[ARC5] Fw: Receiver current drain

[Henry Mei'l's]

John,

Yes I see your point. As previously mentioned, I'm quite satisfied with the 
audio output level.
That also goes for my BC-342, WS 19-MkII, BC-603 and my no longer owned TCS
RBM and RCH, recievers.

Henry

----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "Henry Mei'l's" <meils at get2net.dk>
Cc: <arc5 at mailman.qth.net>
Sent: Thursday, January 06, 2011 8:22 PM
Subject: Re: [ARC5] Fw: Receiver current drain


> Henry,
>
> I have not analyzed the circuit and don't have the specs on the
> transformer, without which it'd be pretty hard to figure it out. You can,
> of course, figure the transformer's dissipation from the primary
> resistance and plate current.
>
> Frankly, contrary to much "ham lore", I firmly believe the original
> designers of these (and virtually all other) military radios knew
> precisely what they were doing. They were at war, and lives depended on
> the stuff working.
>
> YMMV,
>
> -John
>
> =============
>
>> Thanks for the warning John. Thought there had to be a minus side.
>> Would a more moderate resistance decrease be a workable solution?
>> I haven't taken note of how much reduction was originally suggested.
>> Suppose the original value was chosen for optimum performance/linearity
>> and longevity of the 12A6.
>>
>> Best wishes,
>> Henry
>>
>> PS- My emails to you bounce when I use this address but get through via 
>> my
>> yahoo address
>>        -guess you'll see this via Cc: ARC-5
>>
>>
>> ----- Original Message -----
>> From: "J. Forster" <jfor at quik.com>
>> To: "Henry Mei'l's" <meils at get2net.dk>
>> Cc: <arc5 at mailman.qth.net>
>> Sent: Thursday, January 06, 2011 7:57 PM
>> Subject: Re: [ARC5] Fw: Receiver current drain
>>
>>
>>> Henry,
>>>  I'm not so sure lowering the cathode resistor is such a good idea.
>>>
>>> The suggested change will roughly double the 12A6 plate current, and
>>> hence
>>> increase the dissipation in the output transformer primary by 4X.
>>>
>>> It also might saturate the transformer with excessive DC, since the
>>> radio
>>> has a single ended output stage.
>>>
>>> Best,
>>>
>>> -John
>>>
>>> ==================>
>>>> ----- Original Message -----
>>>> From: "Henry Mei'l's" <meils at get2net.dk>
>>>> To: "Mike Morrow" <kk5f at arrl.net>
>>>> Sent: Thursday, January 06, 2011 7:32 PM
>>>> Subject: Re: [ARC5] Receiver current drain
>>>>
>>>>
>>>>>I also find that current drain varies from about 10-15 mA to 25-28 mA
>>>>>depending on the B+ level.
>>>>> Have also always found output sufficient for loudspeaker operation.
>>>>> Nice
>>>>> to know I can get more
>>>>> output by changing the 12A6 cathode resisistance, if I should ever
>>>>> need
>>>>> increased audio.
>>>>>
>>>>> Henry. oz1uf - n2nr
>>>>>
>>>>>
>>>>> ----- Original Message -----
>>>>> From: "Mike Morrow" <kk5f at earthlink.net>
>>>>> To: <ARC5 at mailman.qth.net>
>>>>> Sent: Thursday, January 06, 2011 6:52 PM
>>>>> Subject: Re: [ARC5] Receiver current drain
>>>>>
>>>>>
>>>>>> >We must remember that in military service, this tube was driving
>>>>>> >headphones
>>>>>>>at the 100-200 mW level so there was no requirement to generate a
>>>>>>> large
>>>>>>>amount
>>>>>>>of audio.
>>>>>>
>>>>>> Is that really true?  WWII-era aircraft interphone systems
>>>>>> (pre-AN/AIC-2)
>>>>>> did NOT
>>>>>> amplify the audio of ANY receiver connected to the system.  They
>>>>>> simply
>>>>>> routed
>>>>>> receiver AF outputs to each station box.  Bomber installations of,
>>>>>> say,
>>>>>> the
>>>>>> SCR-274-N could worst case have ten headphones connected in parallel
>>>>>> to
>>>>>> the AF
>>>>>> output of the receivers. (Though most stations would be usually
>>>>>> selected
>>>>>> to the
>>>>>> interphone amplifier's AF output, itself usually a simple one-tube
>>>>>> amplifier that
>>>>>> amplified *only* microphone audio.)
>>>>>>
>>>>>> Apparently the AF output of the command, liason, and DF receivers was
>>>>>> enough to
>>>>>> meet the demand.
>>>>>>
>>>>>>>...some owners have in the past reported adequate audio output into a
>>>>>>>loudspeaker
>>>>>>>even with the original value...
>>>>>>
>>>>>> In the 1960s, I often used a BC-453-B to monitor maritime Morse
>>>>>> around
>>>>>> 500 kHz.
>>>>>> I got adequate drive for a speaker by using an appropriate
>>>>>> impedance-matching
>>>>>> transformer.  No receiver AF tag modifications were required.  (I
>>>>>> used
>>>>>> a
>>>>>> 240 vdc
>>>>>> HV supply.)
>>>>>>
>>>>>> Mike / KK5F
>>>>>>
>>>>
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>>>
>>>
>>
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