[jonathan c]

It's 2:20am on the east coast of the US. I want to go to bed. I REALLY want to go to sleep. I can't. I just....CAN'T! My recent order of 10 Cossor (GEC) 6J5G / L63 (mislabled as 6C5G) arrived this week and I just finished testing and matching them. Got a set of four in Telemachus. I CAN'T STOP LISTENING to this amplifier. My VC is singing so sweetly right now. Everything I loved about the amp when using Tung Sol VT-94 as drivers has been met and surpassed with L63. I really liked the L63 in my GOTL. I absolutely love it in Telemachus paired with the EML 300B. The tone is so rich and wet, the impact is visceral, and the detail is so palpable. This amp is such a gem. It's so unnecessary for my needs yet I can't see ever downsizing from this. Anyone looking to purchase this amp do yourself a favor and make absolutely sure you have a DAC that is up to the task of feeding this beast. It's not lost on me the supporting roles that my upgraded Onyx and SU-6 are playing in my sonic bliss. Oh man, as I type a Stevie Ray Vaughan track has started in my playlist. I was hoping to go to sleep, my body needs it, but alas I don't have the willpower to press STOP. I need help...

You are on the East Coast…close enough…send Telemachus my way…

 

[jonathan c]

I wield the baton. Sometimes the whip.

Mansoner or Mansonee ?

 

[DecentLevi]

Haven't heard about the magnet test before - can you please elaborate?
I have an N52 magnet that supposedly can pick up 50lbs with a flat surface.

I personally would be wary of trying magnets around radio tubes, for a risk of delicately balanced internals becoming dislodged. Has that been the experience of anyone who has tried that?

 

[mordy]

I personally would be wary of trying magnets around radio tubes, for a risk of delicately balanced internals becoming dislodged. Has that been the experience of anyone who has tried that?

Well, what I am describing now is not for the fainthearted and probably shouldn't be done, but I had to do something to save a Tung Sol BGRP tube (12SN7).
The tube is labeled Arcturus with a date code of 3/4 - perhaps April 1943. The little heat radiator clip above the top mica had come loose, and I did not want it to cause a short.
By taping on a little 4mm magnet on the top of the tube glass I was able to position the clip away from any internal structure.

It is a very small and not very strong magnet:

This inelegant contraption actually works - the tube glow is nice:

For some reason the addition of the magnet and the tape seems to magnify the tube glow for a spectacular night effect:

BTW, the other use I found for these little magnets (apart from refrigerator use) is to use them to connect test leads and wires.
Now, about the solution to a loose metal piece inside a tube the magnet may work, but I would be leery of using it long term - not worth it if something would happen to your equipment.
Homework: What are the differences between magnets rated N35, N42 and N52?
PS: Decided to test a very strong magnet that I have on a couple of tubes. This magnet is so strong that I have to wrestle it off a flat ferrous surface. I was worried that it might pull off the anode caps but on the two tubes I tried nothing happened - apparently the anode caps are not ferrous at all. Same thing with the tube pins - no magnetic attraction. However, the internal shrouds in the tubes were ferrous, but because of the distance from the glass to the inside shroud on ST type tubes there wasn't much of a pull.
This tube is suspended in the air, held by the magnet - looks scary, eh?

Don't worry, I only used tubes from my BTB (Busted Tube Box) - have about 20 such tubes...
In conclusion, I have no idea of the effect of a strong magnetic field on a tube, but I don't think that the tube will be damaged by a strong magnet.

 

[LoryWiv]

Well, what I am describing now is not for the fainthearted and probably shouldn't be done, but I had to do something to save a Tung Sol BGRP tube (12SN7).
The tube is labeled Arcturus with a date code of 3/4 - perhaps April 1943. The little heat radiator clip above the top mica had come loose, and I did not want it to cause a short.
By taping on a little 4mm magnet on the top of the tube glass I was able to position the clip away from any internal structure.

