[fenbach]

The electrolytics, nos. 60 and 62, on the Rider schematic for Model 37-620 look backwards to me.

http://www.nostalgiaair.org/PagesByModel...013212.pdf

And opposite to those [nos. 66 and 69] on the schematic for the 37-640

http://www.nostalgiaair.org/PagesByModel...013216.pdf

Which is right?  Or possibly both??  Or does it matter???

[462ron]

The schematic for the 37-620 electrolytics 60 & 62 are wrong. The schematic for model 37-640 electrolytics 66 & 69 are correct but cap# 66A is wrong. The negative should go to the PT center tap and the positive to chassis ground!

Ron

[Radioroslyn]

I don't know that I see anything "wrong" with the two different designs. One uses a cap to filter the negative leg of the power. One cost a little more but so does the set.

[Chas]

Neither schematic identifies filter capacitor polarity using "+ or -"..

However the "draftsman" uses the symbol of a bar inside of a cup, a symbol intended not only to represent a liquid filled electrolytic but also its polarity, the bar is the "+" and the cup is "-". The wrong schematic has the symbols upside down (connection), not only a polarity error but the electrolyte will run out

[Radioroslyn]

To be honest I don't look at the outside edges or whether it's cupped or not to determine the polarity. They all look like non polarized jobs and I just figure it out.

[JimSirt]

I can't tell you how many times I have come across this capacitor symbol being incorrectly illustrated in this manner and like Terry, I just find the appropriate ground points and move on but this is the first time that I have seen this pointed out where the misuse of this symbol is also a causing serious secondary violation of the most basic fundamental in physics.
Will have to keep an eye on this moving forward. Thanks Chas, made my day

[RodB]

It's such a simple thing to put a plus in the correct place then there's no question to debate.

Great comment on the electrolyte leak, Chas. Good Monday morning pick-me-up.

[Chas]

It has been so long ago that I serviced a chassis and turned it over to have some of the electrolyte actually run out of the condensers... Yeech...

There was only the smallest standardization of symbols used in schematics. Often a radio brand could be recognized by seeing just a portion of the schematic. RCA had some quirks in early battery sets in using a diagrammatic, then using fillets on lines followed by tube elements numbered within a circle. Tuning condensers often indicating the rotor.

The practice of introducing new symbols as electronics evolved has become more common. Ideally, a "device" schematic should follow a flow of some sort.

For "our" radios signal left to right, impedance high at top and low at bottom of active devices and support (power) feeds under active devices, power sources some lower left some in the lower middle most in lower right.

All that is often confusing when trying to follow signal paths in a diagrammatic, that, is the pictorial of the schematic represented by actual component placement.

In a very recent post in ARF was of a convoluted PA and power supply. More like a corn maze...

https://www.antiqueradios.com/forums/vie...6&t=432631