Area of B Voltage Divider - How should wiring look?

[Ken Carr]

The wiring in the area of my B voltage divider has a few problems.

A loose wire is connected to the 100 V tap. There may have been a replacement resistor attached to this (broke away early on). The B+250V terminal attaches to a 'blob' of solder (blob-right) that joins several wires. There is also another blob to the left that is not attached to the B divider but is just a floating connection for several wires.

If anyone has a photograph from the same perspective as mine (see below) please be so kind as to post it. I just need a little help in putting this area back together again. I realize that I will have to trace everything but a photo of the correct physical layout may be helpful.

Thanks!

[Norman S Braithwaite]

The end lug with no connection should be ground.  It may be internally grounded.  Check to be sure.  On my set, the ground wire and shield of the umbilical cable is connected to this lug.  On my set the next lug, 100v, has one wire to the circuit and the other goes to one of the 4-mfd capacitors in the 4x4 capacitor block.  The other terminals have multiple wires attached.

Norman

[Scott Seickel]

Someone made a real mess. 

I think your divider resistor is completely backwards. 

I see yours is part number 523, and I have an early Philharmonic with the same part number divider.   Unless these dividers are symmetrical, which I doubt, then the terminal that is further away from the group of 4 should be your +250V. 

[Ken Carr]

Norman,
I thought it might be ground too but it is totally isolated .. no continuity with chassia ground. Maybe the wiring internal to this is what makes the odor when I add power (it is somewhere in this area).
Which is the 4 mfd block? There is an electrolytic that had 4 caps that are 4 or 5 mfd (not near the radio at the moment).

Thanks for the photo.
Norman S Braithwaite said:

The end lug with no connection should be ground.  It may be internally grounded.  Check to be sure.  On my set, the ground wire and shield of the umbilical cable is connected to this lug.  On my set the next lug, 100v, has one wire to the circuit and the other goes to one of the 4-mfd capacitors in the 4x4 capacitor block.  The other terminals have multiple wires attached.

Norman

[Ken Carr]

Scott,
That's exactly what I thought originally. I thought the 250V B+ was on the left and since it had no connection someone may have rerouted the B+ to that solitary loose resistor I found. But the terminal on the far right has exactly the resistance specified by Rider for a late set (I believe I have a very late set). The other resistance readings are close except for one. If you look at the photo in large size you will see my readings. Thanks for the photo.
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Scott Seickel said:

Someone made a real mess. 

I think your divider resistor is completely backwards. 

I see yours is part number 523, and I have an early Philharmonic with the same part number divider.   Unless these dividers are symmetrical, which I doubt, then the terminal that is further away from the group of 4 should be your +250V. 

[Scott Seickel]

OK.  So I disconnected my 523 divider and measured the resistance between each section.

Starting from left side in my picture, and measuring each section- 4 in total I get:

2.265K

441 ohm

436 ohm

1.34K

My set looks basically untouched with the exception of a few replacement capacitors that looks like they were done in the 1950's or maybe the 60's.    It is a 7 knob dial pointer, but the part number is the same as your therefore it should be correct for your set also. I would disconnect the wires you have, label them, and measure the resistance to match mine.  These B+ dividers are often bad.  Yours looks like it is in backwards anyway and the last tab is not grounded.

[Bill Liers]

I needed to replace the one in my last set as the high section was intermittent. The measured sections are close to yours Scott. I used an Ohmite 5K 50 watt unit to keep things cool. A couple of extra taps gave me the screen voltages needed. (tabs were covered with shrink after). You can see the ground tab at the one end of the original piece.

[Norman S Braithwaite]

Ken:

There were two configurations for the B+ divider resistor.  The late version used much finer wire for the last section increasing the resistance of this section to 1700-ohms (nominal) from 1200-ohms.  Consequently the spacing of the lugs is different with the last section of the late version using finer wire being substantially shorter.  Yours is correct for the late version and in my opinion it is installed in the correct direction.  The resistance of this divider should be checked out of circuit.

Norman

Ken Carr said:

Norman,
I thought it might be ground too but it is totally isolated .. no continuity with chassia ground. Maybe the wiring internal to this is what makes the odor when I add power (it is somewhere in this area).
Which is the 4 mfd block? There is an electrolytic that had 4 caps that are 4 or 5 mfd (not near the radio at the moment).

Thanks for the photo.
Norman S Braithwaite said:

The end lug with no connection should be ground.  It may be internally grounded.  Check to be sure.  On my set, the ground wire and shield of the umbilical cable is connected to this lug.  On my set the next lug, 100v, has one wire to the circuit and the other goes to one of the 4-mfd capacitors in the 4x4 capacitor block.  The other terminals have multiple wires attached.

Norman

[Ken Carr]

At Scott's suggestion I removed all leads to the B+ voltage divider. The photo that follows shows my resistance measurements between the terminals. They are very similar to those Scott got except that the far right terminal (far left as found in my radio) is entirely open, not connected to anything.

Here are my resistance readings for the photo below from left to right with Scott's in parentheses: 

2.70K (2.265K), 519Ω (441Ω), 416Ω(436Ω), and Open (1.34K).

I suspect that Norm is correct in that my orientation is as it belongs. The problems may arise from a couple of things:

- the terminal on the right in my original photo is not grounded at all. There is not even a ground lug. I suspect one of the wires attached to the terminal is acting as the ground.

- the terminal on the far left of my original photo is open but should show resistance. I suspect that as it heats up the resistance goes down and then it heats up so much that it starts to smoke and then I turn the radio off. It may be a bit like a toaster.

So,  I may have to make an arrangement like Bill Liers has with a substitute resistor tapped at several places

(My radio is an AM only, BOL late model Philharmonic - as best I can determine)

[Norman S Braithwaite]

These resistors suffered from poor internal connections hence increase in resistance or open sections.

Norman

[Ken Carr]

I just figured out how they grounded this thing. The terminal that should have a ground lug (see above one with bare wire attached) has been soldered to the case. It grounds through the mounting screw. Unfortunately the back of the case is a sliding piece that is part of the circuit path so it can't be reliable. Also when I removed the back cover of this unit I found that masking tape is attached behind the 'OPEN' post. Maybe they were trying to hold it together?

[Scott Seickel]

I think it was in backwards, and probably why it smoked when you powered it up, though it is a moot issue at this point.

Look at the left side of the (Ken's) picture above- you can see where someone removed the ground that would have been bent over to the leftmost terminal. This terminal was connected to B+ in your set which I believe is incorrect.

Not only that, the pic Bill Liers posted is of the same set as Ken's- a 9 knob red dial set- and it shows that the B+ terminal is the one that stands alone. The part numbers are the same for all of these.

So can the late configuration for this resistor be the one where there are 3 terminals grouped in the center of the resistor, and the end terminals are spaced further away?

[Ken Carr]

 I suspect that you have it right, Scott. It looks like I will be in the market for a 5K Ohmite like Bill used.