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

[Jay Forbes]

I see I repaired another Philharmonic. 
Attached is a pic of readings made of its B- voltage divider. 
Seems the current one is way off....

[David C. Poland]

Jay - my experience, those old B+ voltage divider units Scott used are no longer very  reliable. I had one more than one like yours with one bad section and by the time I had the bad section bypassed, another failed. I replace the whole unit with a 40 or 50 watt rating.

Consider replacing your entire unit with an OHMITE ceramic resister with the exposed wires and several adjustable taps. I can't locate my specific notes, but a unit about 8K or 9K ohms is a good place to start and what I keep for this use. Measure the good sections of the old one now before you start heating up any part of it. 

You will probably need to take voltage readings to adjust the new unit attain the proper voltages 

Also, the top left rear rectangular unit between the pair 6L7's and 3rd AF 6J5's is the bass tone reactor which has 4 caps inside to replace - failure to do so may cost you the bass control pot -  unwire the leads, dismount the module & then extract the pair of chokes inside holding the 4 caps.

The nearby soldered box holds 7 caps to replace - all are .5 (not .05).  

[Chris Wysong]

Here is another topic talking about the Ohmite resistors in the Philharmonic.

My apologies. This is for the B+ divider and you are looking for the B-

https://ehscott.ning.com/forum/topics/need-assistance?commentId=392...

[Scott Seickel]

In circuit resistance measurements are 40, 50, 60, 148 and 260 ohms. 

[Jay Forbes]

From my comment above, readings on another Philharmoic I repaired was:

40 ohms, 20 ohms, 20 ohms, 85 ohms, 120 ohms

With voltages: -3 vdc, -4.5 vdc, -6 vdc, -15 vdc and -27 vdc

So this seems to vary quite a bit from Scott's measurements...

[Jay Forbes]

Your measurements were taken from chassis ground to each terminal?  If so, they match pretty close with mine in comment below yours.

Scott Seickel said:

In circuit resistance measurements are 40, 50, 60, 148 and 260 ohms. 

[Scott Seickel]

The measurements I posted are from EH Scott technical reference and were "in circuit" measurements.  I don't have easy access to a set at the moment otherwise I would measure one. 

[Scott Seickel]

It is very possible that the negative bias divider changed in later production as did the B+ divider.  Which AM only set is this and the one you posted a pic of?  This divider resistor is normally fairly reliable unlike the B+ which is nearly always bad. 

[Jay Forbes]

Here is a pic from set I am repairing.  It also has a pot connected to it.  This set has the VR150 tube in front of chassis - not in the rear.

Scott Seickel said:

It is very possible that the negative bias divider changed in later production as did the B+ divider.  Which AM only set is this and the one you posted a pic of?  This divider resistor is normally fairly reliable unlike the B+ which is nearly always bad. 

[Jay Forbes]

B+ divider in this set is good.  One section of the B- divider is open and another section is suspect.  see pic below.  thx for the advice.

David C. Poland said:

Jay - my experience, those old B+ voltage divider units Scott used are no longer very  reliable. I had one more than one like yours with one bad section and by the time I had the bad section bypassed, another failed. I replace the whole unit with a 40 or 50 watt rating.

Consider replacing your entire unit with an OHMITE ceramic resister with the exposed wires and several adjustable taps. I can't locate my specific notes, but a unit about 8K or 9K ohms is a good place to start and what I keep for this use. Measure the good sections of the old one now before you start heating up any part of it. 

You will probably need to take voltage readings to adjust the new unit attain the proper voltages 

Also, the top left rear rectangular unit between the pair 6L7's and 3rd AF 6J5's is the bass tone reactor which has 4 caps inside to replace - failure to do so may cost you the bass control pot -  unwire the leads, dismount the module & then extract the pair of chokes inside holding the 4 caps.

The nearby soldered box holds 7 caps to replace - all are .5 (not .05).  

[David C. Poland]

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]

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.