Audio Repair
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General Repair Tips for the Marantz Model 2235 - 2235B
The Marantz Model 2235 2235B is a classic receiver that was first introduced in the 1970s. It is known for its high-quality sound and durability, but like any electronic device, it can experience issues over time. Here are some general repair tips for the Marantz Model 2235:
Power Issues (Won’t Turn On)
- Check the Fuse:
Start by inspecting the AC line fuse on the back of the unit. If it’s blown, replace it with one of the same rating (typically listed in the service manual or near the fuse holder). A blown fuse could indicate a deeper issue, like a shorted power supply component.
Sound Issues (Distortion, No Sound, etc.)
- Check Connections:
Ensure all speaker and input connections are secure. Loose connections can cause sound issues.
- Inspect the Speaker Protection Relay:
The speaker protection relay can sometimes fail, causing no sound or distortion. Listen for a clicking sound when the unit is powered on. If you don’t hear it, the relay may need to be replaced.
- Clean the Controls:
Dirty or oxidized controls (volume, balance, etc.) can cause distortion or intermittent sound. Use a contact cleaner to clean these controls.
Power Supply Caps:
- Power Supply Caps:The large electrolytic capacitors in the power supply (often C801/C802 on the P800 board) degrade over time. If the unit hums or doesn’t power up reliably, consider replacing these with high-quality equivalents (e.g., Nichicon or Panasonic caps). Look for bulging or leaking caps as a visual clue.
- Check Switch:These can get dirty or worn. Spray some contact cleaner (like DeoxIT) into the switch and toggle it several times to clean the contacts.
One Channel Silent or Weak
- Preamp vs. Power Amp Test: Use the “Pre Out” and “Main In” jacks on the back. Connect the Pre Out to another amp’s input. If both channels work, the issue is in the power amp section. If one channel is still dead, it’s likely the preamp or earlier stages.
Sound Issues
Speaker Protection Circuit
- Check the Relay: The speaker protection relay can fail, causing no sound or distortion. Listen for a clicking sound when the unit is powered on. If you don’t hear it, the relay may need to be replaced.
- Inspect the Circuit: If the relay is fine, inspect the speaker protection circuit for shorts or open connections.
- Replace the Relay: These models have a speaker protection relay that can wear out over time. A failing relay may prevent the speakers from activating or cause intermittent connection issues. You can clean or replace the relay if necessary.
- Test the Circuit: After replacing the relay, test the speaker protection circuit by connecting speakers and playing audio. If still noisy, inspect output transistors or capacitors in the amp section.
- Output Test: Connect test speakers and play audio. Check both channels at various volumes. If still noisy, inspect output transistors or capacitors in the amp section.