[ARC5] A.C. Modified BC-348

[Michael Hanz]

Less expensive transformer with one less winding, same standard 
transformer design.

And, thePS runs cooler:

Filament power dissipation:

5Y3   -  10.0 watts
25Z5 -    7.5 watts

Not too much mystery in that kind of evolution...

Mike - KC4TOS

On 8/28/2021 1:27 PM, J Mcvey wrote:
> Sure, that's a standard transformer isolated design using a 5Y3.
> Safe as it gets.
> I would like to see why they used a 25Z5 on the other setup.
> Makes one go hmmmm....
>
> On Saturday, August 28, 2021, 12:52:12 PM EDT, Rich Post 
> <kb8tad at gmail.com> wrote:
>
>
> Mike is correct relative to the ease of use of the 25Z5 with a 
> transformer designed for directly powering the BC-348 filament string 
> at 24-28 volts. The instruction sheet says Signal Corps.  Did 
> Hallicrafters produce both an Army version and a Navy version?
>
> My EP-298 power supply uses a 5Y3 rectifier and has the Navy 
> acceptance stamp.
> <https://people.ohio.edu/postr/bapix/BC348Q_3.htm 
> <https://people.ohio.edu/postr/bapix/BC348Q_3.htm>>
>
> Rich KB8TAD
>
>
> On Sat, Aug 28, 2021 at 12:08 PM Michael Hanz 
> <aaf-radio-1 at aafradio.org <mailto:aaf-radio-1 at aafradio.org>> wrote:
>
>     Schematic attached.  There were apparently two different rectifier
>     tubes used in the EP-298 Halli supply - initially a 5Y3GT, then a
>     6X5GT-G - which has a separate cathode independent of the
>     filaments.  It is not hard to anticipate the eventual substitution
>     of a 25Z5 to eliminate the filament winding in the transformer...
>
>     No "safety" issues with that design.
>
>     On 8/28/2021 10:41 AM, J Mcvey via ARC5 wrote:
>>     A 25Z5 implies a "series string/ hot chassis circuit.
>>     The BC348 design does not lend itself very well  to a
>>     transformerless power supply.
>>     Then again, Hallicrafters was famous for grounding one side of
>>     the AC supply to the chassis!.
>>     This kind of mod is unsafe, IMO.
>>     However, safety did not seem to be a big concern "back in the day"...
>>
>>     On Saturday, August 28, 2021, 12:29:46 AM EDT, Hubert Miller
>>     <kargo_cult at msn.com> <mailto:kargo_cult at msn.com> wrote:
>>
>>
>>     Here's a 348 i found in my stash. The rectifier tube is a 25Z5,
>>     which means a drop -in supply with minimum mods. Unfortunately
>>     tho, the cabinet top has been aerated. The PS has no markings
>>     really except for this on the tube area shield:
>>     "TESTED GOOD 11/10/ 45 ROB". Too early to have hit the surplus
>>     stores, so this must be a gov't mod.
>>     -Hue Miller
>>     -- 
>