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post #16 of 298
9/23/08 at 3:25pm
Maybe it's what's causing your hum? I've seen preamp tube filaments glow brightly when powered up, but never a rectifier. But you're seeing a white flash which to me sounds like a tube ready for failure?
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post #17 of 298
9/23/08 at 3:27pm
Quote:
Originally Posted by sclamb View Post
I just switched the amp back on again and there was the white flash in the 274B tube and a spark or two fell down to the base. Sounds like I may have to call on the 30-day warranty on the tube and get a replacement from Jack. Could this be causing the hum, and more importantly, could it be damaging the internals of the amp?
If the tube shorts, I would think the main fuse would blow. I'd still not use it with the tube in that condition. Do you have any other rectifier you could try?
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post #18 of 298
9/23/08 at 3:30pm
Thread Starter 
I will leave it switched off for now. I do not have another rectifier tube. What would be a good cheap one to get just to swap and see if it stops the hum.

This is a brand new Sophia tube so it is a bit annoying if it is faulty. I just hope it is not an internal fault on the amp that is ruining the tube.
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post #19 of 298
9/23/08 at 3:35pm
I bought a cheap NOS RCA 5V4 from thetubestore.com for $19.95 US. It sounds good to me, but I'm sure it's not nearly as good as the Sophia. I think it's a good idea to have spare tubes anyway. You never know when a tube will go out on you.
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post #20 of 298
9/23/08 at 3:41pm
Found this while perusing the Woo site:

18. What to do when my amplifier developed a light hum/noise?

This could a typical issue due to tube deterioration or it could be introduced from your input sources or sourrounding. There are several simple test procedures you may use.

1. Remove all input sources from the amp and listen to any different. If the hum/noise goes away, the noise is coming from your sources.

2. Keep your amp away from frequency emitting devices such as cell phones, radios, PDAs, ect. Noise can be picked up by tubes, especially in high gain design amp.

3. Clean tube pins with cleaning alcohol. Oxidized pins can cause mal-connection.

4. Swap the drive or power tubes from left to right channel. If the hum traveles, one of the tubes may be deteriorated.

5. Replace "good" drive, power or rectifier tubes.

6. Try a different AC wallet. Noise can be easily introduced from a poorly grounded wallet. You may also try a "cheater" plug (plug that do not have a ground) to see result.
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post #21 of 298
9/23/08 at 3:47pm
Thread Starter 
Thanks GM. I think these guidelines are relating to the sound being heard through the headphones. The hum is there even with all the ICs disconnected and I cannot hear it through the headphones. The sparking in the rectifier tube seems to suggest either a bad (new) tube or a fault in the amp itself.
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post #22 of 298
9/23/08 at 3:47pm
Gold Monkey,

I always de-oxidize my tube pins with Flitz Metal Polish. Then I use alcohol to clean off the remaining polish residue.
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post #23 of 298
9/23/08 at 3:49pm
Quote:
Originally Posted by sclamb View Post
I also just noticed this. When I turn on the power, I see a white flash go up the mesh plate on the Sophia tube before it start to glow orange. Is this normal?
I get the white flash too. It's more of a spark though. I only see it if I turn on the amp in the dark though. My amp is connected to a surge protector which indicates that I have a building wiring fault though. I wonder if that has anything to do with it.
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post #24 of 298
9/23/08 at 3:54pm
Thread Starter 
Would this do as a cheap replacement to test the amp with:

5U4G / 5C3S (5Ц3С) Double Diode
The Svetlana 5C3S (5Ц3С) double diode is known in the west as 5U4G.
€ 13,10 each

or this:

JJ Electronics GZ34 (5AR4)Dual Rectifier
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post #25 of 298
9/23/08 at 3:55pm
Thread Starter 
Quote:
Originally Posted by Ragonix View Post
I get the white flash too. It's more of a spark though. I only see it if I turn on the amp in the dark though. My amp is connected to a surge protector which indicates that I have a building wiring fault though. I wonder if that has anything to do with it.
INteresting. Does your amp hum at all?
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post #26 of 298
9/23/08 at 4:05pm
Quote:
Originally Posted by sclamb View Post
Would this do as a cheap replacement to test the amp with:

5U4G / 5C3S (5Ц3С) Double Diode
The Svetlana 5C3S (5Ц3С) double diode is known in the west as 5U4G.
€ 13,10 each

or this:

JJ Electronics GZ34 (5AR4)Dual Rectifier
I have a Svetlana 5U4G (5Ц3С) as a backup. Yes it works fine but it doesn't sound as good as my 5V4....
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post #27 of 298
9/23/08 at 4:06pm
You really need to get another rectifier in order to fully rule out a problem with the Sophia. I tuned my WA6 SE on a little while ago and it is very quiet. I even put my ear to the PSU. I would think that any 5AR4 or 5U4G would be suitable. I received a 5AR4 with my amp and purchased the Sophia a few months later.
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post #28 of 298
9/23/08 at 4:13pm
Thread Starter 
Quote:
Originally Posted by atbglenn View Post
I have a Svetlana 5U4G (5Ц3С) as a backup. Yes it works fine but it doesn't sound as good as my 5V4....
I just want to get a tube quickly to rule out a problem with the amp itself, so I not too worried about the quality. I just don't want to have to ship it back to the US!

Jack should replace the Sophia if it is faulty as it has a 30 day warranty which I am still within.

If any UK Head-Fiers have a tube I can borrow to check the amp that would be great (especially if you are near London or Hatfield). A beer awaits
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post #29 of 298
9/23/08 at 4:15pm
Thread Starter 
Quote:
Originally Posted by breakfastchef View Post
You really need to get another rectifier in order to fully rule out a problem with the Sophia. I tuned my WA6 SE on a little while ago and it is very quiet. I even put my ear to the PSU. I would think that any 5AR4 or 5U4G would be suitable. I received a 5AR4 with my amp and purchased the Sophia a few months later.
I am waiting to hear from Jack. I will order a cheap tube just to check the amp out first. I really hope this is a faulty Sophia tube and not a problem that will require shipping the amp back to Jack.
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post #30 of 298
9/23/08 at 7:27pm
Thread Starter 
I just saw this article:

Emission Labs - Introduction

Note this section:

A white spark is NOT a bad tube issue, and it is NOT a short circuit of the tube. Vacuum can not short circuit.

Question: Why does it only occur with a new tube, and not with old tubes?

Answer: It is easier to exceed the maximum peak current when a tube is new, when it has highest emission reserve. So you may observe this with larger tubes, and with newer tubes. But it can happen to any tube, when the electronic circuit is not good. In that case it will particularly happen when they are a high emission kind of tube.

Another article here about the 274 tube that mentions white sparks:

http://www.jacmusic.com/fullmusic/da...-datasheet.pdf

This is sounding more and more like I have a bad amp
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