simple se blowing rectifier and fuse

newtube · 12th May 2009, 08:27 PM

Guys, i just finished assembling my simple se and on powering up it is fine for about 5 seconds then the rec tube crackles and it blows the fuse, this happens with all tubes fitted or just the rectifier. . . .
Any pointers as to what can cause this?
I'm so fed up as iv'e been looking forward to this all day

p.s, this happens even if i swap the rec tube for another

rknize · 12th May 2009, 08:43 PM

Can you tell us more about your setup? What power transformers? What B+ voltage do you see? Any pictures of the PCB? Have you tried with the output transformers disconnected? Sounds like a short somewhere or an incorrect resistor value or something along those lines. Check your work, especially the resistors and the polarity of the capacitors in the power supply section.

DimZ · 13th May 2009, 07:30 AM

... wrong post

newtube · 13th May 2009, 12:12 PM

The transformer is a hammond 373 bx, im using 6l6gc tubes and a gz34 rectifier tube, no freds, and the output trannies are not yet connected.

I can't measure the b+ at the mo as my meter batteries are flat!

Everything looks fine, the amp powers up fine without the rec tube in, if the rec tube is installed the tubes glow for 5 seconds then the rec tube crackles and blows the fuse

vuohi · 13th May 2009, 12:36 PM

Are you using JJ GZ34s? I had a faulty one, and searching the web I discovered that there have been relatively many of them failing. Apparently a bad batch or something.

newtube · 13th May 2009, 12:42 PM

It is indeed a jj gz34, i tried 2 of them.

vuohi · 13th May 2009, 01:42 PM

My faulty JJ had some metal flakes inside the bulb after the failure. You could check the valves for obvious visual faults like those flakes or misaligned parts. And of course, check your solder joints and double check parts values and possible shorts.

Mickeystan · 13th May 2009, 01:56 PM

Double check the installation of the high tension rectifier filter capacitors to assure they are installed correctly. If either of these accidentally got installed backwards, this will blow the fuse once the rectifier tube goes into conduction and begins to try and charge them. Thus, be sure the capacitors (+) terminal is oriented to the correct pad on both capacitors.

Doug

newtube · 13th May 2009, 05:08 PM

does c3 cap have a polarity?
i notice the lettering on mine is facing the opposite way to the tubelab pics

n_maher · 13th May 2009, 08:20 PM

Quote:

Originally posted by newtube
does c3 cap have a polarity?
i notice the lettering on mine is facing the opposite way to the tubelab pics

No, C3 is a small film cap and does not have a polarity.

12th May 2009, 08:27 PM	#1
newtube diyAudio Member Join Date: Mar 2009	simple se blowing rectifier and fuse Guys, i just finished assembling my simple se and on powering up it is fine for about 5 seconds then the rec tube crackles and it blows the fuse, this happens with all tubes fitted or just the rectifier. . . . Any pointers as to what can cause this? I'm so fed up as iv'e been looking forward to this all day p.s, this happens even if i swap the rec tube for another

12th May 2009, 08:43 PM	#2
rknize diyAudio Member Join Date: Feb 2009 Location: Chicagoland	Can you tell us more about your setup? What power transformers? What B+ voltage do you see? Any pictures of the PCB? Have you tried with the output transformers disconnected? Sounds like a short somewhere or an incorrect resistor value or something along those lines. Check your work, especially the resistors and the polarity of the capacitors in the power supply section. __________________ Russ http://www.knizefamily.net/russ/cate...ics/tubeaudio/

13th May 2009, 01:56 PM	#8
Mickeystan diyAudio Member Join Date: Jan 2008	One other possibility causing fuse blowing... Double check the installation of the high tension rectifier filter capacitors to assure they are installed correctly. If either of these accidentally got installed backwards, this will blow the fuse once the rectifier tube goes into conduction and begins to try and charge them. Thus, be sure the capacitors (+) terminal is oriented to the correct pad on both capacitors. Doug

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13th May 2009, 07:30 AM	#3
DimZ diyAudio Member Join Date: Nov 2007	... wrong post

13th May 2009, 12:12 PM	#4
newtube diyAudio Member Join Date: Mar 2009	The transformer is a hammond 373 bx, im using 6l6gc tubes and a gz34 rectifier tube, no freds, and the output trannies are not yet connected. I can't measure the b+ at the mo as my meter batteries are flat! Everything looks fine, the amp powers up fine without the rec tube in, if the rec tube is installed the tubes glow for 5 seconds then the rec tube crackles and blows the fuse

13th May 2009, 12:36 PM	#5
vuohi diyAudio Member Join Date: Mar 2009	Are you using JJ GZ34s? I had a faulty one, and searching the web I discovered that there have been relatively many of them failing. Apparently a bad batch or something.

13th May 2009, 12:42 PM	#6
newtube diyAudio Member Join Date: Mar 2009	It is indeed a jj gz34, i tried 2 of them.

13th May 2009, 01:42 PM	#7
vuohi diyAudio Member Join Date: Mar 2009	My faulty JJ had some metal flakes inside the bulb after the failure. You could check the valves for obvious visual faults like those flakes or misaligned parts. And of course, check your solder joints and double check parts values and possible shorts.

13th May 2009, 05:08 PM	#9
newtube diyAudio Member Join Date: Mar 2009	does c3 cap have a polarity? i notice the lettering on mine is facing the opposite way to the tubelab pics

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