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Philco Battery pack 41-8007 - Printable Version

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Philco Battery pack 41-8007 - Guest - 03-11-2008

Has anyone on the phorum ever taken one of these apart,or is a schematic of
the battery pack available?Am rebuilding a 38-38,and am using a AC pwr supply;would like to keep the 2 volt tubes,however the biasing of the audio stages has me in a puzzlement.The -9 vdc for the 1H4G driver tube is returned to gnd via a 900 ohm resistor in series with a 1 meg /100k resistor to the grid of the 1H4G-the -9vdc is applied to the junction of the 900 and 1 meg resistors.Now is this battery pack one continous battery that is tapped or are there separate "B" and "C" sections?
Tnx es 73 de Bill W4NJF

- Ron Ramirez - 03-12-2008

Hi Bill

P9068 was a later (1946) replacement for the B and C battery used with Model 38-38. It was rated at 135 volts for the B supply, and 9 volts for the C supply.

There is a fellow who used to post here frequently, who is great at building power packs and making them look like authentic vintage batteries. Maybe he will see this and chime in.

Philco 41-8007 - Guest - 03-13-2008

Hi Ron,
If I'm reading the schematic right,the 900 ohm resistor in question is placed in parallel with -9vdc section(via the on/off switch) when the radio is in operation-quite a load on that battery!The AC pwr supply I'm building is actually on the radio chassis itself and is intended to eliminate all the batteries.I plan on using a voltage divider off the center tap of the B+ supply to chassis ground to develop the the negative bias voltages for the audio stages.What I need to know is this 900 ohm resistor necessary with this configuration?
73 de Bill

- batterymaker - 03-14-2008

The 9068 is a LARGE BC pack that consists of 9 volts C and 135 volts B--all tapped at various points. The B and C are separate but share one point--I believe it's Negative B and Positive C. Attached are pix of my repro and the original catalog photo.

Bill


[Image: http://users.mw.net/~bmorris/bcpack.jpg]
[Image: http://users.mw.net/~bmorris/finishedbcpack.jpg]
[Image: http://users.mw.net/~bmorris/bcpackinnards.jpg]
[Image: http://users.mw.net/~bmorris/farmpacks.jpg]

- batterymaker - 03-14-2008

Here's the socket hole layout and its associated voltages:

[Image: http://users.mw.net/~bmorris/bcpacksocket.jpg]