Welcome to Beoworld ! The belts will have blocked the motor and possibly a fuse has blown. Remove the remains of the old belts and see if the motor will run again. If not, the fuse will have blown. It's very common. I can supply new belts with mounting instructions etc. (and also a fuse if need be). Martin

[quote user="Rich"] Is this a speed selector relay? Do you have a capacitor kit for a BG4002 Type 5513? [/quote] Yes and yes. That relay is a known trouble-maker. I suggest you check it before you replace the trimmers again. Tap it gently while playing, just like you did the motor - or just replace it. Martin

Unstable speed culprits are normally : - Trimmers - Relay contacts (if your version has the speed selector relay) - Capacitors, electrolytics and tantals - Motor cleaning and lubrication While playing, tap the motor lightly with a pencil or similar. If it changes speed it will definitely need cleaning etc. Martin

Something mechanically bent or broken inside ? Is the tonearm parking position apprx parallel to the deck edge ? Martin

You can look at the tapeheads. If there is a gap between the two track elements of apprx the same size as the elements themselves, you have a 4-track. If the elements are close together, covering almost the entire tape width, it's a 2-track. A tape recorded on a mono machine will typically have one track playing fine with the other track playing

Yes, the stereo lamp is present but it doesn't have a proper holder. It's merely squeezed in and held by a rough piece of foam. There's no hole through the chassis for the wires either. Martin

OK, then try winding the tape to the other end and start playing from there. Martin

Callout 2 on the first diagram is a button to select between 2 and 4 tracks. I suggest you try this with your Sony tapes. Martin

And here, right next to the fuse where the service manual for the Master 610 shows no components, only holes, some components were obviously cut out Martin

No socket for a stereo decoder. But a decoder has been mounted nevertheless No threaded hole to accept the frontmost screw, which was then just left out And also lacking a threaded hole, the cooling fin for the external transistor just sits in with the wires Martin