[Milsurplus] [ARC5] A.C. Modified BC-348

[William Cromwell]

Hi,

I have a Mont'gy Wards receiever built in the 40s that uses all 
'series-string' tubes with three different voltages for the heaters. I 
was able to get a copy of the manual for it. The power transformer has 
separate windings for each of those voltages. At my first look inside 
the radio (without the manual) I assumed a series string. Then why the 
transformer with all those windings?

A ham friend builds radios with tubes and favors those "odd" voltage 
tubes for his projects because they are so *cheap*. He uses the heaters 
in series but from 12 and 24 volt transformers. Maybe he even gets paid 
to take them (evil grin). I sent him all of mine. They are on the air now.

We don't have to rum them 'as marketed'.

73,

Bill KU8H

bark less - wag more

On 8/28/21 11:12 AM, Mike Feher wrote:
>
> I have not seen a schematic of this PS. While the 25Z5 was designed 
> and typically used in series string designs, they do not need to be. 
> They are just a rectifier tube and as such can be used in any way the 
> designers decide. 73 – Mike
>
> Mike B. Feher, N4FS
>
> 89 Arnold Blvd.
>
> Howell NJ 07731
>
> 848-245-9115
>
> *From:* arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> 
> *On Behalf Of *J Mcvey via ARC5
> *Sent:* Saturday, August 28, 2021 10:42 AM
> *To:* arc5 at mailman.qth.net; milsurplus at mailman.qth.net; Hubert Miller 
> <kargo_cult at msn.com>
> *Subject:* Re: [ARC5] A.C. Modified BC-348
>
> 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
>
> Sent from my Verizon, Samsung Galaxy smartphone
>
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