The Mississippi Historical Radio and Broadcasting Society
| Vol 3 #7 | February 26, 1994 |
News Letter
It's Show Time!!!
The Mississippi Historical Radio and Broadcasting Society's Spring 1994 Show and Meet
When: March 12, 1994 9AM to 6PM
Where: JayCee's Building, Hwy. 39 N
Who: Everyone is invited!
How Much: Members (and family) free; a dollar donation per family requested from the public.
What: Museum, Swap meet, Auction, Contests, Working Displays and a Good time for all!
The show is coming together well: most of the preliminary work is done -- thanks to the efforts of many people. The last few details remaining should be worked out at our next meeting, which is March 8, 1994 at 2412 C St. 7PM. This is a very important meeting, please everyone who can, try and make this meeting!
Advertising is basically in place: space / time is already running in/on: The Meridian Star, WTOK TV, WGBC TV, ETV, PRM, WZMP, WMGP, WJDQ, The Memphis Commercial Appeal (including article on Sunday); and several other papers and stations have indicated they will start running spots shortly. WGBC (NBC channel 30) has invited us to appear on their noon television show to promote the event on Monday March 7 -- any volunteers???? To all of them we are thankful. Another good bit of news is that we have picked up a corporate sponsor. The law offices of Minniece, Hamill, Wilson, Mitts & Neville have made a sizable contribution to the club for which we are grateful.
At this moment, we don't know if Randy Corbin is going to be able to attend the show or not (his fire fighting class is scheduled for certification in Jackson March 12), so-- any volunteers to pick up the slack??? He usually provides a ton of "services" like outdoor signs, antennas, a strong back to move equipment, and most important -- he is the club's pop-corn master chef. Larry Clark & company have already volunteered to step in and take on Randy's HAM exhibit duties this year, including setting up a station and running demonstrations of "Packet" and other current HAM activities. Farrar and Charlie Grisham have been "volunteered" to assist Larry in that endeavor...
Bill Gerk and Bob Jordan both suggested that everybody bring a couple of 2-Liter Cokes to the show like we did last year. Doing so really helped raise funds for the club.
The remaining things to be covered at the next meeting:
1) museum displays - who is planning to bring what???
2) Personnel assignments during the show - such things as door / registration desk, snack bar, security, parking lot, etc. Who is going to available when and for what??
We are including a couple of show flyers and a map with this mailing - distribute these where you can. We've already had inquiries from as far as Florida!
So-- important dates to mark on your calendar:
Mar. 8:Regular Monthly Meeting
Mar. 12:Annual Meet & Show
Apr. 12:Regular Monthly Meeting
May 10:Regular Monthly Meeting
Radio Collecting Today
{Editor's Note - This is the little Zenith Cube that is seen in several places around the Museum Site - and in the North Wing}
The Quandary: You get a great little radio. But it isn't what it was!?! - or is what it wasn't?!? Here is the dilemma: You get a nice little Zenith cube - AM & short wave. Glancing over it briefly, you judge it's age at about 1937 or so. The chassis is complete, nothing appears out of the ordinary, the power transformer looks ok - no filter caps in sight - but that is common in Zenith's - they often used axials under the chassis. The tubes are all there and a common complement - 6A8 converter, 6K7 IF, 6Q7 Det, & 1st AF, 41 output, 80 Rectifier. My father-in-law has had this radio for more years than I dare relate & I have admired it (ok, lusted after it) for a long time. Last Christmas, he and my mother-in-law made it a birthday present to me -- I was delighted. After the holidays were over, and in anticipation of the spring show, I decided to restore the set. I pulled out the Zenith book and looked the set up. Here is the picture: Went to the index and looked up model 5F233: on page 410. Ok, to page 410 - Hmmm...HUH!!!!! 1C7 converter, 1D5 IF, 1F7 detector & 1st AF, 1H4 Driver, and a 1J6 output???? Hmm... must have gotten the wrong page number (dummy me!) back to the index, CAREFULLY(!) lookup 5F233: page 410. Back to 410 --- this time look at the model numbers and chassis designations-- 5F233 and 5F231 (5522 Chassis). Hmmmm.... Battery set. Closely look at the chassis: power transformer, 80, 41 output -- Hmm... ponder, ponder... yep; been converted. Who ever did it did a good job - no butchering here. Apparently Zenith used the same metal chassis for a couple of sets besides these two - and made it so that it could be battery or AC. Therein the dilemma: do I restore it back to original (battery), or do I restore it as converted. Purist (those who try to restore a radio to the way it was originally from the factory would have no trouble with this question - they would take it back to battery. But since I describe myself as a "practical" restorer... the question isn't so simple. I do try to restore radios to as original as possible - but using modern components. But this isn't just a matter of "original" parts vs. "working" parts. Here the basic design of the radio has been changed - and many parts replaced, rewired, etc. First: what is meant by "electrifying?" This means converting a radio to run on AC power directly - as opposed to just making a power converter for the set - to deliver battery voltages from the AC mains. When "electrifying" a battery set, there are several important considerations:
1) battery tubes are (usually) direct heated cathodes and will not work correctly on AC: the filament supply must either be converted to DC - or AC tubes substituted.
2) battery sets often use a "C" battery to develop negative bias for the audio stages. AC sets develop that bias voltage through some sort of network - usually by inserting a resistor in the ground side of the power supply, or in the cathode lead of the output tube(s) - a little bit of re-wiring.
3) Battery sets virtually always have one side of the battery tied to ground - so if you bring AC directly in, you have a "hot" chassis - a transformer is a must.
4) battery sets have very few "power supply" parts by their very nature - obviously many additional parts are needed.
I decide that if the conversion done on this radio was done properly, I'll keep it as an AC set. So the first step is to create a complete schematic. That is not as hard as it sounds. First: Make a working copy of the original. Use this as a master "road map" -- mark off each section, and circuit as it is (or is needed) in the new configuration. Most of the wiring and parts are going to be unchanged in the converter stage - so that is the best place to start. In going through most radios, we normally start with the power supply - but since this is going to contain the most changes, we'll get to it last. On a blank piece of paper, using the original as a guide, draw the input stage (antenna coils, tuning, etc.) for the converter stage. Then using your tube manual, draw in the tube that is actually in the radio. Then referring to the radio itself, draw in the connections. Continue with the remaining stages until you get done. The audio stages and power supply will require the most work - as they will be the most changed. If the job has been done right, you will find that the schematic you draw looks remarkably the same as the original, with just the pin numbers changing on the tubes -- and the addition of the AC parts of the power supply. This is the case with this radio - whoever did the conversion did an excellent job. The new bias network and power supply are all well designed and competent.
This being the case, my decision is now easy: recap the set like any other set - using my newly drawn schematic for a reference - Refinish the cabinet and I'll have a dandy little Zenith cube. Hope to have it on display at the show.
Next time: looking deeper into the purist vs. "practical" question: how far is far enough and how far is too far - and who is to decide?
In the meantime: Happy Collecting!
The Mississippi Historical Radio and Broadcasting Society Newsletter is published monthly by:
The Mississippi Historical Radio and Broadcasting Society
2412 C Street
Meridian, MS 39301
601 693-5958
© 1994, The Mississippi Historical Radio and Broadcasting Society.
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