Philharmonic B- Voltage Divider - One Section Open

[Jay Forbes]

In the 5 section B- voltage divider on a Philharmonic I am repairing (no FM), one of the sections is open.  From Ground of this divider (left) to right (full B-) resistance readings are as follows:

62 ohms,  45 ohms,  45 ohms,  600 ohms, OPEN 

What is the value of the OPEN section of this divider ????

thx

[Scott Seickel]

Those pots were original on later Philharmonics.  I assume you have a beam of light set and not a dial pointer.  How many knobs on the front?  Does it have the red writing for the TV band?

The C- dividers are pretty reliable compared to the B+, but one problem is that the connections to the resistance wire inside can become poor and the resistance of a section increases, or opens. 

Jay Forbes said:

So the pot was a repair?  It looks original.

David C. Poland said:

My B- divider evidently failed soon after production. When acquired 50 + years ago, it had already been replaced by discrete resistors, which does include the pot in your photo.

[Jay Forbes]

Riders has the Resistance Values of the B- Voltage Divider (values between sections):

from Ground Side: 40 Ohms, 10 Ohms, 10 Ohms, 88 Ohms, 112 Ohms 

Power calc for each section is less than 2 watts, so 2 Watt resistors would be the minimum value.

Riders also has the Resistance Values of the B+ Voltage Divider (values between sections):

from Ground Side:  2,200 Ohms, 430 Ohms,  420 Ohms,  1,200 Ohms 

Power calc for each section is less than 10 watts, so 10 Watt resistors would be the minimum value.

I had missed seeing this info until just now...

[Scott Seickel]

The Riders shows the values of the later divider.  There was more than one version.  Your dial pointer most likely has the earlier version.   Best thing to do is use the proper variable tapped resistor and adjust the voltages for proper value. I posted the best Ohmite replacement part number for the B+ divider and you should be able to find it via a search. 

Jay Forbes said:

Riders has the Resistance Values of the B- Voltage Divider (values between sections):

from Ground Side: 40 Ohms, 10 Ohms, 10 Ohms, 88 Ohms, 112 Ohms 

Power calc for each section is less than 2 watts, so 2 Watt resistors would be the minimum value.

Riders also has the Resistance Values of the B+ Voltage Divider (values between sections):

from Ground Side:  2,200 Ohms, 430 Ohms,  420 Ohms,  1,200 Ohms 

Power calc for each section is less than 10 watts, so 10 Watt resistors would be the minimum value.

I had missed seeing this info until just now...

[Jay Forbes]

I used the values in Riders and voltages were all high. 

Then I read the NOTE that if B- is more than -28 Volts to add a shunt resistor.  My  voltage was -33V so added a 1200 ohm 2W shunt resistor to get down to -28 Volts.  This brought all the voltages to proper levels.

Scott Seickel said:

The Riders shows the values of the later divider.  There was more than one version.  Your dial pointer most likely has the earlier version.   Best thing to do is use the proper variable tapped resistor and adjust the voltages for proper value. I posted the best Ohmite replacement part number for the B+ divider and you should be able to find it via a search. 

Jay Forbes said:

Riders has the Resistance Values of the B- Voltage Divider (values between sections):

from Ground Side: 40 Ohms, 10 Ohms, 10 Ohms, 88 Ohms, 112 Ohms 

Power calc for each section is less than 2 watts, so 2 Watt resistors would be the minimum value.

Riders also has the Resistance Values of the B+ Voltage Divider (values between sections):

from Ground Side:  2,200 Ohms, 430 Ohms,  420 Ohms,  1,200 Ohms 

Power calc for each section is less than 10 watts, so 10 Watt resistors would be the minimum value.

I had missed seeing this info until just now...