[Boatanchors] Re: [Heathkit] Question on 12AU7

[wolfbob]

The inrush current conditions would be different but the 
steady state all warmed up condition would have a current 
slightly higher than the lowest and less than the highest of 
the series string. Just what it would be would depend upon 
the transformer impedance and voltage. I dont think you 
would notice the shortened heater life of the one running 
higher current nor would you notice the shorter cathode 
current life of the one running slightly cooler although 
both effects would be in play.

WBob, WB6JPI


----- Original Message ----- 
From: "jeremy-ca" <km1h at jeremy.mv.com>
To: "Revcom" <revcom at wbsnet.org>; "Dan Pividal" 
<dpividal at tampabay.rr.com>; "boatanchors" 
<boatanchors at mailman.qth.net>; <heathkit at mailman.qth.net>
Sent: Saturday, February 02, 2008 9:55 AM
Subject: Re: [Heathkit] Question on 12AU7


> Just about all you ever need to know about those tubes and 
> many others is on the site I posted on here yesterday.
> If you notice; not all manufacturers report identical 
> specifications.
>
> http://www.tubedata.org/
>
> Carl
> KM1H
>
> ----- Original Message ----- 
> From: "Revcom" <revcom at wbsnet.org>
> To: "Dan Pividal" <dpividal at tampabay.rr.com>; 
> "boatanchors" <boatanchors at mailman.qth.net>; 
> <heathkit at mailman.qth.net>
> Sent: Saturday, February 02, 2008 11:57 AM
> Subject: Re: [Heathkit] Question on 12AU7
>
>
>> Dan,
>> I am by no means an expert on this, nor an engineer, so 
>> others may
>> add to the comments that know a lot more.
>>
>> When was doing a lot of tube type service work, we had 
>> both 12AU7s
>> and 5814s.  Boss said to use the 5814 for long life use, 
>> on 24hr a day
>> operation.  Mostly used in audio and switching, like 
>> flip-flops, and servo
>> amps.  Not RF applications.
>>
>> According to my old GE -Essential Characterstics- book, 
>> c1963, the
>> 5814 is listed as a "special 12AU7".  It was also listed 
>> as a 5 star product
>> from GE, graded for mil-spec applications and the like I 
>> guess.
>>
>> Now the 5814 draws a little more on the filament, 0.175A 
>> at 12.6V while
>> the 12AU7 is rated at 0.15A at 12.6V.  That would mean 
>> you would not
>> want to mix them in especially series applications, i.e. 
>> 24V mil gear. and
>> if you had a lot of them it might burden the filament 
>> supply too much.
>>
>> We used a lot of them in audio chains, old microwave mux 
>> gear and some
>> mobile applications.
>>
>> 5814 rated at 2.7 max plate watts, while 12AU7 at 2.75, 
>> some diff there
>> too.  But major difference is the output capacitance of 
>> 0.5uufd for the
>> 5814 vs 2.0uufd for 12AU7.
>>
>> So generally, they are a "direct" sub, but not really.
>>
>> Rod
>>
>> ----- Original Message -----
>> From: "Dan Pividal" <dpividal at tampabay.rr.com>
>> To: "Revcom" <revcom at wbsnet.org>
>> Sent: Friday, February 01, 2008 6:04 PM
>> Subject: Re: [Heathkit] Question on 12AU7
>>
>>
>>> What type circuits should I avoid Rod?
>>> Dan/N4VET
>>> ----- Original Message -----
>>> From: "Revcom" <revcom at wbsnet.org>
>>> To: "Dan Pividal" <dpividal at tampabay.rr.com>; 
>>> "heathkit at mailman.qth.nt"
>>> <heathkit at mailman.qth.net>
>>> Sent: Friday, February 01, 2008 6:38 PM
>>> Subject: Re: [Heathkit] Question on 12AU7
>>>
>>>
>>> > In most all circuits they will work just fine. 
>>> > Probably last longer.
>>> > Rod
>>> >
>>> > ----- Original Message -----
>>> > From: "Dan Pividal" <dpividal at tampabay.rr.com>
>>> > To: "heathkit at mailman.qth.nt" 
>>> > <heathkit at mailman.qth.net>
>>> > Sent: Friday, February 01, 2008 10:50 AM
>>> > Subject: [Heathkit] Question on 12AU7
>>> >
>>> >
>>> >> Is the 5814A a direct substitute for a 12AU7A?
>>> >> I show it is when I go to some tube sub charts.
>>> >> I have a bunch of 5814A and would like to know.
>>> >> Dan/N4VET
>>> >>
>>>
>>>
>>
>>
>
>