Can't find switch

[Joe Miller]

Still working on my AW23.  I can't seem to find the "radio/phono" switch on the set.  The switch shows as  a double pole sw on the schematic-- to remove the radio audio and insert the phono audio.  I also have a spare parts AW chassis.  I've traced the wiring from the phono post on both sets and it goes to the audio section (different sections I might add) but there is no switch? 

 

Anyone know where this switch is located?

[Norman S Braithwaite]

Joe:

Many of the interstage transformers are turning up open now.  The fix on your chassis is unusual and uncommon.  From a performance perspective, the fix probably affected a reduction in overall gain (not a problem given the fact that radio stations broadcast much stronger signals today and the Scott has more than enough gain) and affected more linear operation of the audio amplifier circuits in the receiver.  It would fall in the category of "improvement".

Norman

[Norman S Braithwaite]

If the "upload files" below this reply window works, here is the early version schematic.

Norman

[Joe Miller]

Norman,

Many thanks.  This should do me...

BTW, I noticed the phono connection penciled in --that's where I had planned to reconnect it. 

I also see a phono connection on the schematic on the cathode of the 6C6 1st AF.  My parts chassis is connected this way.  When the Scott phono switch (on the phono) is switched to phono the signal is applied in series with the 6C6 cathode and ground.  When the phono switch is not in phono, it shorts the input to ground as shown on the schematic you sent me.  I assume this is for a low impedance input phono signal??

I had planned to connect the phono as it is penciled in on the schematic (at the volume control high side).  That will cause a problem when the phono switch is not in phono since the volume control will be shorted to ground.  I assume this is the high impedance method for inserting the phono signal.  Right?

I'll check to see whether or not my Scott phono wants a low or high impedance input to the set.  If high impedance, I'll connect to the volume control and make sure to not put the phono switch in the position that shorts the phono input. 

If the Scott phono wants a low impedance input, I would need to connect to the cathode of the 6C6 as shown on the schematic, but my 1st AF has been modified in the cathode circuit to resolve the open interstage transformer.  So I need to think about it. 

Right now the phono on my good set (with the mod to fix the open interstage transformer) is connected to the cathode of the tuning meter amp (76 tube).  That won't work because when the phono switch is not in the phono position the tuning meter will be  inop.  But maybe it will work given the mod that was done??

Any thoughts or recommendations you may have would be appreciated.

Thanks for eveything,

Joe