[Milsurplus] USS Slater DE-766

[Kenneth G. Gordon]

On 21 May 2020 at 15:22, Steven Syrotynski wrote:

> Hello out there, my name is Steven Syrotynski  W2TRH and i am one of the 
> volunteers in the radio room on the museum ship USS Slater here in 
> Albany  N.Y. We have some RAK,S and an RAL. One has a power supply that 
> is missing it's 80 Ohm snap in resistor that is next to that giant 
> ballast tube :), and the other one needs a power supply as well. Does 
> anyone have any of these around for sale, please let me know at 
> ssyrotyn at nycap.rr.com, below is a link to the ships web site, thank you 
> for your time,
> 
> Steve
> 
> https://ussslater.org/index.php

As a long, long-time user of both the RAL and the RAK, I agree with Bill Cromwell, and can 
state categorically that you do NOT need the dropping resistor nor the ballast tube. In fact, 
the power supply has a switch down low, inside, which completely disconnects those. As I 
remember it, that switch is just under the heat-shield for the ballast tube or resistor.

Using those causes a power drain of around 300 watts and much greater heat output. 
Without them, the power drain is less than 100 watts.

You only need those if the receivers are being used on a combat ship, while that ship is in 
combat, with the turrets swinging around and other very heavy uses of the AC power.

When using "shore power" you most certainly do not need them. Turn them off. The heat 
will be far less and the power supplies will last longer.

As far as a power supply for the one missing, the power requirements for the RAL/RAK are 
very modest: there are only 6 tubes in either receiver. There is a plate on the front of each 
receiver which lists the power requirements.

Temporarily, you can build a simple supply which will do the job. Normally, one needs 180 
VDC at 35 mA, 90 VDC regulated at 1 mA (!) and 6.2 V AC/DC at 2 amps. My home-built 
power supplies use a VR-90 for the regulated voltage, and those power supplies are far, far 
smaller, and at least as reliable as the original ones.

The 90 V Regulated is for the regenertive detector to help prevent drift. In point of fact, the 
way the receiver is wired internally, you only need the filament voltage and 90 to 180 VDC 
input to the 180 VDC connection as internal resistors and wiring feed the detector if the 90 
V regulated is missing.

The receivers are also designed specifically to run from a battery supply providing only 
filament voltage and 90 to 180 VDC.

They are very, very good receivers, very stable, quite sensitive and unusually selective.

I consider the RAL to be the finest HF TRF receiver I have ever used. An RAL-7 was my 
main station receiver for around 12 years, beginning in about 1960.

Ken W7EKB