[simpsons]

May I suggest we go back to fundamentals.

First question, why were the wires around the EF86 burnt? and is this a clue as to why the sound levels are low?

Second, it was said after rewiring "Now the fault is low output." Does this mean that before the burnt wires were replaced the tape recorder worked? If so the fault condition has been caused by the rewiring.

If the machine wasn't working before replacing the burn wires then it's back to the first question.

Relay connection W1, from the schematic, either sends the record level to the magic eye on record or defeats the bias oscillator on playback. I'm not sure which wire you have disconnected but I don't believe this will help find the problem.

From the Instruction Manual, you can listen to recordings on the internal loudspeaker. In other words, use the Grundig Tape recorder as an amplifier. Does this work?

Chris