[Mondial]

This is just a thought, but I wonder if in the past a previous owner replaced the dial scale. The code 125 chassis used a different dial than previous runs which had a different frequency calibration. Does the dial look original or was it possibly replaced?

When you did the alignment is trimmer #40 at max capacity (tight)? Are antenna 22A and mixer grid 22B trimmers also fully tight? It seems unusual that the radio receives well if the oscillator is off since it must track with the antenna and mixer tuned circuits.

[morzh]

Mondial

I thought the two dials (plain and robodial versions) are so different they could not even be mount one instead of the other.

[Ron Ramirez]

Mondial is, I believe, referring to the 37-690 dial vs. 38-690 dial.

Also, Philco did not make the 37- or 38-690 with standard tuning - only with the Automatic Tuning dial.

[RGK20m3]

Well, I think you are on to something.  The dial that I removed was broken along the edge in 2 places, and the center was broken out (it had a 300 degree circular gap around the hub; the remaining 60 degrees was where it attached- I assumed to allow it to align with the guides). This dial has part number 27-5340
The replacement came in an envelope (which I retained) and was marked DS-A571 (or DS-H571); when I go to their website, it says that part is for a 38-116
Before I installed the replacement dial, I compared the graphics and they are the same. But now that you mentioned it, I checked and both old and new scales are compressed at the upper end (a little over an inch from 1500 to 1600, but an inch from 530 to 580).
Even though both the 38-116 and the 38-690 have magnetic tuning, are the dials calibrated differently? I did have to file a notch for the hub to locate on the replacement dial.....they both use the same tuning condenser on code 125.

[morzh]

Ron

Yes, I thought of 37-116, of course.

Speaking of dials possibly rotated (shofted) it is still strange as even if I were too draw a dial by hand on a piece of paper, if I aligned it with a calibrated RF generator, no matter what dial it is, it will receive a proper station at a proper place on the scale.

If the scale is different in the way that it's longer or the dependency of frequency vs space is not linear, butr say log or whatever (depends on tuning cap geometry) then of course, it won't conform, but at least that one point you aligned the radio at will always be correct. Not shifted.

[Mondial]

Yes Ron, that's what I was referring to. The earlier models with the regular tuning cap vs the later with the split stator cap. The dial calibration is different.

I kind of remember this because I have a late production 38-116 code 125 which has the newer split stator front end and saw the schematic of earlier 121 chassis has the 37 style tuner.

I wonder if the dial scale is lined up correctly. The 38-116 has an alignment procedure where the tuning cap is first fully meshed and set to the index. The cap is tuned back to 4.71 MHz and the dial is then reset again to the index. Since the 116 and 690 both use the same tuning cap and dial, maybe this procedure would be the same and increase the dial accuracy?

Check the dial alignment procedure for the 38-116 code 125, as it is not just setting simply to the index line.

[Ron Ramirez]

Model 38-116 Code 125 and model 38-690 use the same RF unit and the same dial scale - 27-5340.

Model 38-116 Code 121 uses the same dial and RF unit as models 37-116 Code 122, 37-675 Code 122, and 37-690. The dial scale on these is 27-5207.

While both cover the same frequency range, the two have different calibrations.

DS-A571 is Radio Daze' part number, with no relation to an original Philco part number.

[RGK20m3]

Didn’t know if using a vendor name was allowed; their website does not mention whether that part fits the 38-690 (probably because it requires minor modification). I did know that was a vendor part number.  The 38-116 alignment instructions include a dial alignment, where the 38-690 instructions do not, so I will try that along with another alignment.  Yes, 40, 22A, and 22B are very near the end of adjustment tight, along with 39A (the hex).

[Ron Ramirez]

It should not require modification - again, the RF unit of the 38-116 Code 125 and 38-690 are identical.

Yes, the available service info for model 38-690 is lacking in some ways.

[RGK20m3]

The reproduction dial was definitely different, lacking the 300 degree slot around the hub, lacking the key slot, and having two small holes 180 degrees apart (for alignment pins I assume). Only modification for it to fit was to file a notch for the key on the hub; the other differences didn’t affect fitting. It was easy to file the notch as I had the original dial to compare.

[RGK20m3]

Success!  I performed the dial alignment per the 38-116 instructions, then carefully performed a realignment and the dial is now exactly on stations at both the high and low ends of the broadcast band. I also registered higher peaks on the other 4 bands.
It must be that the initial inaccuracy at the low part of the band could be trimmed, but at the higher end there was not enough range in the compensators to tune (probably because of the logarithmic scale).  Didn’t take a huge movement of the dial to the condenser to correct it.
Thanks to all for the input and suggestions, very much appreciated!

[Mondial]

Glad you got it worked out. Makes sense, since the 39A compensator at the low end has a lot more adjustment range than 40, the high end compensator. The dial calibration lines are more compressed at the high frequency end, so just a slight rotation of the dial makes a bigger correction than at the spread out low end. Really what they did was set the high end dial calibration by shifting the dial and then corrected the low end with the 39A padder compensator.

That resetting of the index in the 38-116 procedure is a bit of a fudge. Never saw a procedure like that before. Guess someone at Philco originally made a mistake in laying out the dial and then production just offset the index alignment to compensate.

I assume that now, neither index lines up when the tuning cap is tuned to the end stops?

How does the color of your repro dial compare with the original? I bought the same repro dial from Radio Daze a few years ago but was disappointed in the color and translucency. It was made of a rather dark phenolic material, a lot different from the amber colored original. I wonder if they are using better material now?

[RGK20m3]

The alignment marks still line up; there is a greater range of rotation built into the condenser than the dial mechanism has.  That was what threw me off, I thought the condenser stops are what limited rotation; and when both dial ends lined up, I figured the condenser was aligned.
I bought the repro dial from Radio Daze probably 5 years ago, when I first acquired the 38-690.  It is of a much darker material than the original, and doesn’t illuminate well (especially the magnetic tuning flood lights; you can barely see the preset station tabs).  Been thinking about either A) paint the bulb reflectors white or silver, or B) get some greater lumen warm white LEDs.
I still have the original dial, which I could glue back together if I can find another for some small missing pieces along the outer edge.
Now to construct a better aerial.....

[RGK20m3]

New issue- magnetic tuning doesn’t seem to work at all. Going through the adjustment procedure 85B(hex), 85A, and 77 seem to have zero affect. I have already checked the on/off switch and the speed tuning switches and they work correctly. Replaced paper caps and checked all resistor values (except 20k, as that has the coil in parallel). I tried adjusting trimmer 85A every 1/4 turn of 85B throughout it’s range....any suggestions on how to diagnose this?

[Greg]

The automatic tuning of my 37-116 didn't seem to work when I restored it. The problem was that there are two switches for it. The switch you see on the cabinet that turns it OFF. And...

There's a switch that part of the preset mechanism that turns it off, I believe, when you engage the arm that's used to tune to a preset station. Somehow that was engaged until I exercised the preset tuning. I keep telling myself I'll go back and figure exactly how it works mechanically. Haven't gotten there yet.

I think it needs to be off when tuning since it appears that it can drag a station pretty far before "letting go".