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Author Topic: Preparing NOS GU74  (Read 1538 times)
N4RSS
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Posts: 258




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« on: August 22, 2010, 11:11:27 AM »

I have a QRO 2500 for which I just ordered some spare tubes.  The amp has a separate filament transformer.

I'm wondering if it would be worth it to disconnect the HV supply and run just the filaments to prepare the tube.

Edit:  would the amp even turn on if I did this, don't know

Is this even possible with this amp and would it be worth it ?

N4RSS
« Last Edit: August 22, 2010, 11:24:17 AM by Roger Steffens » Logged
W8JI
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Posts: 9304


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« Reply #1 on: August 22, 2010, 11:29:37 AM »

I have a QRO 2500 for which I just ordered some spare tubes.  The amp has a separate filament transformer.

I'm wondering if it would be worth it to disconnect the HV supply and run just the filaments to prepare the tube.

Edit:  would the amp even turn on if I did this, don't know

Is this even possible with this amp and would it be worth it ?

N4RSS

Any metal ceramic tube has to getter from filament heat. If you are unsure of tube gas, run it several hours with filament AND blower only.
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N4RSS
Member

Posts: 258




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« Reply #2 on: August 22, 2010, 11:39:20 AM »

Thanks.

I guess I can just disconnect the HV connector at the tube top, not unplug the xfmr altogether, is that correct ?
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K0ZN
Member

Posts: 1543




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« Reply #3 on: August 22, 2010, 01:37:14 PM »

Hi.

I am not familiar with your amp; do you have a "stand by/operate" switch?? If so, it MAY allow operation with only filaments and blower on
in the "stand by" position.  If not, then I guess you do have to go inside and unhook some stuff. A check of the Owner's Manual is also
probably worth the effort.

BE SURE YOU ARE CAREFUL, fully UNPLUG from AC Power, and make sure the filter caps have fully discharged, etc. before doing any work.
As I am sure you are aware, the voltages and currents in that amp "are the real deal" when it comes to safety.

73,  K0ZN
« Last Edit: August 22, 2010, 01:41:34 PM by Jon M. Pollock » Logged
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