• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

help !! 45 tube

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after 2-3 minutes of work the sound of high frequency starts whistling...... I don't know what to do? ? ? ? help who understands thanks Sergey Moskva

...the mistake can eat? ?
there is a bad lamp of D3A? ? . the lamp itself whistles? ? ?
or all lamps good? ?
...////////////////////////////////////////////////////////////////////////trans" lundahll 1660" alt S 4:4.5
 

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I can't see but I think that you haven't soldered your grid ressistors directly to the grid?
If not, than turn of your amp, empty caps, solder 7k ressistor directly to the socket pin as colose as possible. Same with the 680ohm ressistor on the 45 grid...
Test it then, if you can hear whistling again then:
Use a wooden or plastic stick. Pick every wire with it, when you hear diferent sound that is the problem. If you pick everything and it still whistles... God help you.
Sorry for my bad english...
 
These C-Core transformers have extremely low stray magnetic field. There shouldn't be any problems with the alignment.

The problem is, as others have already mentioned, the wiring.
I will show you a picture of a wired tube socket:
inside3.jpg

(Source:The Great Cardmatic Tube Testers)

After looking at it, look at your amplifier again :)

Riken-ohms, Ruby/Elna/Panasonic caps, Lundahl trafos, Alps pots, Gold bling-bling stuff - doesn't help anything, when your wiring is bad.

The D3A is a very high gm tube and will oscillate very easily.
Thus:
-Keep the wiring as short as possible
-Keep anode and grid wires seperate and not parallel
-Solder the grid resistor directly to the socket
-When you want to be on the safe side, use ferrite beads

Apart from that, nice amplifier :cool:
 
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