[Radioroslyn]

Bakelite vs brass. Any reason why or time frame for when they were used? I was gifted one, a complete 90 the second one I've had since the late '70s. That one is long gone.

Tnx

[Ron Ramirez]

Brass - all early models (with two 45 outputs), early production of “mid” models (one 47 output).
Bakelite - later production of “mid” models and all “late” (2-47) models.

[Brad Winder]

I believe I remember a "chart" or graph in the ARC magazine several years (decades now !!) ago where a group had charted and tracked known manufacture dates of the 90's, along with the changes in the output tubes used and the move from brass to bakelite escutcheons. It was all very interesting!

[Ron Ramirez]

Yes.

That work was credited to Ron Boucher and myself, although Ron Boucher deserves 99% of the credit - I helped out a little by gathering serial numbers from people and sending to him.

[Brad Winder]

I *might* have a copy of that...

There was so much information in that magazine, and it's a shame the younger members don't have any access to that, aside from searching out old copies.

IF information like that was to be scanned, could it be posted to the Phorum? Or would we run into copyright issues?

[klondike98]

It’s probably new enough that copyright could still be an issue but if publishers are still around we might be able to get permission to reproduce

[Ron Ramirez]

Most likely, the person to ask about that would be Jon Kummer, since he bought the magazine from John Terrey.

His contact info may be found at the bottom of Antique Radio Classified's website, which is still up and upon which Jon still sells books.

I should clarify that I only assume Jon is still around. I know he was at the last Kutztown party I was able to attend (May 2018). Yeah, five years have passed...

[Ron Ramirez]

The pertinent issues (there were three parts) are July 1994, May 1995, and July 1995.

These are available on the wonderful World Radio History website.

July 1994

May 1995

July 1995

[Radioroslyn]

Thanks Ron for the info! I picked up one by default at Ktown yesterday that was in the auction. I was talking w/Mike (walrus) who has a 90 and he was saying that he has never seen one with a bakelite bezel. I was a little surprised I seen both but didn't know if there was any rhyme or reason for the implementation of one vs the other. And Now I know.

I have a request for someone w/magical powers. Over in the Library could I.F. frequency for the different 90's chassis be written in on the schematic and service bulletins? It's not listed in the service literature per say and is list somewhere in the Library. It took me a little digging around to find it. Having it on the schematic would very handy for all who are servicing these sets.

[Ron Ramirez]

Good point, Terry. This is especially important since the service information over the decades regarding the "mid" version 90 has a glaring error - in much of the literature, the "mid" 90 is listed with an IF of 260 kc. This is incorrect. The "mid" 90, like the early 90, has an IF of 175 kc. Only the "late" 90 (with two 47 output tubes) has a 260 kc IF.

I just finished a "mid" 90 (I've been writing about it on my blog) and it received proper alignment at 175 kc. It is, by far, the best and most sensitive 90 I have ever owned. (Oh, darn, I just gave away the ending!)

[Nathan Slingerland]

Thanks Terry and Ron!

I've updated the Early Philco Schematics for the 90 models with the IF frequency information:
https://philcoradio.com/library/index.ph...chematics/

(Editing the service bulletins PDFs will take some additional effort - will take a look at that soon.)

[Radioroslyn]

Originally I thought that all of the 90's had avc but after looking at the schematics I was wrong. The 1st gen is an early 70 w/ p/p 45 output. I would imagine it's loud and a bit beastly to tune in. The one that I ended up with is the one with the single 47 in the output stage.

[Ron Ramirez]

The 90 with a single 47 (second version, middle version or mid version) appears to be the most common of the three versions.

Correct, the early 90s with two 45 outputs do not have AVC. They operate in the same manner as an early model 70 as you said, only with two additional tubes in the audio section. The circuitry of the early 90 up through the 2nd detector is basically the same as the early 70. And, both use the plate detector circuit so they both suffer from the same distorted audio.

The "mid" 90 was improved by eliminating the 24 used as a plate detector, and using a 27 instead as a second detector, connected as a diode. They also added another intermediate stage of audio amplification. To keep the tube count at nine, the push-pull 45 output circuitry was changed to a single 47.

An early 90 isn't hard to tune, neither is an early 70 (or any radio without AVC for that matter). You just have to have one hand on the volume control knob if you live in an area with very strong local signals.

[Radioroslyn]

Didn't mean that it was hard to tune but you mention the blasting effect. It's beastly like the 70. Living near Philly there are a lot of strong stations and at night avc make tuning around much more pleasant.

I do have another question about the chassis. It's missing the rf tube shield. There is a clip mounted towards the front of the chassis that holds it. What holds it at the back if anything?

[Ron Ramirez]

A single screw holds the shield in place at the back of the chassis.