These next two pictures were taken before any work was preformed on this receiver. They show the components that were found underneath the chassis. This Hallicrafters S-77 was just slap full of cobwebs and insect remains. It must have sat on a shelf or up in an attic for many years before it found its way here.
The photograph on the left is of the RF deck. The picture on the right displays many of the waxed paper and molded paper capacitors that make up the circuitry of the S-77. These capacitors are often found to be the source of trouble. It is usually recommended that all of these capacitors along with the electrolytic capacitors be replaced. The reason being is that over time the old capacitors may start to dry out and become open, shorted or leak which can hurt the performance of the receiver and possibly cause serious damage to some of the major components. Some times when I do these restorations I actually drill out the gunk from inside of the old electrolytic capacitor and stuff the new replacements inside. I normally do this so that the radio would keep its original appearance. Capacitors that are made today are not only sturdier and more precise, but are also much smaller. A capacitor from yesteryear that was the size of a roll of quarters is now the size of a pencil eraser today. In most cases, the new replacement capacitors will easily fit inside the body of the old capacitor. Some folks have been known to take this a step further and go so far as as to even stuff both the waxed paper and molded paper capacitors to give the set a museum quality restoration. Before I solder any wires or leads to the chassis or to the tube pins, I clean the oxidation and other gunk from the connection point with a Dremel tool using a wire brush attachment.
In order to do an alignment on this receiver the technician will need just a few basic service tools. These items include a signal generator which must cover the frequency range of the S-77 including 455 KHz, a non-metallic screw driver and a standard RMA(Radio Manufacturers Association) dummy antenna. The RMA dummy antenna consists of a 0.0002 MFd capacitor that is in series with a 20 uH RF choke. The choke or inductor is shunted by a .0004 MFd capacitor in series with a 400 ohm non-inductive resistor. The RMA antenna sounds more complicated then it really is. Please click on RMA Schematic for details on this antenna and why it should be used.
The first step in the alignment procedure is to turn on the receiver and the signal generator and allow each of them to warn up and stabilized. Around a half an hour will often suffice. The next step is the proper setting of the controls on the front of this receiver. Set each of the controls as follows, sensitivity and volume is set at maximum, the AVC and Noise Limiter is turned off, bandspread at zero, CW/AM is set to AM, standby/receive is set on receive, and the tone control is set on high.
There are normally at least two alignments that must be preformed on a receiver. It is important to always do the IF alignment first and the RF alignment last. This receiver is no different and the IF alignment is preformed first. The IF of this receiver is 455 KHz. The chassis will need to be removed from the cabinet to preform the IF alignment. The RF alignment is just the opposite and should be done with the chassis installed inside of the cabinet. Access to preform the alignment is done through holes in the bottom of the cabinet. The reason it is done this way is because the calibration of the oscillator will be slightly effected by changes in the capacity between the cabinet bottom and the RF coils and wiring.
With all that done lets begin. The receiver should be set to band one and the dial set on 1 MHz. Tune the signal generator for a 455 KHz modulated signal and connect the positive lead to the stator plates in the center of the tuning gang and the negative lead to the chassis. Adjust coils A through F for the loudest audio from the speaker of the receiver. Adjustment points B, D and F are made from the top, while the rest are accomplished through the bottom of the cabinet.
For the next step we now need to set the signal generator to produce a 455 KHz unmodulated signal and set the AM/CW switch to the CW position. All of the other settings are the same as above. Once done, remove the pitch control knob from the front of the receiver and adjust point G which is the shaft from the pitch control for a zero beat. Once done, replace the knob but be sure to put the dot on the knob in the center position of the tuning range of the pitch control.
The RF alignment is just as easy but a touch more tedious. It involves changing the frequency of the receiver for each band and matching this frequency with the signal generator. There will be a total of eight frequency changes that will need to be made, two for each band. One thing to keep in mind is that it is some times helpful to run through each band a second time for a final tweaking which will yield superior receiver performance before moving on to the next band.
Lets begin, receiver functions should be set as described above. Connect the RMA dummy antenna to terminal A1 and make sure that there is a jumper between A2 and G. The ground lead from the signal generator is connected to the chassis. Set the band switch to four and tune the receiver and signal generator(modulated) to 36 MHz. Now adjust points H, I and J located on the bottom of the receiver for the loudest audio from the receiver's speaker. Once done, tune the receiver and signal generator to 18 MHz and adjust points K, L and M located on the bottom of the receiver for the loudest speaker audio.
Now we move to band three and tune both the receiver and signal generator to 14 MHz. Next we adjust points N, O and P on the bottom of the receiver for the loudest speaker audio. Now we move to the other side of the dial and adjust both the receiver and signal generator to 10 MHz and adjust points Q, R, and S which are also located on the bottom of the receiver for the loudest speaker audio.
Moving right along we now set the receiver to band two and adjust it and the signal generator to 5 MHz. Once done we adjust points T, U, and V which are found on the bottom of the receiver for the loudest audio from the receivers speaker. Once done, we next set both the receiver and signal generator to 1.8 MHz and adjust point W that is found on the bottom of the receiver for the loudest speaker audio.
The last two steps in our RF alignment takes us to band one. Tune both the receiver and signal generator to 1.5 MHz and adjust points X, Y, and Z that are found on the bottom of the receiver for the loudest speaker audio. Are you ready to finish this job? Excellent, tune both the receiver and signal generator to 600 KHz and adjust point Z which is found on the bottom of the receiver for the loudest audio from the receiver's speaker. That's it, you are now done. Did you notice how the adjustments followed the alphabet?
All of the adjustments above will need to be done with the non-metallic screw driver. For safety reasons, do not preform this work alone or if you are tired. It is not worth your life.