5. Output Transistor(s). Properly working output transistors should get warm after a few minutes, and if the radio is equipped with two of them they should both be the same temperature. The output transistor(s) can fail, typically from a short, in which case they will stay cold to the touch. The emitter lead wire (actually a special type of resistor) will appear burned up on the shorted transistor. If the radio has two output transistors, the second lead will burn up as well due to overload. Always replace both output transistors at the same time, even if only one is bad. You can use modern silicon PNP transistors (NOT the more common NPN type!) as replacements, if you feel confident with this level of repair. Otherwise, send the set to a radio guy. Germanium PNP transistors are also now available on ebay. On the radios with two output transistors, it is CRITICAL to use identical transistors – ensure that every marking on the two transistors is identical. Mount them with mica washers and silicone heat conductive grease to a clean aluminum surface. If the emitter wire has burned open, it is OK to shorten it to no less than 90% of its original length via a splice or added wire, but you must do this to both emitter leads.

If you use silicon PNP replacement transistors, a critical part of the installation is to set the bias (either via the adjustable bias resistor near the transistors, or replacing the fixed bias resistor if so equipped). You will need to adjust the resistor substantially to obtain the recommended 80-100ma of collector current needed for the new transistors. If a fixed resistor is used, solder it securely to the underside of the circuit board after cutting off the original. Use a 1 watt resistor (½ watt is ok if over 1000 ohms). To set the collector current via the bias adjustment, tie both transistor cases together via a jumper and connect a DC meter from the jumper and cases to the two leads removed from the case screws (two leads shorted together). Adjust the bias to a reading of 80-100ma on the meter. Failure to do this will result in overheating of the junction as you cruise along and – poof! - you are back to ground zero with burned out transistors!

One advantage of using the germanium transistors is that the bias adjustment may not be necessary, which saves time and effort.

6. Printed circuit board. The circuit board can crack or break right at the connection of a heavy component such as the audio transformer or the e-cap can. This causes strange events, especially sensitivity to vibration as you hit a bump. You often cannot see the crack in the board! Best remediation is to carefully re-solder the connections and mounts. Use caution – the board is old.

7. Power switch. Usually on the volume control (potentiometer). Replace or jumper the switch. If you jumper the switch the radio will be on all the time. No different than modern Mopar radios in that regard – you can turn down the volume (or mute) but cannot turn them off.

8. Tubes (aka “valves” ). The 1955-56 radios were tube powered. The 1957 -62 radios were all hybrids – tube powered with transistorized audio output. The 7 button AM radios remained hybrids through 1964. The 5 button radios became 100% transistorized starting in 1963. The AM-FM radios were all 100% transistorized. 90% or more of the time the original tubes are still good. Generally speaking, tubes are the LEAST likely of your radio problems. When you power the radio up, check for light inside the tube as the filament heats up. Some tubes are dark or opaque; in that case feel the tube for warmth on the surface as the tube heats up (allow 5 or more minutes). A tube with no vacuum will get warm but will not light up. Substitution of a good used tube is the easiest way to check a suspected bad tube. Used tubes are available on ebay.

The tube pins can corrode and oxidize in the tube sockets. Remove all the tubes – use care and remove gently – a very small screwdriver under the glass may help lift the tube from the socket. Being too aggressive can also damage the old circuit board on which it is mounted. Slow and steady wins the race here. After removing the tube, clean the pins with Scotch Brite. Straighten any bent pins. Using a Qtip or toothpick, apply a little silicone dielectric grease to each pin. Reinstall each tube all the way into their correct sockets.

9. Dial Lights Replace the dial lights (if so equipped) with new ones. The 1960-62 radios used Electroluminescent dial lighting. You can check the EL lighting by connecting the lead to the EL system in the car. A properly operating EL power pack is required. The EL radio dial lighting does NOT light up unless the radio is turned on, with the headlight switch on.

10. Search Tune feature on 7 button radios. Fuhgeddaboudit. On the 1960-64 Bendix AM 7 button radios, they went and spoiled a great set with a poorly designed power tuning system with the reliability of a Chevy Vega. Or maybe worse. These radios use a complicated snap over reversing switch that can break mechanically and cannot be repaired – the contact leafs just snap off. The best advice is to give up and cut the wire to the motor, or just avoid pressing the “local” or “distant” buttons. The radio will work fine and dandy using manual tuning. It is possible to replace the system with modern IC's and a relay – but huge effort – and maybe a 50% success rate as the motor or clutch is often bad. The motor seizes, and the electric clutch wears out, or fine wires inside the power drive clutch break off. These are excellent radios for sound and sensitivity when “right” - enjoy them by tuning manually. And they look cooler in your F/G/H/J/K than the 5 button radios, right?

11. 1F tuning transformers. The IF (intermediate frequency) caps are located inside square aluminum cans (typically 2 of them) mounted on the circuit board. These cans contain mica sheets with silver on them and are open to air. You know what happened to grandma's silver when it sat out – it tarnished! The silver in these cans does the same thing – turns black over time – and manifests as weak pick up and jumping volume on bumps. If you determine that an IF transformer is bad, the best answer is to send the set to a radio guy or get a different radio – these are very difficult to fix. Some old tube radios – notably Zeniths – had such a problem with these silver mica transformers that the antique radio guys coined a term for it: “silver mica disease.” The radio would sound like a terrible lightening storm was occurring – on a clear, sunny day.

12. Radio alignment. The radio service manual or Sam's Photofact will contain a complicated, very EE centric procedure for “aligning” (i.e. electronically tuning and calibrating) the radio using a signal generator and other special equipment. This is beyond the DIY skill set unless you are a certified “radio guy.” However, with the AM radios you can “align by ear” and possibly get better results than going through the gobbledigook (that's a technical term) procedure in the manual. We have already discussed the antenna trimmer earlier, which is the final alignment step. The IF transformers can be adjusted, if you have the correct radio alignment tools (available on ebay), although the alignment points are not always easily accessible. See your Photofact or manual for the layout and location. The Bendix radios have two easily accessible, screwdriver adjustable, variable capacitors on the chassis that can be adjusted by ear for optimal results. One for the oscillator and the other for the RF. Tune the radio to a weak station around 700 – 800kHZ and begin with the OSC (oscillator). This one should not require much, if any, adjustment. Then adjust the RF. That one may improve reception through adjustment to the left or right. Adjust for maximum signal/volume. Here is a photo of these components in a 62 seven button radio. You can also see one of the IF transformer cans on the left side of the photo.


On the Delco AM-FM sets from 1963-65, it is risky to attempt to align the FM section “by ear” - or for that matter on any FM radio or stereo. FM alignment must be precise and is tricky – best left to a professional radio guy.

13. Tuner section. Leave it alone! Do not EVER take apart the tuner, as the setting of the tuning slugs and tracking is impossible without elaborate test equipment.