[BugleBoy]

Quote:

I don't think that resistor by itself caused the hum.
It could have been done earlier with a bad tube and damaged the resistor changing it's resistance.
I don't know how hot this resistor gets maybe it should be a higher wattage so it don't cook itself to death.
What would be good is if some other people took pictures of this resistor and  I could see if they are cooking.

 
Yeah that will be great if others can post some close-up pics of this resistor on their CS-300.

 

[BugleBoy]

Quote:

It is a special resistor. Could you imagine what the cost would have been had you shipped it back to your distributor for > repairs > wait > wait > wait > $$$ > shipping charges back to you. You saved a bundle for just spending 40 cents and the soldering/electronics know-how. Excellent teamwork on yours and Glenn's part. Teamwork!

 
Indeed...when you put it that way. Also, Glenn's solution was very timely. On Friday I had already had a chat with Rage Audio here in Sydney...and was planning on taking the amp to them for repairs on Saturday. But Glenn's post on Friday evening made me pause...and consider trying to fix it myself.
 
i am just glad it worked out the way it did!...Fixed the Amp, got rid of the HUM and saved all the $$$ in repair costs. Couldn't have asked for more...

 

[2359glenn]

I circled the capacitors that can be causing the hum

 

[ardilla]

Why do you think those capacitors are responsible for humming - and what how would changing them help?
 
And what kind of capacitors might be better?
Quote:

I circled the capacitors that can be causing the hum

 

[2359glenn]

Those are the capacitors that filter the pulsating DC from the rectifiers to pure DC.
I do not recommend a specific brand but those are cheap generic capacitors just change them with
the same value and voltage and make sure polarity is right or they go boom.
The one on the far left can be increased to 220uf @ 350 volts that would give more filtering.
For the screen grids and driver
If you increase the values of the other caps the filtering would be better but the DC voltage
would increase. Not sure the tubes would like that.

 

[BugleBoy]

Quote:

Those are the capacitors that filter the pulsating DC from the rectifiers to pure DC.
I do not recommend a specific brand but those are cheap generic capacitors just change them with
the same value and voltage and make sure polarity is right or they go boom.
The one on the far left can be increased to 220uf @ 350 volts that would give more filtering.
For the screen grids and driver
If you increase the values of the other caps the filtering would be better but the DC voltage
would increase. Not sure the tubes would like that.

 
Aren't the ELNA's (as seen in the Pic) better capacitors compared to most others? Without really recommending a brand...are you able to advise what we should be looking for when replacing these capacitors (maybe different type, construction etc)?

 

[2359glenn]

Quote:

 
Aren't the ELNA's (as seen in the Pic) better capacitors compared to most others? Without really recommending a brand...are you able to advise what we should be looking for when replacing these capacitors (maybe different type, construction etc)?

Those are really run of the mill capacitors nothing wrong with them really
The problem better capacitors usually require more room they are bigger.
The best capacitors are probably motor run capacitors they are oil filled
But would have to be mounted on top of the chassis they would never fit
were those Elna caps are

 

[BugleBoy]

Quote:

Those are really run of the mill capacitors nothing wrong with them really
The problem better capacitors usually require more room they are bigger.
The best capacitors are probably motor run capacitors they are oil filled
But would have to be mounted on top of the chassis they would never fit
were those Elna caps are

OK got it...Thanks

 

[ardilla]

Capacitor swapping on the Leben CS300XS mod
 
Quote: http://www.head-fi.org/t/415214/the-leben-cs300xs-thread/1245#post_8662788

I have modified my Leben CS300. It happened after the amp was damaged in a tube-rolling accident and an resistor blew up. This can seem dramatic but in this case the damage was benign and easy to repair. I brought the amp to a very experienced tube technician and also accepted his recommendation to change the coupling capacitors, with a restore guarantee without cost.
 
