Problem with the cassette player on a Marantz 4025

[davx975]

I have a problem with the cassette player on a Marantz 4025.
The problem is the signal from the cassette player is very very weak. I have to turn the volume to almost max to be able to hear the audio.
I cleaned the play/rec switch several times, checked all the wiring, including the head, cleaned the head, but still the same.
I'm planning to do a full recap on the tape preamp board.
Any advice on how to proceed and what to check next?

 

[Mooly]

Very hard to say without basic checks being performed. Do the VU meters deflect normally on playback of a known good cassette ? If so then the problem is either in the final stages of the audio circuitry or even external to unit. Have you tried the unit on another amplifier ?

If the meters do not deflect much then it sounds like a problem with the head/head preamp.

Are both channels the same ?

 

[davx975]

Thank you for your reply.

I have not tried the unit on another amp as it is an integrated tape player/recorder.

The VU meters do not deflect normally either. Both channels are the same. When I resoldered the head connections I intentionally left unsoldered one channel and touched the wires and the buzz was also merely audible. So I presume the head is ok.
I'll start with the head preamp.

I attached the tape preamp schematic.

 

[KatieandDad]

As both channels are exhibiting the same fault it's likely to be something common. I notice that the 30V supply is switched, that might be worth checking.

 

[Mooly]

The buzz should be huge when touching the head wiring, even with it connected to the head.

Supplies as K&D suggests are the first thing to check (that applies to any faultfinding).