[ARC5] Receiver AC Power Supplies - lower voltage B+

[Kenneth G. Gordon]

On 13 Dec 2014 at 10:20, DSP3 wrote:

> Tell you what Mike... I've not seen (but not tried, either) on the 
> National but I have noticed that exact phenomena on ARC-5/274-N 
> receivers at about 160v or so B+.  Curious???
> 
> Jeep - K3HVG

I discovered some time ago that MY "ARC-5" receivers "seemed" to work 
much better at 170 - 180 VDC. 

I concluded that +170 VDC was optimal and mentioned that fact here some 
time ago, when the discussion at the time concerned running them at lower 
voltages...down to +24 VDC.

At the 170-180 VDC level, they were both far cooler, and, what to me was 
more important, FAR quieter. S/N ratio appeared to be very noticeably 
improved.

I also found that, when doing this, increasing the screen voltage on the 
RF and IF amps to 170 VDC also made a huge difference in operation. All 
that takes is moving one wire from the junction of R-22 and R-23 to the 
"hot" end.

I did not experiment with attempting to find the optimal relationship 
between plate and screen voltages, although I'll bet there is such.

The only side effect from using the lower voltage was about 1/2 the 
normal audio output level.

YMMV.

Ken W7EKB