The PHILCO Phorum

707. Way back in the mid '60s I had an Emerson 737 (same set as 706/707 just a plain frt and no indicator lamp). It was a gift from my grandmother. Used to listen to into the wee hours in the night. Somewhere along the way it got gone. It may have been the set that the speaker caught on fire like the beginning of Bonanza. I don't remember. Have always like the little guys and would pick them up when the price was right. Have three now.

Thought it might be fun to soup it up a little by adding some gain in the front end. It's a pretty standard ac/dc set but built on a small chassis. Uses a 12BE6 for the mixer as most do. There is a tube that has abt 3X the gain which is a 12BA7. It was original designed for mixer service in FM sets but didn't get used much. It's not a drop in replacement for the 'BE6 as it has a 9 pin base.

Fortunately the tube socket hole in the Emerson chassis are large and will just accommodate the 9 pin socket but had to enlarge the screw holes to mount it in place. Made all the connections to the socket and gave it a try. Haven't realigned it yet but it works swell !!

There is a 6v 300ma octal version of the 'BA7 which is a 6SB7. It is a drop in for the 6SA7. Unfortunately there isn't a 12v octal (12SB7 )

Very interesting. Let us know how the alignment goes, and how the set performs when it's all done.

Take a look at this fellows site:

http://www.wa2ise.com/radios/12ba7.html


http://www.wa2ise.com/radios/12ba7.html

The Emerson has an intermittent problem w/static crashes that are controllable w/ the volume control. It's not from 12BA7 mod, it had the problem before. Thinking a bad if can. When it was working I did take notice that on an unmodified set fading stations like the CA stations would fade down nothing where the modified set would fade some but still very copyable. I don't have a good calibrated generator w/good attenuator in microvolts. So the results arn't scientific just anecdotal.

Chas, I saw that site a while back and it was one of the things that encouraged me to give it a whirl. I'm pretty sure I remember reading about back in the '60s. Back in '52 Collins updated their 75A2 from using the 6BE6 to the 6BA7 has two. Something else awaiting repair...

(12-27-2018, 10:27 PM)Radioroslyn Wrote: [ -> ] like the beginning of Bonanza.

Have a Panasonic RE-784A  AM/FM AC/DC set. The tube line up 17EW8, 12BA6, 12BA6, 12AV6, 50C5, an 12BE6. Sorry I do not have a good copy of the sch. There is one on the bottom of the set not real clear. Purchased at a yard sell 20 plus years ago. All I did was replace the 4 Ecaps and a couple of paper cap all resistors were good most of the caps were ceramic disc. Have not played the set in like 5 years so gave it a try and good to go. Found some info at wikipedia of all places.   https://en.wikipedia.org/wiki/National_P...el_RE-784A  The other radio site has info but I am not a member.

Typical Wikipedia, National Panasonic is NOT defunct, National Radio was the trade name for Matshushita Industries, which is still very much in business. They changed their name to National Panasonic after they started exporting sets to North America to avoid confusion with the existing National Company of Malden, Massachusetts, of the time. I know of someone who has that same AM/FM radio, I found them a power cord for it since the original was missing, it was still working but needs an overhaul like any other 50+ year old tube radio.
Regards
Arran

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When i fixed the radio was before the internet for me at the house. looked up the 17EW8 it is just a 12DT8 with a higher heater voltage. Checking a couple sites cost less than the 12DT8 so will pickup a few for the Z set and others using the 12DT8.