Heater wire voltage too low

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tubenit
Junior tube assistant
Posts: 57
(4/5/04 7:21 am)
 Heater wire voltage too low
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 The heater wire voltage on my Dano Centurian is 5.9 volts AC on the lamp (which is the first connction from the power transformer) and the same on all tubes. The amp sounds great (like a shrunk down '59 Bassman) but I know the voltage should be 6.3 volts. I can not find any reason for the low voltage tracing everything over. Voltages on all tube plates and ma bias seem to be reasonably within specs.

The PT has no 5 volt for a rectifier. The heater wires do run to a 6X4 rectifier. There are 2 CTs on the PT one being for the heater wires.

Is this most likely a weak power trans? OR should I be looking for some other cause?
If it is a weak PT would there be significant concern that the lower heater voltage would damage other amp components? Any help would be appreciated.
Thanks, tubenit


Edited by: tubenit at: 4/9/04 6:05 pm
 
Tiny Daddy
I will work on all amps
Posts: 605
(4/9/04 8:46 pm)
 Re: Heater wire voltage too low
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 This is nothing to worry about. 5.9V will not do any harm.
 
Leevi
Junior tube assistant
Posts: 133
(4/10/04 9:32 am)
 Re: Heater wire voltage too low
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 I have noticed that the heater voltage is often too high close to 7V, I have measured even higher values. What does this cause?
/Leevi
 
Tiny Daddy
I will work on all amps
Posts: 609
(4/10/04 9:49 am)
 Re: Heater wire voltage too low
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 If the heater gets too much voltage the coating that emits the electrons gets damaged and tube life may be very short.
 
ganzonimx
Hey get your own solder
Posts: 459
(4/10/04 10:02 am)
 Hetaer voltage
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 I always have the heater voltage on the higher side (wall voltage 127 - 130V).

My Electro-Harmonix and Svetlana Tuba Data Sheets states a heater voltage min 5.7 ans max 6.9VAC.

I recently dropped the heater voltage from 7.1 to 6.4 V with two paralleled/reversed 6A diodes - works very nice!

Cris.
 
Tiny Daddy
I will work on all amps
Posts: 610
(4/10/04 11:37 am)
 Re: Hetaer voltage
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 Diodes work better than a resistor because you will still get about the same voltage drop with different currents or number of tubes. You could use a bridge and bolt to the chassis for heat sinking but remember a 10 amp bridge should have 5-amp diodes.
 
tubenit
Junior tube assistant
Posts: 58
(4/11/04 6:10 am)
 Re: Hetaer voltage
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 Thanks for the reply! It is greatly appreciated! The amp sounds great but I had never seen any heater voltage that wasn't 6.3 so I did not know what to make of it (only my 4th amp to re-do). With respect, tubenit
 
 
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