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#1 2013-01-21 19:17:34

RosewoodMusic
New member
Registered: 2013-01-21
Posts: 3

72 V4 Tubes will not light.

I have got in a V4 that was doa checked out the power transformer was dead got the replacement from FT.net It reads to spec but when hook out the filament 6.3V by its self they will not light any enlightenment would help me out a great deal.

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#2 2013-01-21 20:43:17

hangman
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From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: 72 V4 Tubes will not light.

A few questions:

Do you measure 6.3 volts on the tube sockets? 

If not
Are the tubes new or old.   Could be that your filaments Are smoked.


If not... Remove the hum balance pot and measure again (it could be shorted)

I would guess it is one of those two things.

-Steve

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#3 2013-01-21 22:33:03

RosewoodMusic
New member
Registered: 2013-01-21
Posts: 3

Re: 72 V4 Tubes will not light.

Tubes are old but test good I get 6.3v before connecting them to sockets then drops to nilll thanks. I will look in the Hum Balance pot.

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#4 2013-01-21 22:55:16

RosewoodMusic
New member
Registered: 2013-01-21
Posts: 3

Re: 72 V4 Tubes will not light.

Ok got it removed 3 wires of hum balance they they lit up thanks for the help we had removed them before but maybe in our chain of sequences had something else not done right at the time thanks for your help.

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#5 2013-01-22 07:58:04

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: 72 V4 Tubes will not light.

Did your new transformer have a center tap on the filament winding?   The hum balance pot does need to be in there... Or you could replace it with a couple resistors.   
The amp will have a nasty hum without it.

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