• 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.

GU 19 VS GU 19-1 What's the difference ?

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so maybe some of you know is there any difference ?
I simply have a source that can give me GU 19 tubes they dont have the -1 written after the GU 19 are they different from the GU 19-1?
at some pics I see some added caps dishes inside the GU 19 that are not present at GU 19-1 atleast not in the ones I have.
ok heres the thing , I just inserted the GU 19 not the GU 19-1 but 19 version and from what I read in the spec sheet that came with the old packaging the cathode current is much bigger , as I now inserted them in the Priboi , I started adjusting the idle current which for them seems to be much higher since with previous settings the 6R3S-1 tube was running at normal , now as I played some music in the background just to make sure signal is going through in one channel the cathode fuse simply blew itself like an explosive , before that I had a 1A rated fuse which simply gave up without any noise before I had the chance to see that then I placed a 3.15A fuse which at first was okay but once the bass cam on in the song it suddenly burst itself into a million tiny pieces of glass with a loud bang.

Can anyone tell me why that happened? is it simply because of overcurrent or is there a problem ?
ok in case anyone's interested which doesn't seem the case , I continued to regulate the bias current and the next time i switched the power on the fuse wasn't blowing anymore. and everything was ok, now all tubes work , I wonder what caused the fuse to blow in the first place ?

can there be something that can happen to a tube if it has been stored out of use for decades? visually the tubes were all ok but as I said in one channel at first the fuse blew two times and now it works and I haven't done anything other than set up a higher bias current since it was low at first.
Those are the type of tubes that are oscillating when they are still in the box. You need to put 4 to 5k grid stop resistor near the control grid and wire wound 4 ohmers on the plate and screen grid. Also about a 10 ohm 3 to 5W metal oxide resistor cathode to ground is better than the fuse. Grounding one side of the heater is not a bad idea either. I like to use sweep tubes in my amps and these measures keep them tame.
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