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Author Topic: Removing Tubes From Ameritron 811H  (Read 7610 times)
K4EJQ
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Posts: 99




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« Reply #15 on: June 10, 2012, 08:05:31 PM »

And some wonder why W8JI doesn't hang around here much anymore!!!!! GEEEZZZZ  Bunky
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N4ATS
Member

Posts: 800




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« Reply #16 on: June 11, 2012, 01:13:42 PM »

No , the problem here is the poor old guy just wants to pull tubes out...He is wrapped around the ankles now since some folk have to be over technical.

I said this 5 times and its easy...

1) Unplug the amp
2) Wait a few hours
3) Pop the covers
4) Discharge the caps with a screwdiver to ground
5) Remove the darn tubes

Get over it people...

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W3DDF
Member

Posts: 74




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« Reply #17 on: June 11, 2012, 03:46:54 PM »

The tubes have been removed. Thanks for all the replies.  Let's move on...
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WB2WIK
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Posts: 20547




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« Reply #18 on: June 11, 2012, 05:33:01 PM »

Again....

That's why I put this in...

"If you REALLY are scared , take a screwdriver , rest it on the chassis and touch one tube cap with the tip of the screwdriver"

I agree, but it's best to place a resistor in series with the screwdriver to limit discharge current just in case the caps are fully charged...you can make a really big spark and potentially weld the screwdriver to the chassis without some current limiting. Wink

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W8JX
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Posts: 5488




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« Reply #19 on: June 11, 2012, 06:10:23 PM »


I agree, but it's best to place a resistor in series with the screwdriver to limit discharge current just in case the caps are fully charged...you can make a really big spark and potentially weld the screwdriver to the chassis without some current limiting. Wink


"IF" they were fully charged, the meter would reflect it. (you would also have either all your bleeder resistors open or unit still on)
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W1QJ
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Posts: 1443




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« Reply #20 on: June 11, 2012, 10:59:45 PM »

If I discharge an amp that has been "ON" once a day, I do it fifty times!!!  I turn the amp on I see the HV meter read HV, I turn it off I see the HV bleed down on the meter, the meter reads zero, I take a long insulated screwdriver and short anode of tube, plate choke, to ground.  A very minor spark if any after the meter reads zero.  If I turn an amp on and the HV does not read, now you have to stop and think and be  really careful. 
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W8JX
Member

Posts: 5488




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« Reply #21 on: June 12, 2012, 07:01:42 AM »

If I discharge an amp that has been "ON" once a day, I do it fifty times!!!  I turn the amp on I see the HV meter read HV, I turn it off I see the HV bleed down on the meter, the meter reads zero, I take a long insulated screwdriver and short anode of tube, plate choke, to ground.  A very minor spark if any after the meter reads zero.  If I turn an amp on and the HV does not read, now you have to stop and think and be  really careful. 

I agree that a screw driver is a very good method to make sure. No reading at all on HV meter at any time does indeed present a new "challenge".
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KE3WD
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Posts: 5694




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« Reply #22 on: June 12, 2012, 07:13:04 AM »

The tubes have been removed. Thanks for all the replies.  Let's move on...
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KH6DC
Member

Posts: 634




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« Reply #23 on: August 08, 2012, 06:15:31 PM »

Irregardless you should short the leads of the filter capacitor(s) with an insulated tool like a screwdriver or insulated long nose pliers.
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73 and Aloha,
de Delwyn, KH6DC
K0IZ
Member

Posts: 737




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« Reply #24 on: August 09, 2012, 06:28:00 AM »

Put the tubes back in, so you can remove them correctly !

Seriously, I have over 50 years of ham radio building experience, and ALWAYS short out the high voltage before touching anything.  99.9% of the time the circuit (bleeders, etc), has taken care of the voltage.  But I'd rather not place my faith (and life) on some resistors being good.  Even a small remaining voltage can cause a violent physical movement, causing a hand to be gouged on a chassis, a dropped amp, etc.   Only takes a second to short to chassis with a screwdriver.   Cheap insurance.
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G3RZP
Member

Posts: 4393




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« Reply #25 on: August 09, 2012, 09:10:25 AM »

K0IZ,

Doing that is probably why you have managed over 50 years of ham radio building experience!
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N4JTE
Member

Posts: 1154




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« Reply #26 on: August 09, 2012, 04:56:43 PM »

Best advice, besides the obvious stuff, was to grab the tubes from the bottom when removing. Sorry
Tom, but those tube sockets are REAL easy to dislodge, I know the design budjet contraints but be gentle with the sockets.
Bob
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KB5ZSM
Member

Posts: 70




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« Reply #27 on: August 12, 2012, 12:33:38 AM »

Do NOT short directly to ground!!! Use a current limiting resistor in series so as not to damage the capacitors. Too much current through a capacitor can ruin a perfectly good cap.
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KC4MOP
Member

Posts: 729




Ignore
« Reply #28 on: August 12, 2012, 06:00:42 AM »

Put the tubes back in, so you can remove them correctly !

Seriously, I have over 50 years of ham radio building experience, and ALWAYS short out the high voltage before touching anything.  99.9% of the time the circuit (bleeders, etc), has taken care of the voltage.  But I'd rather not place my faith (and life) on some resistors being good.  Even a small remaining voltage can cause a violent physical movement, causing a hand to be gouged on a chassis, a dropped amp, etc.   Only takes a second to short to chassis with a screwdriver.   Cheap insurance.
You took the words right out of my keyboard.
I never considered that discharging an HV supply as an option or if I was scared. It was part of being a qualified Electronic Technician.
Fred
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