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
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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.
--
Ron Ramirez
Ferdinand IN
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
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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]
Posts: 104
Threads: 11
Joined: Oct 2005
City: Indianapolis, IN
Here's the socket hole layout and its associated voltages:
[Image:
http://users.mw.net/~bmorris/bcpacksocket.jpg]
