Vintage audio restoration with service manual reference
I was lucky to get a truly nice old piece from my uncle - an ancient Grundig PA-2 amplifier! Now, I can't wait to bring it back to life and use it as an amplifier for my record player. Externally it's pretty good condition but can you believe it, when I switch it on, a small crackling noise comes from one channel and the panel backlight only works by turning it on and off. This means that the contacts must have been oxidized and the electrolytic capacitors are probably dead by age, that is, they cannot hold charge anymore. I'm not an expert, just a handyman, so I first looked for the layout diagram of the parts and later on found the whole service manual on manualmachine.com. It contains all the necessary voltage levels and part numbers for this type of unit. Plus, the info is very readable. The question is, do I dare to open the thing and resolder the leaky joints inside or do I just clean the dust and lubricate the volume potentiometers with a special contact spray? Has anyone here done the restoration of this particular Grundig series?
Man, you’re really lucky — those vintage Grundig amps have such a warm sound that you rarely find today! If I were you, I wouldn’t rush into resoldering everything right away. First, try cleaning the potentiometers with isopropyl alcohol or a proper contact cleaner — in most cases, the crackling disappears after that. The backlight issue is also pretty classic; it’s often just old bulbs burning out over time. How does it sound in the low frequencies, though? Does the transformer hum during operation? It might be worth replacing the main filter capacitors in the power supply section.