[Amps] Trio TL-922 Filament Transformer...

[Will Matney]

Ott,

It's not good to do this as the unbalance will cause the transformer to 
heat up as it's doing. Remember when there's a voltage drop, there's a 
current rise. Any increase in the electrical current of the coil 
directly causes an increase in the magnetic current and thus more heat. 
The current increase is caused where the load resistance will be lower 
due to the tubes heater not getting hot enough. The tubes spec sheet 
will give the recommended voltage and what current it will run at. This 
is where it should be ran and the transformer will not run as hot. The 
spec sheet will give a minimum, recommended, and maximum heater voltage. 
If you would want to run it at a slightly lower voltage, the transformer 
needs to be sized for this current increase. Hope this helps.

Will Matney


r391 wrote:

> Tonight I decided to pull some PM on my Japanese Trio TL-922...
>
> Filament voltage 4.8 volts... at the tube pins... thought hmmm... 
> better a little low than a little high?
>
> Felt the filament transformer and it felt quite warm after only 5 
> minutes or so of operation...  this is the first time I've done this 
> so I don't know how warm the transformer should feel after 5 minutes 
> so...
>
> Out of curiosity I decided to check mains input voltage to the 
> filament transformer and it was 122 volts on one leg and... 102 volts 
> on the other so that the two primaries input voltages are unbalanced 
> to each other by 20 volts...
>
> Thinking "that can't be right" as the schematic shows "0" to "0" and 
> "120" to "120" between the two transformers so that  their both shown 
> to be phased the same way and that my 122 volt line voltage should 
> appear on all of the primary windings equally... I decided to trace 
> the wiring.
>
> Found the installed wiring different from the schematic...  this 
> difference is either from the factory or by previous owner design but 
> is such that one of the 120 volt lines from the filament transformer 
> is connected to the 100 volt connection on the HV transformer thus 
> feeding one of the filament transformer primaries 100 volts instead of 
> 120 volts while the other primary was connected to the 120 volt 
> connection on the HV transformer and receiving 122 volts...
>
> Was wondering if this is a factory wiring error or a deliberate 
> attempt by the factory or a previous owner to adjust the filament 
> voltage... anyone seen this before?
>
> tnx, Ott
>
>