[ARC5] [Milsurplus] RAK question and RAL

[Kenneth G. Gordon]

On 25 Dec 2017 at 20:03, Bruce Gentry wrote:

> The 876 ballast was called a "Barretter" tube by RCA. It has an iron 
> filament and is filled with hydrogen under pressure, it gets blazing hot 

You can say that again!

> so it needs to be in a chimney enclosure of some sort or the glass will 
> be strained and it will shatter- quite loudly.

Hydrogen in air is explosive. And the RAK/RAL power supplies do have a chimney of sorts. 
The 876 is mounted in the exact center of the power supply, facing the back and is centered 
in a chimney of sorts.

> Some early AC powered 
> entertainment receivers that had direct heated filaments used the 876 to 
> protect the tubes from voltage surges. The tube is used in a highly 
> inefficient "brute force" circuit where most of the power goes to the 
> resistor in series with the tube and the power transformer in paralell 
> with the resistor  just "goes along for the ride".

Yes. For OUR purposes, a total waste of power and a source of unneeded heat.

>  I had an RAK and RAL 
> (which I very foolishly traded away), and  put a piece of fiber 
> insulation under the center contact of the 876 after setting the switch 
> to unregulated. I wanted to keep the tube in place for novelty and 
> completeness of the power supply. Please do check the voltages in the 
> power supply to see if today's 120 or more line voltage is too much even 
> with the transformer taps set at their highest.  I have not yet seen a 
> regenerative receiver that works as well and is as easy to control the 
> regeneration as these.

And I completely agree with you. In my opinion, the RAL is the very best HF regen I have 
ever used, and the RAK is excellent at MF and VLF too.

> They may be archaic, but can be a very nice 
> surprise.

As I've said before, I used my RAL-7 for something like 12 years as my only station receiver. 
My ONLY complaint with it was the frequency readout, which was essentially non-existent. 0 
- 10 and 0 - 100.

Other than that, it simply sat there and always worked.

I turned it off after about 8 years to check the tubes, found nothing wrong with them, so I 
turned it back on and left if.

It has a certain "transparent" sound to it, like you are directly connected to the RF spectrum 
with nothing in between you and the stations you are working.

I only wish it wasn't quite so big.

Ken W7EKB

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