I picked up a National RQ-3001S at a car-boot sale last weekend, cosmetically it's in great shape, for something that is older than myself, I believe these are from around 1969. It works, to an extent, but I'd like to try and make it work better. Initially, the play button was stuck forward, so the pinch roller was up against the capstan, so there is a groove embedded in the rubber. Looking closely at the rubber, it looks like it is a thin rubber "sleeve" around the main pinch roller bulk. Is it easy to get a new rubber "sleeve" for the pinch roller? I was also attracted to the unit because of the single button that does play, FFWD and REV. Like I said, it was stuck in the play position, but it was easy to get open (5 screws, no plastic clips!), and get to the mechanism to free it up. The belt is a bit loose, but the cassette will play and the speed sounds just about right. However, one of the biggest problems is the sound, although it does play the sound, it is very low. I did clean the playback head, but that made no difference (and it looked clean anyway). It also doesn't fast forward or reverse tapes. The fast forward does activate (switches on), but doesn't turn the tape, or even the pickup reel with no tape inserted, I think because the belt is so loose. The reverse doesn't switch on, probably just a switch somewhere that needs to be cleaned. The mechanism is something that I'd never seen before, it doesn't look like it uses gears/cogs, but more like rubber surfaces on wheels, and belts to engage. I'll look into it more later. So the main thing is the volume, when up at full, it is very low, and does reduce when turned down. Would it be a head issue, or some other components, capacitors maybe? Anybody work inside these before, or similar models?
The older models are all built like tanks, lot's of sliding metal plates held together with screws and springs. Lubrication is either gone or dried which makes the moving parts stick. Parts are only found on "parts units" and because it's a mono piano key tape deck, finding parts decks might be hard, there's not a lot of collectors for these units. If you look at automotive hardware you may be able to either make a new rubber sleeve with plugs (vacuum caps) or better yet, find some tubing that will fit over the roller. I was going to experiment when I get some time to find a good way to modify rubber for these uncommon sizes. I was thinking about either using a metal lathe or a drill press. I'm pretty sure they sand or grind down the rubber and don't cut it, so I'd start with sanding blocks to get the outer diameter to size. I've seen photos of people doing it with a hand drill, that might be an option if you don't have shop equipment. If your not familar with Techmoan on YouTube, he loves old audio equipment, one of the common problems is low volume. I'd watch some of his videos to see what he does to fix it, personally I'd start with some DeOxit in the volume switch but once you get into 60's and early 70's units you may have to swap out some capacitors at minimum. https://www.youtube.com/channel/UC5I2hjZYiW9gZPVkvzM8_Cw
