Philco 40-180 Tracking Issue
Posts: 8
Threads: 2
Joined: Sep 2016
City: Park Ridge, IL
Hi,
First time poster. Thanks for the great site.
I just completed my first restore of a Philco 40-180 that I picked up on Craigslist. I've always liked the design of the 40-180 and 40-190. The cabinet restore turned out pretty good for my first try. I replaced all caps, any resistors that needed replaced, and any wiring that needed to be replaced. I have not replaced any tubes other than a 41 and rectifier that without question were dead (no light up) via another 41-280 dead chassis I picked up for parts and a needle that was missing from mine. The tubes I did replace were identical.
I followed Ron's procedure on the proper rocking of the adjustable caps at 1400 and 580 and followed the Philco alignment procedure. I have a B&K 2500 generator with an HP freq counter and a Fluke VM. In summary, during the alignment, IF had no issue. I tuned for 455 kHz and had about 190V off of PIN 6 of the 1232. I then went to SW 18 Mhz and peaked on the second carrier (primary) from the starting CW position slowly to CCW per the Philco procedure. I then went to 1400 kHz and rocked and had no issue. My issue comes with 580. I can't get cap 19 to tune that high. If I put the needle at 580 and the test generator at 580, I can't get 19 to peak any higher than about 565 kHz. Regardless, I followed peaked at 565 and followed Ron's rock procedure and I do believe the radio is performing very well after the overhaul. I'm picking up 620 in Canada here in Chicago, 590 in Omaha, and of course the locals are blasting in. My only issue is the dial is off from approx 550-1000. 1000-1400 is slowly curves to normal At 1400 and above, it's spot on. I didn't track SW, but I'm picking up stations.
I realize these are old radios, but given the lower end of the scale is very spread out and the upper is not, it seems silly to tune to 580 to hear WIND-560AM. Given this 1939 is about 95% of the way there, I'd like to trim this in. I don't want to simply shift the needle and find the happy medium.
Thoughts? Looking at the schematic, there doesn't appear to be anything I can cheat to help the trim cap 19. Could the OSC tube be weak? Worth a swap?
Thanks for any help you can give.
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City: Wilsonville
State, Province, Country: OR
Welcome to the Phorum!
Posts: 7,286
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Hi and welcome,
Looks like #19 is the oscillator adjustment for the low end the bcb. Let me ask you is #19 's adjustment screw, is it pretty much all the way in or out?
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 8
Threads: 2
Joined: Sep 2016
City: Park Ridge, IL
When I tighten 19 where it is almost full CW, it peaks at around 540 kHz. I can track it up to about 565 but it peaks there. From that point, I can continue to turn CCW but the nut feels pretty loose and it has no affect. 19A does exactly as you would expect on the upper end and feels pretty centered as far as the tuning range goes to 1400.
Posts: 7,286
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Don't quite understand. But no matter If the tracking getting better with the padder (#19) screwed clockwise then what you can do is add a bit more capacitance across it. Take two pieces of insulated wire abt 3" long remove a bit of the isolation from one end of each. Solder these ends the #19. Twist the insulated part of the wires together like 5 or 10 twists.The more twists the lower the stations will move down the dial. See if that improves the tracking.
GL
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 10-09-2016, 12:57 PM by Radioroslyn.)
Posts: 8
Threads: 2
Joined: Sep 2016
City: Park Ridge, IL
Sorry, Terry. To explain a little clearer, if I set my generator to 580 KHz, the highest I can shift when I adjust c19 is around 565 kHz. I can go lower, but I want the low end to come up 15-20 kHz so it matches the dial. I can turn c19 and drop it down to 540 kHz (when generating 580) but I can't get any higher than 565-568 kHz. Does that make sense?
As of right now, I've set it at 565 when generating 580 and did the rocking method to peak it there. Sensitivity is great all over the band, but is driving me crazy that the dial is off.
550-1000, about 20-25 kHz higher on the dial than actual
1000-1400, about 10 kHz higher on the dial than actual
1400-1600, perfect
IF is peaked at 455 kHz
SW is 'rocking method' peaked at 18 MHz
Posts: 7,286
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Oh that Ok anybody that know me know I'm a little thick! Well it sound like you've got too much capacitance at the low end of the dial on the BCB or there could possibly be a mechanical problem has shifted the pointer a bit.
Adding the afor mentioned gimmick cap will make it worse.
So what to do?? Well if you look at the tuning cap closely you will see several things. It has two sections, one tunes the rf signal and the other tunes the oscillator. On the two end plates of each section on the rotor you see a few cuts in the plates. These are used to set the tracking. You CAREFULLY bend out the small section that is closest the the stator( if the cap is all the way open it would be the part that moves into the stator as you turn to dial toward the lower part of the band) just a little on the section that tunes the oscillator. Just bend it out a little like an 1/8" this will reduce the total capacity of the tuning capacitor at the low end. It will also effect the SW band also.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 10-09-2016, 03:58 PM by Radioroslyn.)
Posts: 8
Threads: 2
Joined: Sep 2016
City: Park Ridge, IL
That made a difference. I felt I had to move it quite a bit to get the result. It is clearly bent now, but the dial now tracks +/- 5 Khz now which I think it good enough. WBBM 780 is actually near 780, not 805.
Thanks for the tip!
Posts: 7,286
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
No problem. It's easy when you know how! Explaining it is a bit harder than doing it.
Enjoy your new toy!
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 8
Threads: 2
Joined: Sep 2016
City: Park Ridge, IL
Terry, hoping that you might be able to help here. Because good wasn't good enough, I attempted to fine tune the IF even more after this thread. In the process, I lost all dial control, only presets. (See other post. Resolved). Now I have a working radio, with good sensitivity, but the low end won't track again. 560 is at 590. 780 at 800, 1000 at 1010, 1400 is spot on. SW band tracking is off as well. Interesting on SW, I have nothing below 9 MHz, the noise floor just disappears. Police appears to be ok. AM is fine.
When I adjust the Osc fins, I see minimal change. Cap 19 is loose. When I tighten it, It only makes 560 climb even higher than 590.
Any other ideas?
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