neazoi
Advanced Member level 6
It's all about "hard to find components"
EL504 uses 6.3V so such a transformer can be easily found.
But EL504 is harder to find than the PL504. I have taken out of old TV sets many PL504.
On the other side PL504 uses 27V but such a transformer is hard to get.
The good thing is that at 27V the current is only 300mA, so this can be easily supplied by small diodes and 5x20W parallel brick resistors easily available. Not to mention the higher cost of the transformer.
For HV "isolation" a back to back neon transformer (easily available) could be used but these are at 12V or 24v seconday, not 27v. So the filaments cannot be operated using this one.
The philosophy is that a tube transmitter is ALWAYS dangerous, either you isolate it with a transformer or not. There will allways be that little top cap of the tube (not to mention the air variables etc) and other parts that have a high potential. Personaly I would not put ANY tube transmitter on my desk among woth other things, papers etc. but in a separate place.
So If someone isolates the chassis and the knobs, there will be no danger of using such a transmitter.
I have made the front cover using synthetic plastic glass and the knobs have no metalic parts. The only metalic parts are the antenna plugs (which are connected to the EARTH and not to the negative side of the supply, and the power switch (which is mounted on the synthetic glass only).
There is a little glitch though, the audio RCA jack, I will have to figure this out.
EL504 uses 6.3V so such a transformer can be easily found.
But EL504 is harder to find than the PL504. I have taken out of old TV sets many PL504.
On the other side PL504 uses 27V but such a transformer is hard to get.
The good thing is that at 27V the current is only 300mA, so this can be easily supplied by small diodes and 5x20W parallel brick resistors easily available. Not to mention the higher cost of the transformer.
For HV "isolation" a back to back neon transformer (easily available) could be used but these are at 12V or 24v seconday, not 27v. So the filaments cannot be operated using this one.
The philosophy is that a tube transmitter is ALWAYS dangerous, either you isolate it with a transformer or not. There will allways be that little top cap of the tube (not to mention the air variables etc) and other parts that have a high potential. Personaly I would not put ANY tube transmitter on my desk among woth other things, papers etc. but in a separate place.
So If someone isolates the chassis and the knobs, there will be no danger of using such a transmitter.
I have made the front cover using synthetic plastic glass and the knobs have no metalic parts. The only metalic parts are the antenna plugs (which are connected to the EARTH and not to the negative side of the supply, and the power switch (which is mounted on the synthetic glass only).
There is a little glitch though, the audio RCA jack, I will have to figure this out.
