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  1. #1

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    Unhappy Help with Shorted Tube

    My tube fuse (1/2 amp fast blow) of right channel keeps on blowing. I checked the manual and it says i should check if the red led is not light then that tube is blown.
    But the problem is non of the LED is on as there is no bias current because of blown fuse.
    Then how do i go about finding which of the tube is shorted.

    BTW its a Cary Tube Amp. Its has Quad El-34's for each channel. The left channel is good but there is the a problem with the right channel.
    Here is the link to the amp specs http://www.caryaudio.com/products/audio/cad280sa.shtml

    I'm very new to tubes so excuse me if i have said anything incorrectly.

    What's the best way to find out which tube is shorted so that i don't keep on blowing fuse. So far I have blown 3 fuses.

    Please help..........
    Last edited by malikarshad; 11-06-2005 at 12:57 AM.

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
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  2. #2

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    Does the LED light up after replacing the fuse?

    Try swapping the left tubes for the right. If the fuse blows on the same side again, it's most likely the amplifier.

    Is it still under warranty? Try to contact Cary Beautiful amp btw. Hope you find the problem soon.

    If you know any techies that are good with tubes, bring it to the shop. Trial and error is no fun especially when you have 12 power tubes to deal with(too much $$$).

    Maurice
    CD Player: Original CD-A8T
    Pre: Antique Sound Lab Passive T1-X DT
    Amp: NAD C270
    Speakers: B&W DM6
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**

  3. #3

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    Question

    Quote Originally Posted by organ
    Does the LED light up after replacing the fuse?
    Maurice
    No the LED's does not light up at all. I have also tried to adjust the bias for the RC but nothing happens. The fuse blows everytime I turn the amp on so I don't get a chance to do anything with the bias.
    I think I will try swapping the tubes from LC to RC.
    BTW how do i remove the tubes? Just pull it out!!!

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  4. #4

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    The EL34's can be a little tight depending on the tube sockets used.

    First, get a good grip on the base of the tube (the hard plastic part). Use your other hand and start wiggling/pulling slowly from the top of the tube. They should come out very easily like this.
    CD Player: Original CD-A8T
    Pre: Antique Sound Lab Passive T1-X DT
    Amp: NAD C270
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    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**

  5. #5

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    Actually, before swapping tubes. Check every tube on your right channel. Make sure none of them have burnt marks or look strange.
    CD Player: Original CD-A8T
    Pre: Antique Sound Lab Passive T1-X DT
    Amp: NAD C270
    Speakers: B&W DM6
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**

  6. #6

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    Quote Originally Posted by organ
    Actually, before swapping tubes. Check every tube on your right channel. Make sure none of them have burnt marks or look strange.
    Little late but I went ahead a swapped the tubes and again the tube fuse is blown. I don't have any more fuse now. I'll have to wait until morning.

    BTW does the burnt marks indicate that the tube is out?

    The amp also has 2xEL84s and 2x12BZ7. Could these also cause a problem?

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
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    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
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  7. #7

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    Man, sorry to hear about that.
    If the tube was shorted, you're likely to see burnt marks in the glass if there were sparks with high voltage.

    It could be the small driver tubes but hell, it could be anything. So far, I'm guessing it's the amp. If it blows again tomorrow, you should get it repaired.
    CD Player: Original CD-A8T
    Pre: Antique Sound Lab Passive T1-X DT
    Amp: NAD C270
    Speakers: B&W DM6
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**

  8. #8

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    i checked all the tubes and there are no burnt marks or anything unsual from outside. checked all the amp fuses and they are OK.

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  9. #9

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    Unhappy

    Anybody any thoughts. I've got this great amp and I cannot use it.
    Please guys let me know..... :(

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  10. #10

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    You could pull all the tubes out and see if the fuse still blows. That would tell you there is something wrong on the inside of the amp. Good place to start.
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D

  11. #11

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    Unhappy

    Quote Originally Posted by madmax
    You could pull all the tubes out and see if the fuse still blows. That would tell you there is something wrong on the inside of the amp. Good place to start.
    madmax
    Thanks for the advice. I'll try that.
    Damn these amp has 12xEL34.
    Is it necessary to replace all 12 if one is blown. The tubes are EL34 BSTR. What brand is that?

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  12. #12

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    I don't think so. Each one probably has an adjustment to set the bias so they don't have to be matched. It would be a good idea to get the same brand as it has. If they have a marking on them like "34", "35", any two numbers like that you can order a single of the same value at www.thetubestore.com or other places.
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D

  13. #13
    Old Polk
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    Quote Originally Posted by malikarshad
    The tubes are EL34 BSTR. What brand is that?
    I believe they're Ruby tubes. Popular in guitar amps.
    Be-Bop-A-Lula, Baby What I Say

  14. #14

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    Question

    Quote Originally Posted by BlueMDPicker
    I believe they're Ruby tubes. Popular in guitar amps.
    Yes they are Ruby tubes. Do you know where to buy it or can i replace it something similar that will match the rest of the EL34 BSTR's

    Quote Originally Posted by madmax
    I don't think so. Each one probably has an adjustment to set the bias so they don't have to be matched. It would be a good idea to get the same brand as it has. If they have a marking on them like "34", "35", any two numbers like that you can order a single of the same value at www.thetubestore.com or other places.
    Yes there are no. 31 and 32 on them.

