, (but I do frequently pass water !)
So I take her radio in hand with me and later put it upon the workbench and disassemble it and take a silicon power rectifier diode and
install it across the power switch, polarity being such that its cathode will be towards the AC line. Thereby, when then plugged in, negative
rectified nodes will pass thru and power up the filament string at a half power, in a very dull red glow, “prewarmed” up state. When the radio
switch is turned, only then is full ac power passed thru to the power rectifier as well as full filament string power then being received.
The end effect being …..BAMMMMM……instant on sound..
All was well, and even forgotten about until ~ 7 years later at a family meeting where she confronts me and wants to update me on her
having an “out of body experience” ???
It seems like out in that rural setting in a small 1 bedroom home that if you have a moonless night outside , you can’t even see your hand
in front of your face and there are no external light sourcing as coming from streetlights when in town. Also with no animal presence, the
ambient noise level floor is about 20 db below a mouse urinating on a cotton ball. The next staging is having the aunt retired to bed on
a Saturday nite and well into a sound sleep proceeding into a early Sunday morning . Add a gradual transition into the onset of a very silent
light rain., on.up to the drastic point of a violent clap of thunder tailing its initial lightning bolt. Now add the awakening of the aged aunt by
the initial noise ….BUT…now additionally having the music, creating the presence of a heavenly chorus being heard within the pitch dark
room. After the initial shock and reconnoitering the sounds origination source, as well as getting up to turn on the light switch, the music source
was coming from the table model radio. It having the music of an early morn church service from the radio.
Needless to say, the explanation was the lightning strike coming in on the power line , being in excess of the PIV of the diode , it shorted
its junction, thus activating the radio. Needless to say , when repairing her then “always on” the 1N4000 series of diode family had come
on the design scene so I assigned a more generous PIV rating of the ‘4007 series to the replacement task.
End of story
73’s de Edd
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:So..........what is the difference between a 50B5 and a 50C5? They both function exactly the same. Their only real difference is pin layout. Why were they both developed?
:
:Thomas
Thomas