First of all, please be patient with me. I'm 17 and just starting out in electronics. I read (more like skimmed, to be honest) several books about electronics and have a decent understanding of the basics. I also have been reading this forum for months now and have watched a number of useful videos on youtube. Now I'm embarking on my first project, a Motorola 57W purchased cheaply from eBay. It is a basic mid-50s 5-tube AM-only tabletop radio which I thought would be a good beginner's project. I plugged it in and it does work which is a nice surprise since it was advertised as for parts or repair. I have a few questions that folks here can probably answer (sorry if any are stupid questions). Four of the tubes are Motorola, of which two I know for a fact are original based on their 1956 date stamps and the other two Motorolas are probably also original. The fifth tube is an RCA replacement with no date stamp, but it has the newer/current RCA logo so perhaps that narrows it down a bit. Does anyone know when they started using that logo? Also I notice several of the tubes have a black blotch on the inside of the glass. I was just wondering if this equates to high hours? I don't have a tube tester, but since the radio works I do conclude all the tubes are good or at least serviceable for now. The underside of the chassis is loaded with paper capacitors, so I won't be running it anymore until those are all replaced. One cap is a huge red one with four wires which, based on Mr. Phil Nelson's site, I have identified as a multi-selection electrolytic capacitor. Does four wires mean I will have to replace it with three separate caps with one shared ground wire? I'm not going to proceed with replacing caps until I buy a photofact schematic, but just wondering. Last thing, the knobs are pretty dirty and one is especially nasty. What's the best way to clean them without causing damage? They're plastic, that's all I know. Sorry this is long and thanks for the help..
11-29-2016, 10:27 PM
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