[Michael Dennis]

Maybe I'm missing something simple, but what is the difference between code 121 and code 122 for the same model radio, in this instance the 42-1008 console radio/phono?

[Carl Travis]

Have you read this explanation of codes on Chuck's site?
http://www.philcorepairbench.com/tips/svctip35.htm

[Michael Dennis]

Thanks, Carl, I must've missed that. Edit: After reading the info I'm still stumped. I have an old chassis for the 42-1008 and the circuitry uses a 5Y4G rectifier, it's stamped code 122. This complete radio I recently accquired, less the turntable, is stamped code 121 on the chassis rear, and is also on the paper lable inside the cabinet. I haven't pulled the chassis and it's kind of hard to see the tube line-up on the paper lable, but, if I'm not mistaken the lable denotes a 5Y4G. I think I'm about due for a change in my spectacles. As I say it's kind of hard to see and the way I have it temporarily stored makes it very hard to tell as I can't move the radio enough to be able to see it. And if I'm not mistaken, when I looked at the recently accquired tech info and schematic for the model with code 121, it mentioned a 6X5 rectifier. I guess I'll have to probe a little more carefully, but thanks, guys, for your effort. UPDATE Tue. July 15: I still have the radio temporarily stored so I can't get at the chassis to pull the tubes. The only place a 6X5 rectifier is notated is on page 131 for the specifications, all other references including the schematic specify a 5Y4G, and parts changes seem restricted to the power transformer, a couple resistors, a condenser or two and the phono oscillator xfmr., which is of no consequence insofar as the record changer is absent. I've heard horror stories about certain 6X5 rectifier situations and my currently defunct RME 45 uses one of those. Shut up, Mikey, you're rambling.

Mike

[phly guy]

Mike,

You raise an interesting question (for me at least). I have a 48-460 which shows on the data tag "Code 122". While I've found plenty of data for the "code 121" version I've yet to be able to determine the difference between that and the code 122 which I have.

John

[Chuck Schwark]

The differences are in the Service Bulletin supplements. Sometimes there are just component changes. Sometimes a wiring change to accommodate a tube type change, usually the rectifier or audio output tube, or a combo, etc.

I provide these Code variations, when applicable, as part of the photocopy service packets explained on my site. Most current on-line sources for Philco schematic info do not include all this info Philco published.

I cannot remember what the details are for your model at the moment (at work).

[Michael Dennis]

Something else I wonder about, if a particular model is produced and available, say from June 1940 to March or April 1941 for the '41 model year, how far into the model year do the revisions inherent in the change from say code 121 to 122 occur? I imagine it's partially dependent on any particular model. Also, what generates the changes? Just a matter of curiosity.

Mike

[Chuck Schwark]

Production Change Notes usually extended a couple years from the introduction of a model. Some models had extensive changes. The Model 60, for instance, has numerrous changes spanning a few years. Many models had none.

Improved engineering designs, avalability of components or new style components, value changes for improved reception/stability, new/better tube changes, etc. caused changes for the most part.

Ron may have more insight as well . . . . .

[Ron Ramirez]

Well, Chuck has already explained it very well; not only here, but on his site also. Here's the link:

http://www.philcorepairbench.com/tips/svctip35.htm

For now, I can add that there was sometimes no rhyme or reason to a change in a Code number, or lack thereof.

Model 60 is a prime example.

As explained in detail on my site here:

http://www.philcoradio.com/tech/60evol.htm

For the entire run of Model 60, it remained Code 121 even though it changed a LOT during its nearly three year production run.

And then there is Model 89. Code 121 = AM only. That is clear enough. Code 123 = AM and shortwave (1.5 to 3.2 mc). What isn't so clear is that Model 89 became Code 123 when the "police" band was added (March 1933), 1-1/2 years BEFORE the Type 36 det-osc tube was changed to Type 77 (September 1934).

(edited to clarify timeline)

[Michael Dennis]

Aha, so that's what a type 77 does. I wondered because I'm supposed to be getting a couple in a bulk tube deal I won on ebay. Of course it's never a done deal until the items you won arrive intact. Paying for an item, even winning an auction is easy, but church ain't over 'till the fat lady sings. These two type 77's are Arcturas NOS and I wonder if they're blue glass envelopes. They're supposed to have never been removed from the boxes and I think Arcturas had some of the coolest tube box art.

Still no score, Fightin' Amish vs. Quaker State.

Mike

[Ron Ramirez]

Type 77 is a sharp-cutoff pentode, ideally suited for RF amplifier applications where no AVC voltage is present. The autodyne mixer-oscillator circuits Philco designed around the Type 36, and later Type 77, aren't the greatest in the world when it comes to reliability, especially long-term; Type 6A7 is MUCH better as a mixer-oscillator; it was designed specifically for this purpose.

I don't understand why Philco never improved Model 89 by changing that squirrelly autodyne circuit to one using the 6A7 when these tubes became available...but they did not. Actually, I think I do know why...Skinner was a notorious penny-pincher...and so the extra cost was probably not justified at the time.

[Michael Dennis]

Hello, Ron!

I was about to edit my above post to add that part of the bulk tube deal included (2) type 41 Philco NOS never-opened power pentode tubes, just so I could remain a member in good standing with this, the Philco Phorum.

Best Regards. Still no score, Fightin' Amish vs. Quaker State.

Mike

[Michael Dennis]

The differences are in the Service Bulletin supplements. Sometimes there are just component changes. Sometimes a wiring change to accommodate a tube type change, usually the rectifier or audio output tube, or a combo, etc.

I provide these Code variations, when applicable, as part of the photocopy service packets explained on my site. Most current on-line sources for Philco schematic info do not include all this info Philco published.

Yes, I've noticed that. Chuck, you da man and thanks for providing complete info that others don't! Seems rectifier and audio output tubes are usually the pricier ones of late. I've heard some say that the audiophiles are responsible for the dearness of the output tubes because they're willing to pay premium for them and most tube suppliers know that. Dunno, but that seems to be the conventional wisdom taken by and large. I never thought type 80's, 5Y4's, 42's, 6V6's, 6L6's and 45's especially would tend to cost so much. Having said that I have to admit some sources are seemingly significantly more reasonable than others. Sorry, Mikey's rambling again. Hey, how can I have (2) posts # 113? Is that lucky? What do I win? Ok, I know, the lovely Sterling silver tea service and a night on the town with Jack Kervorkian...

Best Regards. Still no score, Fightin' Amish vs. Quaker State.

Mike