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Kit1 eating rectifier tubes--please help!

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Been through several rectifiers in the last year including a couple of pricey NOS. The NOS each lasted about 3 months with nearly daily turn on and use. Basically, on turn on they flash or spark internally and blow the fuse. After fuse replacement, the tube is dead but the rest of the tubes on the amp are fine.
Thinking of a soft start circuit to ease turn on, but what else could solve my issue?

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Re: Kit1 eating rectifier tubes--please help! - gsimon 05:08:46 01/19/06 (0)
Hi Doug ,
I would check the first cap(s) before choke.
Do not use NOS rectifiers untill problem is solved ...
Gilbert
Re: Kit1 eating rectifier tubes--please help! - profbrookes 00:14:16 01/19/06 (9)
Might be worth checking that the 300B sockets aren't arcing. Sometimes, through general wear and tear, the contacts only just make contact and there can be some arcing - especially at start-up.
This is easy to do - just remove the 300B's and squeeze the terminals together slightly with a pair of pliers (from inside the chassis).
This has happened to me with other amps in the past.
Anyway, it's worth a try.
- Re: Kit1 eating rectifier tubes--please help! - scarebus 09:54:54 01/19/06 (8)
  Once in a while I clean all tube sockets and tube probes with
  'DEOX IT'. Hook up a voltmeter at pin 4 or 6 of 5U4G and check
  the initial 'pwr-on', and go from there.
  - Thanks for suggestions. Any thoughts on - DougE 12:14:56 01/19/06 (7)
    soft start?
    Again, your input is greatly appreciated.
    Doug
    - Re: Thanks for suggestions. Any thoughts on - Kamigo 05:05:20 01/20/06 (6)
      Soft start wouldn't solve the underlying problem.
      Has your amp operated properly before, or has it had this problem since you built it?
      Rectifiers are pretty tough, and from the sounds of things you're getting a big surge through your 5U4. Are your power supply caps stock values, or did you change them? I believe the necessary value for the first caps is 47uf for a 5U4. How about voltages?
      Contact Brian directly - he seems to be able to debug problems in no time flat.
      - Re: Thanks for suggestions. Any thoughts on - scarebus 10:16:50 01/20/06 (5)
        
        In Reply to: Re: Thanks for suggestions. Any thoughts on posted by Kamigo on January 20, 2006 at 05:05:20:
        
        DougE,
        Per wiring diagram, check C1 and C2 of psu. Do you see
        any bulge on the top? Try replace them. How did the voltage
        check come out?
        
        Re: Thanks for suggestions. Any thoughts on - GTCharlie 17:45:07 01/20/06 (4)
        
        In Reply to: Re: Thanks for suggestions. Any thoughts on posted by scarebus on January 20, 2006 at 10:16:50:
        
        Check the first capacitor immediately after the 5U4 rectifier, before the choke. And if you replaced what came in the box, check value. Say, between 20 something uF up to say 47uF should do very fine. Too much capacitance won't be too healthy for your rectifier in case of surges. Those caps could be also shorted. Second, check the tapping of your primary. You could be getting 110V from your wall, but tapping 100v in your primary. The AN mains is multi-tapped. Hope this helps. Enjoy the weekend
        
        Re: Thanks for suggestions. Any thoughts on - deankhor@singnet.com.sg 19:05:28 01/20/06 (3)
        
        In Reply to: Re: Thanks for suggestions. Any thoughts on posted by GTCharlie on January 20, 2006 at 17:45:07:
        
        I got this same problem a month back. The 5U4G glowed bright blue before fading off, and the 2A slow-blow fuse shorted. I opened up the chassis to find one of the 47uF cap blew. It's been a month since I replaced the fuse/cap....and I am still not sure what to make of the short.
        Hope this helps too. Have a great weekend.
        cheers
        
        Is blue light normal ? - Jean-Claude 06:07:35 01/22/06 (0)
        
        In Reply to: Re: Thanks for suggestions. Any thoughts on posted by deankhor@singnet.com.sg on January 20, 2006 at 19:05:28:
        
        Reading all your recent posts , I am wondering whether BLUE LIGHT in my KIT ONE are normal or not. It started by one 300B ,then the 6SN7 is also showing a blue light. I must add that I had a concenr with the C4 Jensen cap which cooked the R5 resistor...Since then the C4 is not connected anymore.
        Jean-Claude
        
        Will check caps and measure voltage - DougE 13:23:17 01/21/06 (1)
        
        In Reply to: Re: Thanks for suggestions. Any thoughts on posted by deankhor@singnet.com.sg on January 20, 2006 at 19:05:28:
        
        per your suggestions.
        I have rewired the driver board as Chris has, and yes the only blown fuses and rectifier tubes did come after this rewiring. However, I didn't touch the PS or rectifier boards when rewiring so I'm thinking that the only difference would be a surge as has been suggested. Will measure and see what's going on. Will check my winding tap as well. On a related note, the stock 5u4 did spark on turn on even before I rewired the driver board. So, I'm thinking this issue was there from first build. Of course, it could be something I've done since the original build has made it worse!
        As for the soft start, it sounds like the amount of surge that occurs shouldn't blow tubes--is that right? Anyone other than me and Chris blown a rectifier?
        Thanks again,
        Doug
        
        Re: Will check caps and measure voltage - scarebus 15:18:41 01/21/06 (0)
        
        In Reply to: Will check caps and measure voltage posted by DougE on January 21, 2006 at 13:23:17:
        
        Hi Doug,
        To clarify my incident on blowing the rectifier, the original
        5U4G sparked and blew way before hardwiring the system. I had some
        issues with the Cu caps and a Jensen, cooking R7 on psu. After hardwiring, on initial pwr-up, 5U4G(National tall bottle)
        glowed with blue light without blowing fuse nor cooking any resistors.
        On second pwr-up, with vom hooked to pin 4 or 6, voltage went up to
        around 700 with 5U4G glowing, but no smoke. Left it on, and saw voltage
        dropping gradually to around 200 and slowly came up to 425. And ever
        since, everthing is working fine.

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