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Rubicon Cap on my P3

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Tonight I turned on my Audio Note P3 power amp and smoke was coming out the top of one of the Rubicon caps next to the main 300b tube. The value of the cap is 100x220. I could easily replace the cap, but want to make sure there was not something that caused this to happen. Does anyone know of a trustworthy tube amp repair shop for tube amps here in Grand Rapids.

Follow Ups:

Update - richard hickey 15:28:27 11/10/10 (0)
Everyone,

I took the Amp to the tech today and he found that a loose solder joint on the resistor in the signal path caused huge amounts of voltage into the cap. I saw his meter hit 130 before he powered the amp down. After re-soldering the entire contact points, he hooked up his tester again and the voltage stabilized at 65.

I am now going to replace all four caps with Blackgates from Michael Percy.

I showed him all of your thoughts and asked him to test for each of the items. I also took the schematic that he used as well.

Thanks again.
Excellent Advice! Thanks To All - richard hickey 09:24:09 11/08/10 (0)
Guys,

Many thanks for the input. I have found a local gentleman here in Grand Rapids who repairs tube amps and am going to take the P3 to him this week. I just printed a schematic and your advice to give him a fast start on the diagnostics. I will definitely replace all of the caps at the same time. One more question if I may. If there are other parts that have failed is there a source I can go to? ( You probably can't answer that until I learn what else has failed)

I will revert back as soon as I know more. Be sure to stop back in a week or so as I am traveling to Scotland on business travel next week and may not hear more until after the trip.

Best Regards,
RE: Rubicon Cap on my P3 - mbhcid 05:05:23 11/08/10 (0)
I had the same problem twice with my Kit-1 a few years back (very similar schematic) and found:

the first time: The filament regulator was shorted/failed (note the filament sits 75 volts above ground) be sure to check that the regulator is a. working; and b. not shorted to the heat sink. I replaced the regulator and all was well.

the second time: I had a failed AN copper coupling cap (.39Uf in your amp according to the schematic) which was passing DC through to the output stage. I replaced the cap and all was well.

Check both and let us know how you make out.
RE: Rubicon Cap on my P3 - tubeheadz 22:14:21 11/06/10 (2)
Hi,

When you say the Rubycon cap next to the 300B, I take it you mean the cathode cap attached to pin 1 on the 300B. This is a 220uf 100v cap right?

First, I would check the 300B tubes. If you don't have access to a tube tester... swap the tubes (capacitors are cheaper than tubes)... if the other cap blows... you have a faulty tube... now replace the tubes and caps! E-mail me for my thoughts on 300B tubes.

The caps that I have had success with in this position are the Elna Silmic II at $4.50 each. Black Gates are marginally better and a lot more expensive.... take your pick...

I'm not saying that you shouldn't send your amp to an AN repair facility... but if it's just the cap... or a tube... you can repair it yourself for less than the cost of shipping.
- RE: Rubicon Cap on my P3 - richard hickey 11:37:30 11/07/10 (1)
  Thanks guys.
  
  Yes. That is the cap I am referring to. I am looking for a local tech here is Grand Rapids, Michigan to determine if there was something that caused this. I agree and am trying to save the shipping to and from California or New York as well as the potential damage in shipping. I am using the Sophia Princess 300B tubes that have around 100 hours on them.
  
  I really appreciate your thoughts and time.
  
  Regards,
  - RE: Rubicon Cap on my P3 - tubeheadz 20:16:46 11/07/10 (0)
    Hi Richard
    
    As I've often said on this forum, I don't like to get into the ebb and flow discussions of which tubes are best, however those Sophia Princess 300B tubes are generally excellent.
    
    I'm sure that you will be able to find someone locally who has a tube tester... if not, switch the tubes around as I suggested... but do not use the channel with the blown cap until that has been resolved. If you do find a kind soul with a tube tester.... label each tube with the position they came from, and test them all.
    
    You could easily replace all of the Rubycons with the excellent Panasonics, part# P10780-ND at only $1.63 each from Digikey. That would be my next suggestion. It appears as if there are 4 of them so it's not like it will break the bank. If you don't have a schematic, you can find one on the internet... I just did. You could also get the Elna Silmics and try them after the problem has been resolved... in my experience they are a touch warmer and you may prefer that.
    Ensure that the cathode resistors are in spec and that they're making a good connection to ground...
    
    If after these basic diagnostics and remedial actions... your amp is not working happily, only then would I consider the risk of packing it up and sending to one of the Audio Note authorised repair centers.
    
    Good luck... and let us know the outcome.
RE: Rubicon Cap on my P3 - R Browne 21:14:02 11/05/10 (0)
I'd contact Nick Gowan at True Sound, an authorized Audio Note repair center. Info below:

True Sound
Nick Gowan
Tel 408/370-7578
Fax 408/370-7581
gowan@tsound.com

It may be an easy fix but there could be other issues involved. On the east coast there is the option of contacting:

New York Audio Repair
(718) 377-8010
benchtech@highendaudiorepair.com
www.highendaudiorepair.com

I haven't dealt with New York Audio Repair but Nick Gowan comes highly recommended regarding Audio Note repair issues. Good luck.

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