EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

I'm rebuilding a 5 knob Allwave Imperial and noticed that while the schematic that I have shows most of the upper chassis paper capacitors to be .1mf I've found that most of (what appear to be) the original capacitors are actually .05mf.

Wonder if anyone else has seen the same thing and if so why the discrepancy?

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I have also rebuilt an all wave 23 and found something similar. I think it will depend on the schematic version you are using. I replaced all with .1 uf, except those that on the schematic were listed as .05 uf. In my case, all of the bypass caps were .1 uf, and one of the coupling caps in the audio section was .05 uf. There are at least 2 different schematics for the Allwave 23, early and late. Mine is the early version. 

Thom

EH Scott Radio Laboratories initially produced the AW-23 using Potter 0.1-mfd capacitors then switched to Sprague 0.05-mfd capacitors. There is no difference in performance of the receiver but a slight difference in cost of replacement components. Oddly, the Potter 0.1-mfd capacitors are smaller in diameter than the Sprague 0.05-mfd capacitors and the holes through which the IF decoupling capacitors passed were sized for the original capacitors employed.

Norman

Thanks for the Info Thom and Norman.

In this set I've found that most of the .05s that I've replaced so far are black Mallory TP series but it looks like the diode and IF bypass Caps are tan and might be Spragues. Also the .13 Caps on the power Amp attenuator board were all Potters.

All of the paper Caps appear to be original to the set but sometime over the years the dual voltage regulators were replaced by an octal OC3 tube and the electrolytics were replaced. Both jobs were very professionally done and I'm thinking they may have been done at the factory or by a local factory representative but without documentation who knows...

Anyway, Kent - In case you're following the SNs are Y-392 upper and C459 lower.

Again, Thanks for the Info.

-Tony

I am in the process of rebuilding a 7 knob AW-23 and have also found .05uF Sprague capacitors in all of the locations shown on the schematic as .1uF. It would seem that I need a different version of the schematic. So far I have been unable to locate a schematic that matches my chassis. There is also a 1uF 200V capacitor that I don't see in any of the available chassis pictures or on schematics. Attached picture identifies the location of this part. Has anyone else come across a unit with this capacitor.

 

Scotts were custom built upon receipt of a purchase order and, so, the AW-23 chassis on your bench may reflect evolutionary changes during the 2 year model run - so it is unwise to modify original looking work to match a diagram. 

There was a factory bulletin that advised when an AW-23 receiver chassis is in for service, to replace the many .1 caps with higher voltage .05 caps. I use modern .05 at 630 volt film caps. About the only receiver chassis caps of another value are in the tone (bass) control. Maybe yours 7 knob is late enough production to have been built with the .05 caps.

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