[Boatanchors] Revisiting: the R390A & 3TF7 substitutes

[Raymond Cote]

Thanks for the reminder /

Raymond Cote
Ex US Navy
ET1 (SS)
Submarine service
 
Ex Univ of Hawaii
Oceanography
underwater volcanology
Seismology

HAM RADIO license. KD9CCZ
Commercial radio telephone license PG-21-3809
Since 10-30-1987

> On Aug 7, 2015, at 21:31, Al Klase <ark at ar88.net> wrote:
> 
> Hi Doug,
> 
> Schematic here: http://www.radiomuseum.org/tubes/tube_3tf7.html Looks like that's pretty much what the guy on E-bay is doing. Bridge rectifier and a three-terminal voltage regulator into a load resistor. 30 bucks ain't so bad for something that's ready to plug in.
> 
> Mish's solution is perfectly valid for most of us, unless you have wildly varying line voltage. I think the original spec was 90-130 VAC.
> 
> Another way is to short across the 3FT7 socket, and replace the two 5749's (6BA6's) it regulates with 12BA6's.
> 
> My two cents,
> Al
> 
> Al Klase – N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
> 
>> On 8/7/2015 8:10 PM, Doug Hensley wrote:
>> Poking around for information on a solid state replacement schematic, I found some interesting comments on a fix.  People are reporting that Rick Mish puts a 40 ohm 10 watt Dale resistor where pins 2 & 7 had been and removes the socket.  A seller or two on the e-Place are marketing G-10 9 pin plugs with a current regulator and pair of resistors mounted on a small vertical board.  It, I guess, is a more professional solution but I have not found a circuit for it yet or parts list.
>> I really don't want to go chasing after 3TF7 tubes so polling the list here for what seems to work best for them.
>> Thanks,
>> Doug
>> 
>> 
>>  
>>                         
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