It is a very small and not very strong magnet:

This inelegant contraption actually works - the tube glow is nice:

For some reason the addition of the magnet and the tape seems to magnify the tube glow for a spectacular night effect:

BTW, the other use I found for these little magnets (apart from refrigerator use) is to use them to connect test leads and wires.
Now, about the solution to a loose metal piece inside a tube the magnet may work, but I would be leery of using it long term - not worth it if something would happen to your equipment.
Homework: What are the differences between magnets rated N35, N42 and N52?
PS: Decided to test a very strong magnet that I have on a couple of tubes. This magnet is so strong that I have to wrestle it off a flat ferrous surface. I was worried that it might pull off the anode caps but on the two tubes I tried nothing happened - apparently the anode caps are not ferrous at all. Same thing with the tube pins - no magnetic attraction. However, the internal shrouds in the tubes were ferrous, but because of the distance from the glass to the inside shroud on ST type tubes there wasn't much of a pull.
This tube is suspended in the air, held by the magnet - looks scary, eh?

Don't worry, I only used tubes from my BTB (Busted Tube Box) - have about 20 such tubes...
In conclusion, I have no idea of the effect of a strong magnetic field on a tube, but I don't think that the tube will be damaged by a strong magnet.

You are a brave soul, @mordy. Tube suspending mid-air as one attempts to re-position it's internal organs? And now for my next trick...

 

[BzzzzzT]

I personally would be wary of trying magnets around radio tubes, for a risk of delicately balanced internals becoming dislodged. Has that been the experience of anyone who has tried that?

I got this trick from Robert B. Tomer. He was considered the foremost expert on tube operation and service during the golden era of tubes. Mr. Tomer was charged with the task of determining why tubes fail for the US military and developing best practices regarding design and troubleshooting. He was the director and head of a large lab tasked with going through the millions of service records taken from every branch of the service. He was also consulted by major tube makers of the day regarding failures and changes to facilitate stability. He dealt with all the computers used by the military during the day. Each of these used 1000s of tubes and stability and troubleshooting was paramount. This trick comes from one of the books he wrote regarding tube failures and troubleshooting.

 

[BzzzzzT]

Well, what I am describing now is not for the fainthearted and probably shouldn't be done, but I had to do something to save a Tung Sol BGRP tube (12SN7).
The tube is labeled Arcturus with a date code of 3/4 - perhaps April 1943. The little heat radiator clip above the top mica had come loose, and I did not want it to cause a short.
By taping on a little 4mm magnet on the top of the tube glass I was able to position the clip away from any internal structure.

It is a very small and not very strong magnet:

This inelegant contraption actually works - the tube glow is nice:

For some reason the addition of the magnet and the tape seems to magnify the tube glow for a spectacular night effect:

BTW, the other use I found for these little magnets (apart from refrigerator use) is to use them to connect test leads and wires.
Now, about the solution to a loose metal piece inside a tube the magnet may work, but I would be leery of using it long term - not worth it if something would happen to your equipment.
Homework: What are the differences between magnets rated N35, N42 and N52?
PS: Decided to test a very strong magnet that I have on a couple of tubes. This magnet is so strong that I have to wrestle it off a flat ferrous surface. I was worried that it might pull off the anode caps but on the two tubes I tried nothing happened - apparently the anode caps are not ferrous at all. Same thing with the tube pins - no magnetic attraction. However, the internal shrouds in the tubes were ferrous, but because of the distance from the glass to the inside shroud on ST type tubes there wasn't much of a pull.
This tube is suspended in the air, held by the magnet - looks scary, eh?

Don't worry, I only used tubes from my BTB (Busted Tube Box) - have about 20 such tubes...
In conclusion, I have no idea of the effect of a strong magnetic field on a tube, but I don't think that the tube will be damaged by a strong magnet.

I do not suggest taping things to the glass as it could effect the stability of the glass over time. Magnets are used simply as the test for interference as I stated. I don't really know what you guys are hoping to achieve??? You just need to put it in the general vicinity to check for changes in amplitude of the superimposed interference.

 

[triod750]

I don't really know what you guys are hoping to achieve???

It was easy, by reading what Mordy wrote, to understand what he was trying to achieve; preventing a short from a loose clip .

 

[BzzzzzT]

It was easy, by reading what Mordy wrote, to understand what he was trying to achieve; preventing a short from a loose clip .

I missed the first part and read the 2nd part of the post, and this led to the confusion. I thought this was about using a magnet to check for interference and an attempt to use one to prevent it.

