22 April 2018

Inside the Radiomarelli RD-160

My journey into the wornderful world of valves (tubes) has taken me in front of a 5-tubes radio receiver from 1955: components looked different back then!

Without a wiring diagram I've had to reverse engineer the circuit starting from the tubes. Large-ish cylinders are the possibly leaky capacitors. Two of them have like "melted" their caps: I will replace all five. I am in doubt about the large dual electrolytic, and it will stay for now.

Inside RD-160 - original!
In order to reconstruct the wiring diagram I took a picture of the circuit, cut it on the computer to show only relevant parts, increased brightness and printed it out on A4 paper. This way I can add notes on paper while I understand which component is which. I wanted to print it in B/W, just borders, but it wouldn't be easy to distinguish between components on different layers.

Three out of five "suspect" capacitors have lost their markings. I will chop them off so that their leads will be used as support for replacements. The capacitance meter confirms their expected values, within 20%. Still, I don't trust them.

Now waiting for the order to arrive. I chose replacements rated for 630V and I bought packs of 10, just in case I will step into another valve radio to restore (I want one with the wooden case!).