This page only covers how to align an AM radio, which is the easiest to align and requires only basictest equipment. FM radios are much more complicated and require highly specialized equipment to align. Getting Started First of all, alignment should only be performed on an AM radio that has been recapped and is *working*! It is never a troubleshooting technique and will not correct problems caused by shorted paper capacitors, faults in the power supply, OTR resistors, &c! Alignment be performed if components or wiring in the RF and converter sections were replaced, or to improve the reception of a fully-restored radio that is to be used for daily listening. Although I have heard some people say to "alignment should only be performed by 'experienced' repairmen," the only way to get such "experience" is by actually doing it. Alignment can be practiced on a simple 5-tube AC/DC receiver before attempting to align more elaborate models with RF stages. The principles behind alignment is simple. The IF transformers are all adjusted for peak response at the radio's designed intermediate frequency, often 455 kcps. Then the tuning capacitor in the RF section is adjusted so that the dial reads correctly. Finally, the oscillator of the converter is set to produce a frequency that the difference (or less commonly, sum) of the intermediate frequency and the radio frequency to which the radio is tuned. If the radio employs an RF stage, there will also be an antenna matching circuit which is adjusted for peak response too. Before attempting alignment, be sure you have all necessary tools and equipment. AM alignment requires the following test equipment: a voltmeter to use as an output meter, a modulated signal generator (described on the Equipment page), and an isolation transformer for transformerless radios. If you plan to get serious in restoring AM radios, I recommend an oscilloscope as well. You will also need a set of alignment tools—I recommend AES's "CB Alignment Tool Kit" Part #S-T18-530, as it will contain tools for all radio types, from large "slot-type" tools for early radios to hexagonal types for later models. If possible, get the service literature for your radio too, as it will contain any special procedures that are to be followed. A frequency counter can also be handy if your signal generator does not have a digital display on it or if you have reason to doubt the calibration accuracy of your signal generator. Oscilloscope or Voltmeter? Some high-end antique AM radios with RF stages, like the RCA 2-X-61 for instance, will list "cathode ray alignment" in their service guide, and give connection information for an oscilloscope on their schematic. Usually they instruct to connect the oscilloscope to the AVC line; the oscilloscope servicing as the output indicator during the alignment procedure instead of an AC voltmeter. If so, then it is strongly advised that you use this method over the "output meter alignment," as it will only be given if there is some particular advantages to it over the conventional AC voltmeter across the speaker coil. Usually it means alignment on that particular model is especially critical, for instance if narrowband IF transformers are used to achieve a sharp response or if "tight" (precision) L-C tracking across the full band is required. If this is used, the oscilloscope can be of any type, as wide bandwidth is not required. Be sure the coupling on its vertical amplifier is set to "DC" as this is you will only be Although this is a six-tube superheterodyne (uses a RF amplifier). an isolation transformer must be used. so it will be necessary to readjust the oscilloscope's vertical sensitivity to keep the trace visible as the stages are aligned. along with the required alignment tools. Procedure The picture above shows the Zenith 6L03 chassis.interested in the DC component of the AVC signal. 50C5. I am also using an HP 5315A . the IF transformers are of sufficient bandwidth that alignment is not as critical as it on models like the RCA 2-X-61. The following procedure is given for it in its service manual: Operation Connect Oscillator to: Set Dummy Input Signal Dial Antenna Frequency At: Trimmers Purpose 1 Converter Grid 0. signal generator (Smart-Kit 303). The one I used is part of my dim-bulb tester. 6BJ6. as you can visually see the radio attempting to cut gain on strong signals. Using this method also gives a better indication of potential overloading.F. This includes the following: service manual from Nostalgia Air. The Zenith L622 uses chassis #6L03 with tube lineup 6BJ6.5 µF 455 kcps Adjust 600 Primary & kcps Secondary Slugs For I. and connection cables. Alignment Example I recently aligned my Zenith L622 clock-radio to serve as a good illustration of the alignment procedure start to finish. alligator clips. as the service literature will give any special instructions that must be followed. digital multimeter (Simpson 467). 12AT6. The AVC voltage becomes more negative for stronger input signals. which is hidden underneath the table. Being as this is a transformerless model. Note that this is to serve as a general guide. Alignment 2 One Turn Loop Coupled Loosely to Wave Magnet [Loop Antenna] -- 1600 kcps Oscillator Set Oscillator to Dial Scale Detector Alignment Align Antenna Stage 3 4 -1400 kcps -- Detector Antenna Preliminary Setup This picture shows all the necessary equipment. 12BE6. 35W4. the tools must have tips exactly the correct size (to within a fraction of a mm) to turn the slugs. which carries the RF signal. The IF transformers in this Zenith radio happened to be bizarre exceptions to those aforementioned standards. a slightly wider tool is needed. This is pin 7 on the 12BE6 and is marked with an (A) on the schematic. Then I noticed an unusual illustration in the service manual. what was going on here?! Was only one side of the IF transformer tuned? No." but with no hole on the bottom. I wish I had an endoscope probe so I could have gotten an "inside" view of these strange things! The slug for the upper winding is hollow and has a slightly wider cross section than the lower one. shown to the left. Notice the cables and adapters I am using. it uses the postwar "style. which is behind the DMM. and fixed inductors. This is an example of why I recommend getting a *good* set of alignment tools like the kind listed above. used to prevent the tube's bias voltages from passing into the signal generator) to the grid of the pentagrid converter tube. 50Ω coax like RG-58 should be used for as its impedance matches that of standard signal generators. . Being made in 1953. but this is not required. Post-WWII models used variable-core inductors and fixed silver-mica capacitors built into the base. the core for the primary is accessed from the top and the secondary from the bottom. just one at the top! Huh. not the first or local oscillator grid. which of the tube's grids? Connect to the third grid. The alligator clips are connected through a capacitor (in this case ½ µF. Wait. Generally