 

[BzzzzzT]

I got this trick from Robert B. Tomer. He was considered the foremost expert on tube operation and service during the golden era of tubes. Mr. Tomer was charged with the task of determining why tubes fail for the US military and developing best practices regarding design and troubleshooting. He was the director and head of a large lab tasked with going through the millions of service records taken from every branch of the service. He was also consulted by major tube makers of the day regarding failures and changes to facilitate stability. He dealt with all the computers used by the military during the day. Each of these used 1000s of tubes and stability and troubleshooting was paramount. This trick comes from one of the books he wrote regarding tube failures and troubleshooting.

Sorry I mist

I personally would be wary of trying magnets around radio tubes, for a risk of delicately balanced internals becoming dislodged. Has that been the experience of anyone who has tried that?

Sorry I misread the post and thought you guys were talking about using magnets to test for interference. I should not stay up so late reading posts when I should be in bed.

 

[BzzzzzT]

Well, what I am describing now is not for the fainthearted and probably shouldn't be done, but I had to do something to save a Tung Sol BGRP tube (12SN7).
The tube is labeled Arcturus with a date code of 3/4 - perhaps April 1943. The little heat radiator clip above the top mica had come loose, and I did not want it to cause a short.
By taping on a little 4mm magnet on the top of the tube glass I was able to position the clip away from any internal structure.

It is a very small and not very strong magnet:

This inelegant contraption actually works - the tube glow is nice:

For some reason the addition of the magnet and the tape seems to magnify the tube glow for a spectacular night effect:

BTW, the other use I found for these little magnets (apart from refrigerator use) is to use them to connect test leads and wires.
Now, about the solution to a loose metal piece inside a tube the magnet may work, but I would be leery of using it long term - not worth it if something would happen to your equipment.
Homework: What are the differences between magnets rated N35, N42 and N52?
PS: Decided to test a very strong magnet that I have on a couple of tubes. This magnet is so strong that I have to wrestle it off a flat ferrous surface. I was worried that it might pull off the anode caps but on the two tubes I tried nothing happened - apparently the anode caps are not ferrous at all. Same thing with the tube pins - no magnetic attraction. However, the internal shrouds in the tubes were ferrous, but because of the distance from the glass to the inside shroud on ST type tubes there wasn't much of a pull.
This tube is suspended in the air, held by the magnet - looks scary, eh?

Don't worry, I only used tubes from my BTB (Busted Tube Box) - have about 20 such tubes...
In conclusion, I have no idea of the effect of a strong magnetic field on a tube, but I don't think that the tube will be damaged by a strong magnet.

Sorry for the confusing response. My monitor clipped the first part of your post and I saw only the 2nd part. I though you were talking about using the interference test. Late night confusion.

 

[mordy]

Sorry for the confusing response. My monitor clipped the first part of your post and I saw only the 2nd part. I though you were talking about using the interference test. Late night confusion.

Would you mind describing how you do an interference test and how to interpret it?

 

[mordy]

I do not suggest taping things to the glass as it could effect the stability of the glass over time. Magnets are used simply as the test for interference as I stated. I don't really know what you guys are hoping to achieve??? You just need to put it in the general vicinity to check for changes in amplitude of the superimposed interference.

I have seen writings (JACMusic) that tube coolers attached to the tube glass could affect the stability of the glass envelope because of different temperatures on the glass, leading to hairline cracks and eventual loss of vacuum. Don't have much experience with tube coolers so can't have an opinion. However, lots of old tubes have big paper stickers attached to them and they don't seem to do any harm. In the same vein I don't think that a little piece of scotch tape will damage the glass envelope.

 

[Capunk]

Hi again all,
Previously I have a Hum noise issue that was very audible from my speaker when the pre-amp is on.
I have tested various scenarios and tried many electric outlets in my house with no solutions avail.
If @SonicTrance or anyone here has a solution to this, please do let me know.
Cheers

 

[Erwinatm]

Hi again all,
Previously I have a Hum noise issue that was very audible from my speaker when the pre-amp is on.
I have tested various scenarios and tried many electric outlets in my house with no solutions avail.
If @SonicTrance or anyone here has a solution to this, please do let me know.
Cheers

1. Is the hum also audible from headphone out?
2. Try to pull all conecting cables out -) RCA/XLR. Is it still humming?