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38-116 Code 125 3-Capacitor Box on Top of Chassis - Printable Version

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38-116 Code 125 3-Capacitor Box on Top of Chassis - LarryFS - 09-05-2019

I've been slowly working my way through a 38-116 I acquired a couple months ago.  Item 65 in the parts list is an assembly of three capacitors (two 0.1 mfd and one 0.7 mfd).  This assembly is in a box mounted on top of the chassis (see photo).  I'm familiar with bakelite blocks but not this box.  Are the capacitors in this box potted as those in bakelite blocks are?  Are there any things I need to watch for if I remove this assembly from the chassis?  Can replacement capacitors be mounted under the chassis or are they boxed on top for shielding purposes?

Thanks for the help!
Larry

RE: 38-116 Code 125 3-Capacitor Box on Top of Chassis - rfeenstra - 09-05-2019

I recently finished my 37-116 with a similar cap. it was not that difficult to remove the old caps and install new film caps inside. I'm sure they were encapsulated but I believe it was wrapped in paper that made it quite easy to remove with a little heat.

RE: 38-116 Code 125 3-Capacitor Box on Top of Chassis - LarryFS - 09-05-2019

OK, I'll remove it and put new caps inside.

Thanks!

RE: 38-116 Code 125 3-Capacitor Box on Top of Chassis - morzh - 09-06-2019

I think it was wrapped in fish paper and only potted at the bottom so not hard to take apart.
I assemble all the caps, wrap it in new fish paper (if old is ripped), and then pot the bottom with hot plastic.

RE: 38-116 Code 125 3-Capacitor Box on Top of Chassis - LarryFS - 09-06-2019

It was certainly easier than a bakelite block!  

However, I'm not very good with schematics and am uncertain on how to connect the new caps.  There were 3 wires coming from the box.  One I labeled A and it went to a terminal strip connection point that also had one side of a 490K resistor.  The other two I labeled B and they went to an adjacent terminal strip connection point that had one side of the other 490K resistor.  Resistors are 64 and 88 on the schematic.  See photos.

Is the following correct?

1.  Connect one end of the .7 mfd cap to one .1 mfd cap and the other end of the .7 mfd cap to the other .1 mfd cap
2.  Connect same end of one .1 mfd cap to terminal marked A
3.  Connect same end of other .1 mfd cap to terminal marked B
4.  Connect other ends of .1 mfd caps together and to surface of can (chassis ground)

Doing the above means I only have two wires going from the box to under chassis connections.

RE: 38-116 Code 125 3-Capacitor Box on Top of Chassis - rfeenstra - 09-06-2019

According to the schematic, that would be correct, and yes, you would only need 2 wires coming from the can. This can was probably used in other applications that required the third connection. For this application, the 2 wire approach is less cluttered on the "A - B" terminal strip. When I get to my 38-116, I may do the same thing even though I did it as original in my 37-116. Why it was done with three wires probably can be answered by Ron or one of the other guru's!

RE: 38-116 Code 125 3-Capacitor Box on Top of Chassis - LarryFS - 09-06-2019

Thanks very much!