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Old 13th January 2013, 02:15 AM   #1
banaca is offline banaca  Canada
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Default Kt88 Pin alignement problem=did a mistake= HELP NEEDED

Someone sold me a Amp ( Quicksilver V4) with a set of JJ kt88 . Some of the central pins of the tube are missing ... ( the plastic guide in the middle) I instaled the the tubes, but I think a mis- aligne a tube... Now my amp don't bias. I've broken my wonderfull amp... Can someone tell me the problem ( a capacitor? , a resistor is damaged? )

Last edited by banaca; 13th January 2013 at 02:36 AM.
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Old 13th January 2013, 02:48 AM   #2
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Identify the correct orientation for the tube, re-install it, and see if it works.

Quote:
Originally Posted by banaca View Post
Someone sold me a Amp ( Quicksilver V4) with a set of JJ kt88 . Some of the central pins of the tube are missing ... ( the plastic guide in the middle) I instaled the the tubes, but I think a mis- aligne a tube... Now my amp don't bias. I've broken my wonderfull amp... Can someone tell me the problem ( a capacitor? , a resistor is damaged? )
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Old 13th January 2013, 02:50 AM   #3
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by banaca View Post
Someone sold me a Amp ( Quicksilver V4) with a set of JJ kt88 . Some of the central pins of the tube are missing ... ( the plastic guide in the middle) I instaled the the tubes, but I think a mis- aligne a tube... Now my amp don't bias. I've broken my wonderfull amp... Can someone tell me the problem ( a capacitor? , a resistor is damaged? )
I would suspect the tube. Can you swap the KT88s with another amp (assuming you have two mono blocks)?

If the problem follows the tubes than you know what you need to do.
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Old 13th January 2013, 03:01 AM   #4
banaca is offline banaca  Canada
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I did change the tubes ( I had a extra quad) The amp will not bias anymore. It only goes to 20ma ( it is supposed to go up to 45-50ma) I did check my slow blow fuses, the inputs tubes... still a problem... My other mono is ok btw.
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Old 13th January 2013, 04:18 AM   #5
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A schematic is required.
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Old 13th January 2013, 10:40 AM   #6
banaca is offline banaca  Canada
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I've emailed Mike Sanders , the guy who build it, ( about another amp) I told me , there is no shematics for is amps ( including mine) the V4
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Old 13th January 2013, 10:43 AM   #7
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Hi!

Best is to consult the person who built the amps. He should know best what the problem might be and he would also be the best person to repair it

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Old 13th January 2013, 11:24 AM   #8
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Without a scematic it will be mostly guesswork.
So let's see if we can guess in the right direction...
Do you know how the KT88 was oriented? One, two,... pins (counter)clockwise? Perhaps we can deduct what might have happened.
With the powercord and the KT88's removed, can you measure the resistance of pins 1 & 8 (the ones next to the locator notch) to ground? Comparing that to the resistance in the good amp will tell you if there is a problem with the kathode resistors (assuming there are kathode risistors).
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Old 13th January 2013, 03:00 PM   #9
banaca is offline banaca  Canada
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Quote:
Originally Posted by Parafeed813 View Post
Without a scematic it will be mostly guesswork.
So let's see if we can guess in the right direction...
Do you know how the KT88 was oriented? One, two,... pins (counter)clockwise? Perhaps we can deduct what might have happened.
With the powercord and the KT88's removed, can you measure the resistance of pins 1 & 8 (the ones next to the locator notch) to ground? Comparing that to the resistance in the good amp will tell you if there is a problem with the kathode resistors (assuming there are kathode risistors).

Great info ' thanks! It was almost a the right aligment. But I can not say counter or clockwise.... I will have the amp check by a tech. But I will tell him want you just said about the kathode risistor . Thanks!
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Old 13th January 2013, 03:06 PM   #10
jrenkin is offline jrenkin  United States
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My guess, since you CAN bias to 20mA, is that the bias pot is the problem, or one of the other resistors in the bias circuit. Maybe check those.
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