Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: aro on February 22, 2011, 10:02:06 pm
-
I did something stupid (seems to come naturally :sad:)
I changed the output tubes on my 2204 clone and I was checking the bias with the 1 ohm method. Everything was fine, since I've done this many times.
I decided to check the plate voltage again on the first output tube. I put the probe on pin 3...and then it happened. My hand, and the probe, slid from pin 3 towards pin 2, and the probe bridged the two pins... I pulled my hand, but too late. There was a small and bright sizzling light between the two pins for about 3 seconds, then a little bit of smoke, then it stopped and everything was "fine" (visually).
The amp was still on, power tubes were lit normally, but there was no voltage on the screen cap anymore. Also no voltage on the power tubes and V1a/b (I didn't check V2 and V3). The main cap had good voltage.
Did I kill the OT? Did I kill the screen cap? Did I kill both, or even more than that...?
-
Have you checked the HT fuse?
-
Have you checked the HT fuse?
B.I.N.G.O. Thank you !
The HT fuse was gone. It's a 0.5A T. I didn't have one and I put in a 250V 1A slow blow. The voltages are back where they should be.
Now...can I leave in the 1A fuse, or should I get a 0.5?
-
Have you checked the HT fuse?
B.I.N.G.O. Thank you !
The HT fuse was gone. It's a 0.5A T. I didn't have one and I put in a 250V 1A slow blow. The voltages are back where they should be.
Now...can I leave in the 1A fuse, or should I get a 0.5?
always use the stated value.
-
Have you checked the HT fuse?
B.I.N.G.O. Thank you !
The HT fuse was gone. It's a 0.5A T. I didn't have one and I put in a 250V 1A slow blow. The voltages are back where they should be.
Now...can I leave in the 1A fuse, or should I get a 0.5?
always use the stated value.
Will do. Thanks.
-
That .5A fuse likely saved your OT. You may not be so lucky next time you short the plate to filament (basically ground) if you leave that 1A SLO BLO fuse in there. :grin:
-
Talking about OT...
I have another 2240 clone where, if I play it through an attenuator and turn down the attenuator volume entirely (thus no volume through the speaker), I can hear a click every time I play a note.
The click doesn't come through the speaker, it's from somewhere on the chassis. I was told that it's the OT, and that it's OK. It seems to come indeed from the OT "area". I have no reason to doubt the advice, but could someone confirm that?
BTW, the 22204 clone with the blown fuse doesn't do that.