At the same time, I showed him some upgrades from the Polish magazine and the upgrade capacitors in the CS300XS (compared to CS300). There are a few capacitors that are different and he said that the capacitors in the XS are better but that the importance for sound quality was marginal or maybe not audible. This is very much in accordance with Skylab's impressions from listening. He said that the component in the amp are not expensive but of good quality and build quality is very good.
 
I think that the improvement of the upgraded coupling capacitors is substantial. The upgrade capacitors are Duelund capacitors made in Denmark. Duelund capacitors have a good reputation as high-end components. They are unfortunately expensive and four are needed. You can see them on the picture. I have placed one of the original capacitors above the third Duelund resistor from the left in the picture for comparison. They are much bigger but are not of different capacitance value.
 
It is difficult to evaluate the change in sound in such modifications. The upgrade took some time and the new capacitors have to burn-in. I have not had any possibility of an A-B comparison to an unmodified Leben but I am convinced that sound became smoother with better dynamics and improved bass impact. The difference is substantial.
 
 
 

http://cdn.head-fi.org/2/24/900x900px-LL-24015450_2011_06110005.jpeg
 
 

 
 
 
Quote: http://www.head-fi.org/t/415214/the-leben-cs300xs-thread/1245#post_8661263

Here's a Leben CS300X that was modified with V-Caps, etc.
 
Leben CS300X [Custom Version]
 

http://www.highfidelity.pl/foto_testy/1008/leben/02.jpg
 

 

[ardilla]

Tube rolling damage to Leben CS300XS cpacitors
 
 
Quote: http://www.head-fi.org/t/415214/the-leben-cs300xs-thread/1260#post_8669260

Quote:

Hello Anders, 
Please, what kind of problem caused the accident during the tube rolling?
Thanks!

I used a tube that is electrically equivalent with EL84 but not pin compatible, a way to get NOS tubes very cheap. I bought the tubes with adapters from a reputable tube company but it seems that the pinout is different from the standard on CS300. They have changed the description after that, but when I bought the tubes it looked like a drop in replacement with the adapters. When I turned on the amp, it began to smoke. I turned it off directly and the damage was limited, a resistor burned and an inexpensive capacitor was slightly damaged and replaced. As a compensation I got a quad of NOS Mullard EL84 from the tube company, so when all was cleared up it was a rather nice experience.
 
With all the talk about humming Lebens, I sometimes wonder how many that could have been damaged by tube rolling? Obviously, an incompatible tube need not burn a component in the amp, it could instead result in a more subtle damage. Nowadays, I only use 12AX7, 5751, EL84 or close substitutes.

 

[2359glenn]

I was just saying to replace the existing capacitors with new ones.
Not doing a mod to different capacitors.
The coupling capacitors are different capacitors then the ones I said to change
are filter capacitors in the power supply.

 

[Clayton SF]

I still own my Leben CS600 but it is in storage right now because I am now listening to the 300B mono blocks that Glenn built. But I have never rolled tubes in my Leben. It still has its stock tubes. I'm afraid to roll tubes in a $6K amp.

 

[MorbidToaster]

I still own my Leben CS600 but it is in storage right now because I am now listening to the 300B mono blocks that Glenn built. But I have never rolled tubes in my Leben. It still has its stock tubes. I'm afraid to roll tubes in a $6K amp.

If it ain't broke don't fix it.

 

[BugleBoy]

Quote:

I still own my Leben CS600 but it is in storage right now because I am now listening to the 300B mono blocks that Glenn built. But I have never rolled tubes in my Leben. It still has its stock tubes. I'm afraid to roll tubes in a $6K amp.

 
Tube rolling can be a rewarding experience....on some amps.
 
Don't know about CS600; but the CS300 can really shine with some good NOS tubes...it seems like a no brainer IMHO.

 

[BugleBoy]

Hey Glenn...how can I find out about your amps. Do you have as website?
 
Pardon my ignorance if it is common knowledge on Head-fi.