Flip the tape monitor to Source before you buy a part. Wait on a recap kit if the radio and the record died together. On a Sony HP-510A from Facebook Marketplace, that switch was one of the reasons the first record produced crackle and no music. The rest of the order is the crackle guide.
Silence on every source
| What you find | What it means | What to do | Shop |
|---|---|---|---|
| Switch sitting on Tape | The deck loop is open and every source is muted | Set it to Source and try FM | View Switch sitting on Tape (affiliate) |
| Switch on Source, sound changes when you flip it | The contacts are oxidized | DeoxIT D5, then work the switch | View Switch on Source, sound changes when you flip it (affiliate) |
| Radio plays, record does not | The tape switch is not the fault | Check the stylus and the cartridge leads | — |
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What the switch actually does
The tape monitor sits after the function selector. In Source, the radio or the turntable continues to the volume control. In Tape, the stereo listens only to the tape-in jacks. Fifty years on, those jacks are empty, so Tape is silence with the dial still lit and the platter still willing to spin.
On this HP-510A the platter spins as soon as the tonearm moves, even with the selector on FM. That is how the motor is wired. It does not mean the selector is stuck between positions.
When the position is already right
A switch left halfway, or one that crackles as it moves, has dirt in the contacts. Unplug the stereo. A short burst of DeoxIT D5 into the switch, then 20 to 30 throws, is the fix that brought the left channel and the phono input back on this unit. The solvent is flammable until it dries.
If Source is selected, the switch has been cleaned, and one channel still crackles on every input, the fault is past this switch. That is the one-channel guide.