[B1189WHW]

On my AVA FM-3, between the row of tubes in front and the transformer, the were two tube sockets.  One is empty but one tube socket remains - but it is empty.  Is there supposed to be a tube in it?

Thanks,

Bill

bwilson@tecinfo.com

[avahifi]

Assuming that your FM3 is actually working, the missing tube must be the chassis mounted rectifier tube.

If this is correct, then the rectifier tube has been replaced by a diode bridge mounted to the tube socket on the bottom side of the chassis.

If not, then the tuner probably is not in working order.

If the rectifier tube socket does have the diode bridge installed, then do not install a new rectifier tube

Note that tube information is printed on the bottom of the chassis bottom plate.

Frank

[dB Cooper]

Hmmm... it says 'AVA FM3' but IIRC the Audio Basics article on the FM3 said not to install a solid state rectifier b/c it would mess up the alignment. ?

[avahifi]

If we replaced the rectifier tube with a diode bridge due to lack of availability of the rectifier tube, we would have realigned the tuner after the change to take into consideration the somewhat higher B+ voltages from the diode bridge power supply.  The issue is not as serious with this old tube tuner as it is with a vacuum tube power amp where the increased B+ and instant B+ to the output tubes at turn on can degrade them.

Frank