Re: Drake R4B 115VAC Operation

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Another, less expensive solution, would be to use a 20A, 10V transformer off the AC line, and hook the secondary in a BUCK fashion to lower the 120-125 volts to around 110VAC.? There would be less likely hood of someone cranking up the variac fully clockwise!? My variac can output up to 140VAC which I find useful at times but it would likely damage a 110VAC piece of equipment if left there for too long.

Clint, VE3CMQ

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From: [email protected] <[email protected]> On Behalf Of VE7PS via groups.io
Sent: Friday, 24 November 2023 10:28
To: [email protected]
Subject: Re: [DRAKE-RADIO] Drake R4B 115VAC Operation

Bill:

I will add my $.03 Cdn to this discussion as well.

I run (most) of my Drake B and C-lines off Variacs set for 110 VAC. Doing so reduces heat for sure but also output power is lower and as these stations are run into tube amps (L4B/L-75/L7) I find it's easier?to control the drive power to the amplifiers running them at this?level.? Some of these radios have been in my shack for well over 20 years now, and I have?never had to replace a 6JB6 in any of them once they were set up in the beginning?back in the mid-90's.? In fact I've never changed any? tube in any of them after their initial inspection/restoration that I recall, with one notable exception...the noisy 3rd mixer in the R-4C.

I do the same thing with the S-line and the Kenwood Hybrids.? Some of the Kenwood Hybrids seem to "enjoy" running at 110 VAC while the "youngest one" ...the TS-830s does not, as output power on that one drops considerably on that one, especially on the higher bands.? ? That could well be soft 6146's or driver tube I know, but have yet to investigate that further.

The Drake 5 and 7 lines run on full line voltage, but then they are all powered through a regulated low voltage power supply so it's a bit of a different ballgame there.? The two? "modern rigs" (all solid state) that I have run on full line voltage.? Hmmm...the newest of those is now almost 20 years old!!!!? ?The other one is now over 30 years old...not very "modern" I know.? I am treating myself to one more brand new radio and amplifier....but the decision on what it will be has yet to be made.? Not an easy choice these days....they all have something to offer it seems.

I am fortunate here that my line voltage runs at just over 120 VAC...about 121-122....and I've never seen it vary much from that, unlike some others. Power outages are quite rare (as are thunderstorms)......maybe? 2-3 bumps per year,?and long outages have only?occurred twice in 17 years here after huge windstorms dropped thousands of trees.? For these older radios I just think it's good practice to run them at around 110 VAC.

YMMV!

Peter

VE7PS

On Fri, Nov 24, 2023 at 7:40?AM David <david.w5xu@...> wrote:

Bill:? You have opened up a very large door here.? If the radio (this is a BIG if) was designed when the standard voltage was 115V (by law and practice) , then the radio was DESIGNED to be used at that input voltage.? The standard today is 120V.? Your voltage now may be +- several % from this actual design?voltage. Looking at the radio manual will generally tell you what the input design voltage is.

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The short?issue here is that if you run a radio beyond the designed voltage (with the?+- included), then your radio is not running as designed.? So, what does this mean?? ? Let's take filaments on the tubes as an example.? Tube manufacturers?use?+- 5 to 10 % on this number.? So, if at the voltage you are plugging into is within that range, filament wise you are likely ok.

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MAny of these radios are transformer?powered.? So the B+ voltage (for the plates of the tubes, generally, the higher the input voltage, the higher the plate voltage.? For the most part the ratings of the rectifier diodes and capacitors are generally?ok with this.? But take the plate voltage of the 6EH5 tube in the Audio output of the R4 thru R4B radios has a 150 volt max rating.? Measure this and you will see that this voltage is greatly exceeded.? Ever wonder why you changed so many of these?

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So, the list can go on.? It becomes a real issue when you are dealing with older radios that were designed for the then standard of 110 Volts AC.? Now operating at 120 volts nominal, is a large % of overvoltage.? ?

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The last factor is where your particular voltage source is generated, transformed and ultimately delivered to your service.? For me, my voltage at any given?time is generally between 123 and 126 volts.? THis is dependent on the primary voltage load and the individual load of your service.

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So, while it is nice to see that you take, for especially the?older radios, some care and place them on the variac, it is not a common practice?to run these radios on this rating thru the variac forever.? So, your question was real.? The short answer is yes, but the practical answer is no.

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Welcome to the world of Older radios.? It is FUN!

David Assaf III

W5XU, VP8RXU

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On Fri, Nov 24, 2023 at 9:13?AM N3WM - Bill via <n3wm=[email protected]> wrote:

Please, is there any advantage to running the R4B receiver on a VARAC for 115Volts?? Maybe less heat I'm thinking...

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Thanks,

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Bill N3WM

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