Marantz 2225 FM Issues

[lazio2000]

Calling all Marantz and FM "lovers" to try to decipher a familiar scenario that I have already seen on model 2230.

1) FM Signal strength meter barely moving (not even one line).
2) Center tuning meter (discriminator) centered and when tuning from station to station moving slightly left & right.
3) Plenty of good FM stations, good selectivity, great audio quality, but low amplitude in comparison with AM, I would say one third.
4) Signal strength meter working properly.
5) Scoped signal at output of P200 (pretty small).
6) When pressing the muting button, no audio whatsoever.
7) No stereo light whatsoever.
8) Tried changing the FET on P100 (no changes), seems FM front end works fine, just weak.
9) Tried new Demodulator (no changes).
10) Starting to suspect a weak P200 IF strip ????

Any suggestions welcome, thanks

 

[Punker X]

Could be a ceramic filter or bad transistor. Try to tune into your strongest station. You should see signal through the filters, with a loss. Can also check in and and out of the transistor and see gain. I have seen the a bad transistor in the IF section of this vintage Marantz. Transistor is probably more likely that a filter.

 

[lazio2000]

Could be a ceramic filter or bad transistor. Try to tune into your strongest station. You should see signal through the filters, with a loss. Can also check in and and out of the transistor and see gain. I have seen the a bad transistor in the IF section of this vintage Marantz. Transistor is probably more likely that a filter.

Thanks Punker.
Further troubleshooting has determined that:

1) The P100 FM front end is in good shape. I disconnected it from the IF stage and sent the output signal into another IF Amplifier from a separate Pioneer tuner, and the results were perfect with strong audio and good stereo separation.

2) I am attaching transistor voltages taken at P200 & scoped output at pin J205.
This rig is done with the equipment I have (B&K RF SG E2000).

3) No test has been done on the ceramic filters. I tried swapping H205 without any results.
I have gone back on some old posts about the tubular capacitors inside the choke coils going bad. Placing an small exterior ceramic capacitor in parallel causes the signal meter to increase the strength slightly.

4) I am suspecting a defective P200 not producing a strong enough signal to trigger the P300 etc......

5) Another strange behavior is that the FM trimmer capacitor screws on top of the tuning capacitor, that are normally very touchy, have no effect on the signal or frequency.