AC Line Voltages, Then and Now

[Tom in N Texas]

Folks,

I've often thought that a good project would be a "Line Conditioner" in 
front of old equipment. It would have these functions, all in one box:

1)  Bucking Voltage reducer. Note that running a tube at high filament 
Voltage will significantly reduce its life The lower, the better, as long 
as the tube retains its design operating characteristics. Reliability of 
other components is reduced by excessive operating Voltage and heat.

2)  Soft-start device to limit the turn-on surge that reduces tube life.

3)  Line transient suppression.

4)  Filtering, in both directions and with common-mode suppression.

The filtering and transient suppression can reduce vulnerability to 
lightning and ElectroMagnetic Pulse (EMP).


Also:

a)  Replace tube rectifiers with plug-in semiconductor rectifiers. A 5U4 
rectifier pulls 15 Watts out of the filament transformer, and all of that 
heat has to be gotten out of the unit.

b)  Hang on an auxiliary fan(s), blowing through the ventilation holes.

All of these are easily reversible, to restore originality.


73 KC5INU Tom in North Texas

-------------------------------------------
At 01:02 AM 5/9/06 , you wrote:
>I recently became a bit concerned that my TX-1 Apache's power transformer 
>seemed to be running a bit hot: 47-49 degrees C.  Generally, I don't like 
>to see anything but tubes get hotter than 50 C, so this is pretty close to 
>the line.  The modulation transfomer runs a bit toasty at 45-47 C, but the 
>plate transformer runs cooler at about 38C.
>
>I notice also that the plate voltages are around 800VDC, instead of the 
>specified 750.
>
>As the older rigs were designed for 115 VAC, and we get about 123 VAC 
>coming out of the wall here (SDG&E just loves to push as much voltage as 
>they can through the lines), it's a fair chance the higher AC input might 
>be responsible.  I was wondering if:
>
>1. 47-49 C isn't too hot
>2. Could a "step-down" (there are many designs) to 115 VAC cool things off?
>
>...and, in the long run, is it worth it?
>
>Thanks to the group in advance,
>
>Lin/KJ6EF

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