Question on MPX-65 to WX Conversion

[mrphilco]

For Dave G., Joe, or anyone else:

When converting an MPX-65 MPX decoder to function as a WX, just how important is it to replace R216 and R221 (22 megohms) with 10 megohm resistors? Or can I get by with the 22 megohm resistors?

I ask only because it is so darned difficult to get to those resistors!

I am currently working on one MPX-65 and plan to convert a second one. One will go into my FM-100, the other into my 100-T (Coronet) tuner/preamp. Both tuners have blank plates meant for Crosby decoders to be installed in them.

Thanks in advance for any/all help.

 

[dcgillespie]

Leave the 22 Meg resistors in. I have a WX chassis here that came with 22 Meg resistors installed from the factory. The original value of 10 Meg or 22 Meg will work fine with 12AT7 tubes in the WX chassis, while the 22 Meg is needed to create enough bias headroom with the 12AX7 in the MPX-65 chassis.

Dave

 

[mrphilco]

Thanks, Dave, very much appreciated. That will make the conversion much easier.