Do Vacuum Tube Amplifiers Emit X-Rays at Lower Voltages and Frequencies?

[Salvador]

http://www.pastisch.se/faktiskt/c-core00.jpg

the transformer is actually quite easy to open , simple take it off , then open the core tensioner steel and you have two C cores that each come out from their respective side.the rest is simply an open bobbin , its not the transformer itself that i fear it's the number of small gauge wire windings that I hate :D
I'm heating them now on my radiators since it's still the last month of winter outside , after that I'm going to put them in an oven for a while , this old russian wire enamel is pretty strong so ill turn the heat up quite a bit , i have nothing to loose anyway , I found a guy who has another Priboi and he will sell it to me for cheap money.
that was the only ad of such an amp in the whole country so i may consider myself lucky , and the ad came on exactly when mine broke :D Funny .

 

[Planobilly]

Hi guys,

I have been gone all day...just got back.

I will look at skype now.

Billy

BTW...just got a HAMEG 203-5 scope which seems to work..I know nothing about analog scopes, never owned one...lol Also a Tektronix 2205-40 which will turn on but focus control not working...These were given to me by a friend. The "fix me" pile is getting larger..lol

Cheers

 

[jim hardy]

its not the transformer itself that i fear it's the number of small gauge wire windings that I hate :D

dont unwind it ... what you want is to let whatever pushed the wires together relax, then fill the void with insulating varnish or something. Hopefully a long warm dry will achieve the relaxation for you. Dont heat enough to soften the old varnish, i'd stay below 140F.
If that fixes it try soaking the bobbin&windings overnight in a can of thin varnish. Dont get varnish in the core's air gap that'll change inductance.
PlanoB posted two great audio transformer links.

 

[Salvador]

Ok I see what I can do and report back

 

[Salvador]

Ok so for those who followed , after all my assumptions were wrong I did change now the output transformers and the amp is back in business.
now i left the transformers on a radiator for about a week, the one which had the high resistance from primary to secondary now has no resistance at all measuring with a multimeter, so it's likely it fixed itself.
the other one which had the 20 ohms between the windings still has the same fault with the same resistance as before , so i will proceed to the next step as to put it in an oven.
maybe if it works out I will have two working tube amps instead of one, since the other tube amp from which i took the transformers is also fine.

 

[Salvador]

also I have found out that of all genres classical sounds the best on this and probably many other tube amps.
i think it has something to do with the fact that due to the output having transformers the very low frequencies and the very high get kind of influenced and cut off a bit.

 

[jim hardy]

i think it has something to do with the fact that due to the output having transformers the very low frequencies and the very high get kind of influenced and cut off a bit.

There's volumes written on the subject sound of tubes vs solid state amplifiers and it ranges from very scientific inquiries with spectrum analyzers to utter bilgewater .

One author picked up on these facts
Tube amps resemble a current source because of pentode characteristics and large inductance of the output transformer . They reproduce the input signal as a current waveform.
Solid state amps resemble a voltage source because they employ feedback . They reproduce the input signal as a voltage.
Most lab tests of an amplifier use a resistor load .
For a resistor load, voltage and current waves have the exact same shape.

When there's inductance present , voltage and current waves have same shape ONLY for a sine wave. That's one of the oddities of Mother Nature's favorite shape, the sinusoid , it doesn't change shape when you integrate or differentiate it.
More complex waves such as square or Mozart will change shape.
Now a speaker is a motor with inductance and inertia in addition to resistance.
In a motor current determines torque and voltage determines speed(velocity) .
A motor when driven by a current wave of given shape will not have same motion as when driven by a voltage wave of same shape.

If you have a 'scope try it - set your function generator for square wave and drive a speaker through different amps, observing voltage across speaker.. Repeat with resistor load.

 

[Salvador]

Hmm i'll have to digest some of this , so for inductance if driven with a sinusoidal wave voltage and current run just like they do in a purely resistive load aka together?
I think i confused the inductive load for the capacitive load , hence all the fuss about the smps mains filters producing bad power factor if not corrected.

as for the tubes you mentioned a pentode amplifier but the one I have is using dual beam tetrodes in the output.Now I have to read some papers otherwise I am not that smart at telling he difference between them but I assume there is some.

 

[jim hardy]

so for inductance if driven with a sinusoidal wave voltage and current run just like they do in a purely resistive load aka together?

For an applied sine wave voltage, Inductance gives a phase shift between voltage and current. Shape doesn't change, just current wave shifts toward 'later' by a fraction of a cycle..you've heard the expression "current lags in an inductor" Human ear is not sensitive to phase.
For an applied square wave voltage, inductance will change the shape of the current wave from a square toward a triangle .
http://electronics.stackexchange.co...change-in-current-and-what-is-its-correct-for

If there is significant internal resistance, the current looks more like:

a speaker has resistance of about 70% of its nominal Z,
ie an 8 ohm speaker has ~5.6 ohms of resistance and some inductance.

old jim

 

[jim hardy]

as for the tubes you mentioned a pentode amplifier but the one I have is using dual beam tetrodes in the output.Now I have to read some papers otherwise I am not that smart at telling he difference between them but I assume there is some.

A pentode is just a tetrode with "Suppressor Grid" added close to the plate.
When the plate approaches red hot it'll emit some electrons that would be attracted to the positive screen grid.That's called 'secondary emission'.
The nearby suppressor grid is at same potential as cathode , so it tends to push those secondary electrons back toward the plate where you want them.
That's all explained in the RCA tube manual that(i think) you've downloaded.

Have fun with your tube amps. I love that blue glow ..
picture courtesy of http://gpoint-audio.com/about-valves/

Try a search on loudspeaker inductance, My google seems eager to please
http://users.ece.gatech.edu/mleach/papers/vcinduc.pdf
http://www.eminence.com/support/understanding-loudspeaker-data/
https://www.klippel.de/fileadmin/klippel/Files/Know_How/Literature/Papers/Voice_Coil_ Impedance_04.pdf

old jim

 

[dlgoff]

Now a speaker is a motor with inductance and inertia in addition to resistance.

I know how you like visuals, so I thought I'd share this Physics animations site. And as to the speaker,

A loudspeaker is a linear motor with a small range.

they have the embedded flash player image http://www.animations.physics.unsw.edu.au/jw/flash/speaker_vibrating.swf
loudspeaker page = http://www.animations.physics.unsw.edu.au/jw/electricmotors.html#loudspeakers

 

[Salvador]

I will try to resurrect the other Priboi amp that I have , that one is a 75watt per channel version , i now have one output transformer i have to finish the other one , hopefully.

as for the picture Jim posted of the glowing tubes, i think most of those photo's are a bit edited or taken with some special lens etc because as much as I have observed in real life the tubes never glow as strongly or as beautifully as they seem to in photos.
ans is that blue color from the electrons interacting with the camera or can it be seen directly with naked eyes ? I have never seen blue light from a tube with my eyes in real time.

 

[jim hardy]

ans is that blue color from the electrons interacting with the camera or can it be seen directly with naked eyes ? I have never seen blue light from a tube with my eyes in real time.

Darken the room. It's very real, but not all tube types have it.
6973 Beam Pentodes in my high school project hifi shone wonderfully.

 

[nsaspook]

http://www.jacmusic.com/techcorner/ARTICLES/English-neu/blueglow/blueglow.htm

 

[Salvador]

just if anyone's interested I managed to repair the output transformer , after carefully studying the way it's built I rewound the bobbins that were damaged and now it finally works.
so what started out as a spare not working amplifier to make this one work turned out a lesson learned and two working amplifiers.