10-27-2023, 12:29 PM
Some else that was ruminating in my pea sized brain was if you keep the current draw close to the original spec you could go single ended w/one 1C5. It would still make more output by a nose. If you look @ the diagram the opt pri resistance is almost 2K. This means that there is almost a 15v drop in the plate voltage at the 1A5's.
Using the 1C5 the dc resistance of the replacement transformer is going to be something around 400 ohms (16k vs 50K) I would think. So the plate voltage @ the 1C5's is going to be higher than the 1A5's
With this lower resistance primary tubes (1C5's) are going to pull more current at 90v and make sound. But what if we removed one of them? If we use a opt for 8K to vc and coverup the bottom socket as shown on the diagram. Just use the top socket with a 1C5 it will make as much sound as it did w/the pair of 1A5's and it will keep the plate current down to 10ma or so. With the pair of 1C5's it will run your B batteries down quicker.
A quick note there is a big difference between dc resistance which you can measure w/an ohm meter across the winding of a transformer and the ac impedance. That is the ac load that the winding presents to a circuit. In this case the plate of the tube. The 1900 ohms that is shown on the diagram has nothing to do w/the ac load it presents to the plate of the 1A5, there is no correlation other than the higher the resistance the higher the impedance but this is a rough guess which is mostly true. The dc resistance is there to give you an idea what it should read and if it's open or not. That's it.
Somewhere around here I have a 48-145 which is the loctal version with se output stage. It a good player and impressive for the amount of battery juice it uses. Without being connected to the a p/s or a wall socket you don't get a lot of the noise that you hear on other set that plugin.
OBTW to answer your question I'm not sure. Because I don't know what the impedance of the vc is. That's the long answer. the short one is it's better than a an open one.
https://philcoradio.com/library/download...6-1947.pdf
https://philcoradio.com/library/download...6-1947.pdf
Using the 1C5 the dc resistance of the replacement transformer is going to be something around 400 ohms (16k vs 50K) I would think. So the plate voltage @ the 1C5's is going to be higher than the 1A5's
With this lower resistance primary tubes (1C5's) are going to pull more current at 90v and make sound. But what if we removed one of them? If we use a opt for 8K to vc and coverup the bottom socket as shown on the diagram. Just use the top socket with a 1C5 it will make as much sound as it did w/the pair of 1A5's and it will keep the plate current down to 10ma or so. With the pair of 1C5's it will run your B batteries down quicker.
A quick note there is a big difference between dc resistance which you can measure w/an ohm meter across the winding of a transformer and the ac impedance. That is the ac load that the winding presents to a circuit. In this case the plate of the tube. The 1900 ohms that is shown on the diagram has nothing to do w/the ac load it presents to the plate of the 1A5, there is no correlation other than the higher the resistance the higher the impedance but this is a rough guess which is mostly true. The dc resistance is there to give you an idea what it should read and if it's open or not. That's it.
Somewhere around here I have a 48-145 which is the loctal version with se output stage. It a good player and impressive for the amount of battery juice it uses. Without being connected to the a p/s or a wall socket you don't get a lot of the noise that you hear on other set that plugin.
OBTW to answer your question I'm not sure. Because I don't know what the impedance of the vc is. That's the long answer. the short one is it's better than a an open one.
https://philcoradio.com/library/download...6-1947.pdf
https://philcoradio.com/library/download...6-1947.pdf
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
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