![]() ![]() Of course, I do not have any spanner wrenches. The earphone jack had a nut on it that required a special tool – a spanner wrench. To proceed with the repair, I needed to remove the circuit board from the radio case. I doubted that it was the battery, but since it is the easiest thing to try, I replaced it. As they age, they dry out and require replacement. The variable capacitor acts to vary the capacitance (or electronic charge) by moving plates within the component, as the tuning wheel is adjusted.Īn Electrolytic Capacitor holds a charge, essentially like a small in-circuit battery. The Variable Capacitor, located behind the larger white adjustment wheel, is part of the tuning circuit. This surface gets dirty and needs to be cleaned to operate properly. Potentiometers, also known as variable resistors, have a small wiper that moves across a resistive surface. The Potentiometer, located just behind the white on-off / volume control (at the top of the radio), gets dirty over time. There were AM and FM, but mostly in large stereos with turn tables and large speakers built into a nice furniture type case. Other than the battery, the most likely issues are: 1) the ‘potentiometer’ for on-off / volume control is dirty 2) the ‘variable capacitor’ for station tuning is dirty or 3) an ‘electrolytic capacitor’ on the circuit board has dried out. ![]() Since this is one of the few items that I’ve had since childhood, I decided that I needed to perform a repair. With a set of batteries installed, I started up the radio and it seemed to work great, as you can see in this video that I took.Until a couple of months ago, this 1961 transistor radio had worked flawlessly. ![]() There is only one electrolytic capacitor in this set (100uF 12V, the round metal can next to the speaker) and it tested OK in-circuit, so I wasn’t going to replace it just yet. I also took this opportunity to clean all of the controls and switches with contact cleaner. In most cases, at least the power supply. Battery holder installed (left), and with batteries fitted (right). Using vintage radios generally requires inspection and repair or refurbishment before they can be safely operated. The battery holder then simply clips into place, and fits into the case. Circuit board with battery flying lead replaced. I simply replaced the original fixed battery leads with a PP3 snap-in battery clip lead, by desoldering the original cables from the circuit board, and soldering in the new ones (taking care to ensure that they were installed in the correct location). Replacement battery holder versus the original. I actually managed to source a replacement battery holder with roughly the same dimensions as the original which seems to fit well into the same space, and features a standard PP3 battery connector (which is typically used on 9V cells), making it removable. It seemed to be a somewhat standard design, holding six four 1.5V AA alkali batteries in series, providing 6Vdc to the radio via a power switch. The original battery holder was pretty much irreparable, so I cut it out and threw it away. On inspection, the radio had suffered battery leakage in the past, which had left remnants in the case interior and had severely corroded the battery holder, to the point where one of the terminal cables had been eaten away completely. If you’re interested in how “superhet” radios work, “ Transistor Superhet Receivers” by none-other than Sir Clive Sinclair himself is an excellent book. The S-74 is a reasonably simple six-transistor superheterodyne radio receiver, powered by four 1.5V AA batteries, with a channel switch and an internal antenna. Ajax Commander S-74 transistor radio before restoration. I bought it in unknown condition from a YMCA charity shop in Middlesbrough for £25.00, with its original box, user manual, warranty card, and headphone. I’ve been wanting to get into vintage radio restoration for some time now (after watching YouTube channels such as the excellent Mr Carlson’s Lab), as I find the electronics fascinating. A few months ago I bought my first ever vintage radio, a 1970s Ajax Commander S-74 “solid-state” AM/FM set, which is among the oldest items in my collection. ![]()
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