    I tried removing all the tubes & turning on the amp. The good news is :) the fuse does not blow.
    The bad news is how do i find out which ones of the 12 tubes is shorted?
    Do you think I should put one tube at a time a check if the tube blows? I'm not sure about it. Can somebody tell if I can do that?

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  15. #15
    Old Polk
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    You can get the tubes here .

    Put your tubes in in pairs, one per side, starting at the back. Turn all your bias pots all the way down. Power up with each pair until you encounter the fuse issue. Now you have it down to 1 of 2 tubes.

    The amp will probably play with a pair missing at lower power. Order two new ones.

    Are you sure you do not have a short at the speaker binding posts?

    Edit - Oh yeah, don't forget to re-bias your tubes.
    Be-Bop-A-Lula, Baby What I Say

  16. #16

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    Actually, do you know how to bias the tubes? Don't take that as a put down if you do, its just that you said you were new to tubes. :)
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D

  17. #17

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    Quote Originally Posted by madmax
    Actually, do you know how to bias the tubes? Don't take that as a put down if you do, its just that you said you were new to tubes. :)
    madmax
    Well I read the manual first. It was when I was setting the bias I ran into the fuse problem. I can set the bias individually for each channel.
    I was able to set the bias on one channel but the fuse always blows out even if the bias is turned to the minimum.
    But thanks for asking

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  18. #18

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    Thumbs up

    Quote Originally Posted by BlueMDPicker
    The amp will probably play with a pair missing at lower power. Order two new ones.
    Man thanks a lot for your advice :) . I was able to find a bad tube. Do I have to buy the same brand or any brand is ok as long as they match
    The tubestore.com lists Shuguang EL34B as Ruby EL34BSTR.
    Thanks all for your valuable advice. It was really an experience troubleshooting the problem.

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  19. #19

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    It might be the bias. Make sure you start with both bias pots on minimum. As you decrease one channel, the other will increase and vice versa. You have to increase one channel a little, check the other channel and increase it. Doing it slowly is the best way.

    The EL34BSTR are from Ruby tubes. Ruby purchased from Shuguang which are made in China and put their logo on the tubes. Do they look like these? http://www.thetubestore.com/shuguangel34b.html I have a quad of Shuguang EL34B and they sound like SS to me.

    Maurice
    CD Player: Original CD-A8T
    Pre: Antique Sound Lab Passive T1-X DT
    Amp: NAD C270
    Speakers: B&W DM6
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**

  20. #20

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    Quote Originally Posted by organ
    It might be the bias. Make sure you start with both bias pots on minimum. As you decrease one channel, the other will increase and vice versa. You have to increase one channel a little, check the other channel and increase it. Doing it slowly is the best way.

    The EL34BSTR are from Ruby tubes. Ruby purchased from Shuguang which are made in China and put their logo on the tubes. Do they look like these? http://www.thetubestore.com/shuguangel34b.html I have a quad of Shuguang EL34B and they sound like SS to me.
    Maurice
    Maurice you are right on. That was exactly the problem & finally I hope its fixed.
    Yes the tube looks like the one in the link. Are you thinking of rolling out those tube than I might be interested. Let me know. ;)

    Speakers- Salk SongTowers, C-SongCenter,Surr-SongSurronds1, Lsi7
    PreAmp,Amp - Integra DTC-9.8, Outlaw 770 (SC A2 IC)
    DVD - Oppo BDP-93,HD-A35
    Sub - SVS Pb2+(12.3 drivers)
    Screen- JVC HD-250 projector w/122" DIYscreen
    TV- Sony 32" XBR6
    2channel
    Logitech SqueezBox Duet w/ FLAC
    Tube Gear - Cary Audio Tube Amp (280SAV-12r)
    Compter-Music
    Speakers - Onix 0.5 ref, Sub Infinity PS10 (250 watt)
    Receiver - Denon AVR-3803


  21. #21

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    Remember to increse the bias slowly over a period of 30 mins or more. Only when the amp is fully warm will the bias stabalize. Also, keep checking it throughout the day/night because it will drift along with your incoming AC from your wall. My amp is made to be biased at 1.56DCV but will drift 0.1V so I like to keep it around 1.46V.

    I don't plan to use my Quad of Shuguangs EL34B's again. So if you're interested, PM me.

    Maurice
    CD Player: Original CD-A8T
    Pre: Antique Sound Lab Passive T1-X DT
    Amp: NAD C270
    Speakers: B&W DM6
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**

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