The PHILCO Phorum
Model 650 Tone Control Question - Printable Version

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Model 650 Tone Control Question - Hamilton - 06-27-2023

https://philcoradio.com/library/download/service%20info/wiring%20diagrams/vol1/split/Part87-Philco%20Wiring%20Diagrams%20Vol.%201.pdf

I’m working on replacing the caps on this 650 and the tone control has me confused. I know there are 2 - .01 caps and one 3000 mmf cap to go in there but I’m not sure how to wire them in properly. There are 4 wires coming out of the tone control, 3 of them are connected individually to the three lugs shown with the blue arrows on the photo. The 4th one is the red wire that leads to backelite block #63. 

If someone in the Phorum could assist me as the where the connections for my replacement caps should go it would be appreciated. 

I’m new and still learning this hobby and not real fluent in reading schematics. Thanks.

RE: Model 650 Tone Control Question - morzh - 06-27-2023

I am not home, so I cannot look.

Does anyone have Ray Bintliff's book available? They are all listed there.

Meanwhile, try Philco Repair Bench by Chuck Schwark; some are listed there.

RE: Model 650 Tone Control Question - Ron Ramirez - 06-27-2023

Here is a schematic drawing of your tone control. Notice the annotations added in red by me.

   

Now, in pictorial form, using your picture. Annotations in yellow added by me.

   

One end of the first .01 uF capacitor connects where you see .01 uF (1) in the photo. The other end of this capacitor runs, via a wire coming from the tone control body, to resistor (54).
One end of the 3000 pF (.003 uF, or if you prefer, 3 nF) connects as shown in the photo.
One end of the other .01 uF capacitor - .01 uF (2) - connects as shown.
The other ends of the 3000 pF cap and the .01 uF (2) cap connect together and run, via your red wire, to block (63) and to the control grid of the 42 driver tube.

RE: Model 650 Tone Control Question - Hamilton - 06-27-2023

Thanks Ron and Morzh for helping me out. That’s exactly what information I never. I love this hobby and the assistance provided by much more experienced members like yourselves make it that much more accessible to junior members like me.
Much appreciated!

RE: Model 650 Tone Control Question - morzh - 06-27-2023

Now that it has been resolved, a little hint:

This is the link to your radio sch on the Nostalgia (Riders-on-line)

http://www.nostalgiaair.org/PagesByModel/824/M0013824.pdf

As you could see, the values are shown in the sch, and two 0.01uF caps are symmetric relative to the 3,000 uF cap.
Considering, there are 3 positions on the switch.....are you pondering what I'm pondering?

RE: Model 650 Tone Control Question - Hamilton - 06-29-2023

I’m looking at Condenser Block 50 and it calls for 2 - .00011 caps and 50A a .00005 Mica Cap. Are these .00011 caps in the 50 block Mica caps and if they are should I just leave them alone. I do have 2 - 110pf Micas from Justradios if that would work in this block.

Not sure where part #50A, the .00005 Mica is located. 

Any assistance would be appreciated.

RE: Model 650 Tone Control Question - Ron Ramirez - 06-29-2023

(50)a is separate from the two (50) mica capacitors, not part of the (50) bakelite block. The schematic shows (50)a connected between the top of the volume control and its tap, this is where I would look for it first.

RE: Model 650 Tone Control Question - RodB - 06-29-2023

Hamilton, you normally don't replace the mica caps. The 2 in part 50 are mica and don't have to be replaced unless subsequent problems point to a failure.

RE: Model 650 Tone Control Question - Ron Ramirez - 06-29-2023

Actually, the two caps within bakelite block (50) are probably paper.

A majority of Philco bakelite blocks containing two 110 pF capacitors usually have paper caps inside. Of the literally hundreds of these I have restuffed over the decades, I can remember only one or two having mica caps inside.

Just replace the ones inside the block.

RE: Model 650 Tone Control Question - Chas - 06-29-2023

Quote:Hamilton, you normally don't replace the mica caps. The 2 in part 50 are mica and don't have to be replaced unless subsequent problems point to a failure.
I will second that restoration issue. Overall genuine mica condensers are "most" often found in tuning circuits. "Shotgunning" them is a real recipe for radio disaster...

Even, twisting them on their leads to read the "dots" risks fracturing the bonds to the metal foils internally as the copper wire extrudes during the twist moment.

The "best?" time to determine if there is a mica condenser problem other than split open, blistered, burned or broken lead wire is to; Complete the restoration and operate the radio. Poor sensitivity, dramatic calibration errors that cannot be "aligned out".
If the "desire" is so strong to discover, gently de-solder one lead wire and take a measurement.

One company MICAMOLD made both mica capacitors and paper caps under that name. As a "general" rule rectangular Micamolds are paper, starting value of .0001mf.

The square Micamold is mica values from less than .0001 down to FWIR 10pf. are mica and may also have temperature compensation, the dots tell the story Icon_rolleyes

GL

Chas

RE: Model 650 Tone Control Question - Ron Ramirez - 06-29-2023

Hello, is this thing working??? Icon_rolleyes

Again -

Most Philco bakelite block capacitors which contain 110 pF capacitors have tiny wrapped paper capacitors inside, NOT mica.

But don't believe me, I've only been in this game for 49 years and have restuffed literally hundreds of Philco bakelite blocks containing 110 pF capacitors. I've seen them. Seeing is believing.

But what do I know.

And with that - I'm out.

RE: Model 650 Tone Control Question - morzh - 06-29-2023

As Ron said:

The 110pF caps inside the backelite blocks ARE NOT mica caps, but ARE PAPER caps.

While they are not used in any place that could cause safety issue, they will be leaky as any paper cap, which could be easily determined by disconnecting them prior to gutting, and measuring with good meter (a DMM will not do, they typically are limited to 100pF, though you could use a Delta mode to compensate for the probes). So, the performance of the radio will be affected in an unknown way. Perhaps even unnoticeable.

But my personal rule is same as Ron's: if it paper, it has to go.

RE: Model 650 Tone Control Question - Hamilton - 06-29-2023

Thanks all. I will go ahead and put in the new caps. I have not fired up the radio yet. I’m still waiting for two tubes to come in. It was in rough shape when I got it so I’m taking my time and replacing all the caps first. I’ve made mistakes before so I’m going slow with this one. 
I believe it is a 650MX model with the tilt top lid on it. The veneer has to be fixed in spots and the tilt top was severely warped so it’s a daunting project for me.
Thanks for all the help.

RE: Model 650 Tone Control Question - RodB - 06-30-2023

Hey Ron, you're absolutely right about the micas in bakelite block. And it's logical, why would they put mica caps in the block? Thanks again for correcting that.

RE: Model 650 Tone Control Question - Hamilton - 06-30-2023

I’m finished with replacing all the caps and out of range resisters, which was all but three of the resistors. The one photo shows the caps that were replaced in block #50. They do say Micamold but I’m assuming they are paper underneath?

I fired it up and it is working but the volume is very low and does not increase when I turn the volume knob. The volume control is not original, photo enclosed. Could that be the problem of the low volume? As well two of the tubes, a 6A7 and one of the 78’s,  I received didn’t test very well on my tester. 

Any ideas on how to proceed would be appreciated.

Ron, I hope your still willing to help out. I respect your opinion immensely.