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Bakelite Block number 3793-R Help Please for a 80JR - Printable Version

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Bakelite Block number 3793-R Help Please for a 80JR - Philco281989 - 09-18-2013

Hi guys,

I am re-stuffing a black box for the Philco 80 JR I am restoring. I cant seem to find a part number with values for 3793-R. The block (Part number 3793-R) ties into one section of the power transformer and wire wound resistor. Pre run #5 sets had two separate black boxes that contained .01 mfd in each one), I have run 7. After run #5 both blocks were replaced with a single black box that has a substitute .015 section combined with (#32), part 3793-R.

Does this mean that there is a .01 mfd and a .015 mfd in the black box or are they twin .015 mfd's. If it is a .01 and .015 I don't know which lugs to tie it into?

Thanks for your help, after this block restoration I will be ready for a first power up, so I am anxious to figure this out so I can fire her up tonight!

Thanks for your help.

Jon

RE: Bakelite Block number 3793-R Help Please for a 80JR - Radioroslyn - 09-18-2013

If those caps are going from the chassis to one side of the AC line and from the chassis to the power resistor (develops bias voltage for the 42 tube). .01 or .015 are fine value isn't critical.
Terry

RE: Bakelite Block number 3793-R Help Please for a 80JR - Jim Dutridge - 09-18-2013

The 3793-R was replaced with a 3793-OSU, a single .015 mfd @ 600 volts.

RE: Bakelite Block number 3793-R Help Please for a 80JR - Philco281989 - 09-18-2013

Jim, I see what you mean but this is a twin capacitor block. Radioroslyn, if I were to use the .01 and .015 do both go to common ground, I think the .01 attaches to lug 6 and ground. .015 attaches to lug 3 and ground.

I wonder how to set them up in the Bakelite block.

Thank you both for the help.

Jon

RE: Bakelite Block number 3793-R Help Please for a 80JR - Radioroslyn - 09-19-2013

Don't know that it matters. Just for the heck of it when you get it working take an electrolytic cap and connect the + side to the chassis and the - side to WW resistor/Pwr Trans junction. Value not too critical anything from 5mfd up @ 25v or higher. What should happen is a small drop in hum and an increase in the audio level. My point is that the .01 or the .015 arn't large enough to make much of a difference. The other cap on the pri of the PT just make the chassis hot with 110v ac depending on which way the power cord is plugged in to the wall.
Terry

RE: Bakelite Block number 3793-R Help Please for a 80JR - morzh - 09-19-2013

These are the Y-caps, the filtering of the line to the chassis.

1. Make sure you only use Y-rated capacitors. This ensures you don't get killed, and the caps don't become "killer caps".
2. Safety standards were different back then. The leakage, or the touch, current depending on what standard is applied can be required not to exceed 0.5mA to 3.5mA.
10nF makes it 1.28mA peak which is 0.9mA RMS. Won't kill you but will be sensed if you are grounded. 15nF will make it 50% more.

I use 10nF ceramic Y-rated caps.