[FStephenMasek]

I spent some time over the past few days working to align my 38-116. The IFs needed little to no adjustment. I got the dial right on stations at 600 and 640 today, but it got to cold and late to stay in the garage working on it. This model seems to have a high degree of interaction between the 1500 trimmer and the 580 padder, as well as the antenna and RF trimmers. Any hints from those who've worked on one of these? I'm using a signal geneator, frequency counter, and VTVM.

[Ron Ramirez]

Hi Stephen

The theory found in the following thread on aligning a Model 60 should (hopefully) prove helpful:

http://philcoradio.com/phorum/showthread.php?tid=5788

Scroll down to post #12, by me.

Yes, a 38-116 is quite a different monster from a 60, but these points still hold true:

Do not rely on your ear. Connect an analog AC voltmeter, preferably, at the speaker to the two plate leads of the output transformer primary. Safety first! Do not do this with power on, else you will receive a nasty shock! Connect everything before applying power to the radio. You can use an analog multimeter, but not a digital one. It must be set to AC volts. If it has several volt range settings, start at a higher range and work your way down to a lower range until you get a strong reading on the meter without pegging the needle. The AC voltage you will be reading will actually be quite low compared to the high B+ potential.

Keep the signal you feed into the radio as low as possible, just enough to barely hear the "beep" of the signal generator with the volume control turned to maximum while being able to see good deflection on your meter. This is important!

The 580 kc padder is adjusted differently than most of the other trimmers. Here, we will utilize a process known as rocking. What you need to do now is, find the signal on the dial. Now, adjust the trimmer (12) either clockwise or counterclockwise very slightly. Turn the dial of the radio to find the signal again. Note in the meter whether the signal is higher or lower than before. If lower, turn trimmer (12) in the opposite direction and try again. If the signal is louder, continue turning (12) slightly and finding the signal with the tuning knob, watching the meter to see if the signal continues to increase in strength. Eventually, you will come to a point where the signal does not get stronger and in fact will start to get weaker. When this happens, adjust (12) slightly in the opposite direction from how you were turning it to find the peak again. At this point, the 580 kc signal may not appear exactly at 58 on the dial. That does not matter. What you have done is to align the set's oscillator to track properly with the set's IF chain. This step is important for best operation of your radio. After doing this, repeat the 1500 kc adjustments to get the dial spot on at 150 on the dial. As I said, 580 may not come in exactly at 58 but if the "rocking" procedure has been done correctly, the AM band will be tuned for its best performance with the set's oscillator tracking properly with the set's IF.

Is yours a Code 121, or 125?

[FStephenMasek]

Ron, your explaination of the goals and procedure for "rocking" to set padding trimmer capacitors is the best I've seen.

I'm going to sell the 38-116 when it is finished, but wanty the dial to be well-calibrated, or as well as is reasonably possible on any of them I restore, no matter if I plan to keep or sell them.

Did you notice that the schematic calls for the signal generator on maximum output, just the opposite of most radios where the goal is prevent AVC from interferring. The treble/expansion needs to be full clockwise, and the "magnetic tuning" off. The voltmeter is connected to one output tbe plate & cathode. Indeed, it would be impossible to use a digital meter for alignment. I've got a beautiful giant dial Hickok VTVM, but most often use my RCA Senior Voltohmyst.

[Ron Ramirez]

Thanks for the kind words, Stephen.

I just looked up both 38-116 Service Bulletins (codes 121 and 125), and yes, I see where Philco says the output meter should be connected between plate and cathode of one of the 6L6G outputs. Connecting your output meter across the plates of both output tubes will also work in any set with push-pull audio output tubes.

I see also where the instructions call for the "Attenuator" control of the signal generator to be set for maximum output in both Bulletins. This has to be a mistake. If you set your signal generator to blast its strongest signal through the radio, between the AVC and the overloading of the extra strong signal, you will never be able to achieve optimum alignment.

I use an old Clough-Brengle signal generator with a B+K frequency counter hard-wired to it, and I have found that if I turn it much more than 1/4 turn above minimum in terms of output from the generator, it will overload the radio under test. Other generators may vary.

Using the weakest possible signal from your generator will prevent AVC from coming into play, as you correctly pointed out.

I use an oscilloscope for alignments, and have used one for years now. But you can achieve the same results with any good analog VOM or VTVM.

[jerryhawthorne]

I bookmarked this one. Thanks to both of you. I'm still working on a 38-116 and could probably use some better alignment, very clear as to the approach. I have another post on my problems although the radio works well but I may have the mag tuning alignment figured out with the various problems I have had. A bad switch for the muting, a bad switch for the muting for the mag tuning using the speed dial. Then perhaps ( it appears) a miss wiring on the can of 3 caps that that kept the whole thing shut down. I must say the radio works really well.

Jerry