EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

AW 23 Chassis deviations from the schematics....

As I've been going through the various sections of the chassis, I'm noticing parts which were in place since day one which deviate from the print. The capacitor variations have been discussed, lots of .1 mfd capacitors on the print which are actually .05 in the units. That really wouldn't seem to be a big change in any of the circuitry before the audio section. From the audio stages onward, you might notice a little more bass. But what seems odd are the resistor changes. There are several factory ones which do not match the print and likely would affect the circuit. Notably, several around the RF section.  The latest was R386, 2Meg on the print that's a 3Meg in the chassis, I've found several like this. Has anyone else noticed this as well? Curious if the changes were production improvements or just parts substitutions.


Views: 127

Reply to This

Replies to This Discussion

I have encountered such deviations but have not taken much note.  The Allwave Fifteen chassis are loaded with deviations from the published schematics.  EH Scott Radio Laboratories incorporated minor improvements throughout the model runs without publishing updated schematics.  There is one resistor deviation of note in the AW-23.  That is a 500k ohm resistor across the primary of the last IF included to slightly reduce Q and gain of the last IF.  This resistor is not shown on any schematic, is included in every chassis of which I have inspected, and was likely included to prevent regenerative oscillation in the IF circuit.


Hi Norman,

So far, I've noticed several changes in the RF section, also the grid resistor on the oscillator is 100K (should be 75K on the schematic), and the suppressor grid resistors on the 39/44 IF tubes are 5K (1K on the print). The list of changes is getting long. Seems reasonable at this point to just replace part for part what is in the set. The situation is a little more tricky when I've come upon parts that aren't factory and need to know what Scott specified.


Justin - The 0.1 to 0.05 capacitor change was noted in one of the service bulletins. Scott did issue a few service bulletins in this timeframe, there are some significant changes discussed in them. However, even those do not account for all the differences you have encountered. As Norman said, Scott did incorporate changes as things went along, and even if the schematics at the factory were updated, they typically didn't republish them. I would take the approach you stated...replace things with what you find in the set, and when you run into conflicts or questions, post here and we'll try to help you with it. I have several chassis to look at to resolve questions. Good luck!


Reply to Discussion


© 2023   Created by Kent King.   Powered by

Badges  |  Report an Issue  |  Terms of Service