[AMRadio] R-390A Help


rbethman rbethman at comcast.net
Tue Jul 8 13:28:57 EDT 2014


I'd add that there is NO reason to buy a 3TF7 ballast tube.

A simple and inexpensive 49 - 50 ohm 10W resistor across the two pins 
the 3TF7 uses is all it takes!

Ran a '67 EAC that way for about 6 years.  Not a single problem. I do 
happen to have a 3TF7, but I'm going to just hang on to it. I also have 
a handful of the 26Z5Ws.  I worry less about solid stating them than I 
would worry about that selenium rectifier.

When the selenium rectifier goes, you definitely do NOT want to get a 
nose full!  It is a nasty gas that they let go of!  Not good for the 
human body.

The two can caps can be gotten from Tom N0JMY at hayseed hamfest. They 
make them from the ground up all new.

Re-stuffing them is a pain that only gives you the "satisfaction" of 
making it "appear" to be original.  Not worth the work and effort.

Make sure all the capacitors are up to snuff!  Usually better to re-cap 
if it isn't an EAC.

Almost all the rest are too old and have the Brown Beauties, referred to 
as BBOD, (Brown Beauties of Death).

Make darn sure that the DC blocking cap on the filters is rated for 1 or 
more KV.  You don't want to be blowing filters!

Filters are getting as rare as hen's teeth!

Bob - N0DGN



On 7/8/2014 12:43 PM, W2xj wrote:
> You should really download an on line version as some have more detail and background information.
>
> I should note that every single tube in that radio can still be bought as old stock never used online.
>
> These guys have everything but the ballast tube which can be had from fair radio
>
> http://www.vacuumtubes.net/prices.htm
>
> Rectifiers are $20 each and the ballast is $60 while the other tubes are between $3&$7. That is a good reason to go solid state on those three expensive tubes.
>
> Sent from my iPhone
>
>> On Jul 8, 2014, at 11:51 AM, Bill Guyger via AMRadio <amradio at mailman.qth.net> wrote:
>>
>> Thanks to all that replied, now to go diggin'! Just wanted to see if any of you had any hot sports opinions before I go hunting.  Shouldn't be a real chore once I get time, a manual was included along with the radio.
>>
>> Tnx 73 Bill AD5OL



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