on postwar types. the schematic clearly shows both primary and secondary are tuned. PreWWII models generally used ones with air-variable trimmer capacitors. Thus the lower one is accessed by slipping a slightly narrower alignment tool down through the upper slug all the way to the bottom of the can! To adjust the top one. The output of the signal generator is taken through an RG-58 coaxial cable to a pair of binding posts to which the alligator leads can be connected. Although it doesn't matter much for low frequencies like the AM broadcast band.frequency counter. which were accessed from the top for both primary and secondary. Adjusting IF Transformers There are two main styles of IF transformers. Now turn the radio on and allow it to warm up for a few minutes. On coils like these. I am also using a binding-post-to-BNC connector so that I could quickly connect and disconnect my frequency counter. The signal generator is connected to the clips. The multimeter is set to AC volts and connected across the speaker. as this will cause the adjustment to change the moment you let off of it.Now set your signal generator to 455. So try not to push down upon the screw with the blade of your alignment tool when adjusting them.) If the radio is already in fair alignment this process will go quickly. it will be necessary to reduce the signal generator output several times to prevent overloading as the system gradually nears alignment. and the far one is for tuning the antenna matching circuit. the signal generator will be connected between that input and the metal chassis. as the IF stages are now aligned. Increase the output of the signal generator until you hear a squeal in the speaker. "Coupled loosely" means to have the coil in the same orientation as the loop antenna and held slightly above it. However. the middle one is for the "detector" (tunes the third grid of the pentagrid converter to the RF signal from the RF amplifier). Now it is time to get the RF section into alignment. as will be the case if some dummy randomly "fiddled" with them in the past. Radios without an RF amplifier will just have two trimmers to adjust. For radios with loop antennæ. so it can be put aside. then peak its primary. and so on until you get to the primary of the first IF transformer. The trimmers for my radio are shown to the left." the amount of force applied to them determines their capacity. to start with the secondary of the last IF transformer. As described in the service guide. if the radio is badly out of alignment. Keep the output of the signal generator low—just enough to get a good indication on the voltmeter. . the signal generator will likely be connected to a one or two turn coil of 22gauge wire loosely coupled to the radio's loop. the large flat-head alignment tool will be used to adjust the mica trimmer capacitors on the tuning capacitor. The capacitor that was used is also no longer needed. (Repetitions are sometimes needed because high-gain tuned amplifier stages may interact with one another. For this step. For radios with external antenna inputs. no force should be applied. as little adjustment will be required on the transformers.0 kcps or whatever your radio's intermediate frequency is (this will be given in the service guide). Be aware that these mica trimmer capacitors work by principle of "compression. And then you repeat this procedure until no further improvement in signal level can be obtained. Adjust the IF transformers for maximum response. The usual recommendation is to start at the back and work your way to the front: that is. the one nearest the shaft is the adjustment for the oscillator. This step will vary somewhat depending on the radio model. Adjusting RF Section Turn off the radio and disconnect the alligator clips that were connected to the converter section. You just want to move the screw of the trimmer inwards or outwards. such as L/C tracking adjustments done at some low frequency like 600 kcps. There should be a mark of some sort here if the dial scale is not attached to the chassis. near the far end of the MW broadcast band. Adjust the oscillator trimmer for peak response. like 1. For elaborate AM or shortwave radios. Just as with the IF alignment. now the oscillator should track with the dial setting.Once you have your signal generator coupled properly to your radios RF section. it may be necessary to repeat these steps for RF alignment a time or two in case there is any interaction between the circuits. Now you want to peak the input side of the converter. Once its RF section was nearing alignment. as the squeal from the speaker will be a blasting roar with the volume turned up! I have found that this can often be the case with the SK-303 signal generator. way off in a room on the opposite side of my house to obtain a sufficiently low output! Such extreme measures are unlikely to be required if you are aligning a simple 5-tube set. This may be done at a different frequency than the oscillator tracking adjustment. as the FCC requires AM stations to keep to their assigned frequency to within extremely narrow limits. There. Depending on the sharpness of your radio's response. set the one-turn coil down under my table.) Once I aligned an RCA 2-X-61 that I had to get really creative with. and rotated it until it was at a right angle to the loop antenna. Remember to keep the output of the signal generator low. turn the radio back on and allow it to warm up. Like for this particular Zenith radio. there may be some addition steps that are performed.400 Mcps in this case. Congratulations. just as in the IF alignment! For tube radios with RF stages. try using an off-air station for these steps. for they are often so extremely sensitive that they are overloaded even with the signal generator output turned down as low as it will possibly go. I found I had to connect the signal generator to a short piece (~30 cm) of wire and set it way. A mark is provided on this radio so that the dial can to accurately tuned to this. Set the signal generator and the radio's dial to 1. (This puts the laws of electromagnetics on my side. as it was designed for more modern AM radios that are much less sensitive than high-end tube radios. I turned the signal generator's output down low. you may have to get inventive here. Both accuracy and precision are crucial in adjusting these stages. as it blocks the magnetic component of the field of the antenna that holds most of the power radiated. If the accuracy of your signal generator is unknown and you don't have a quartz-referenced frequency counter to use as a reference. you align the antenna matching section for peak response in the case of sets with RF stages. you may have to "hunt" a bit until you pick up the squeal of the signal generator. You will likely know if the level is too high.600 Mcps. Final Steps Lastly. your AM radio is now in proper alignment! . but these will be easy and straightforward. and allows only a portion of the weaker electric component to pass through.