Author Topic: 1959 Imperial Power amp question settings for the controls on it  (Read 414 times)

1959MagnificentMagnavox

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1959 Imperial Power amp question settings for the controls on it
« on: November 28, 2017, 09:25:37 AM »
Thanks guys for the capping help you gave me in the previous thread. It is all recapped and sounds amazing. On the power amp there are 3 controls, one says treb chan 1 treb channel 2 and the other is bass. I have both trebles up full, i had to actually back them both off a hair, as it was to much!
 i keep the radio controls timbre set at full and the treble set to concert and sounds fine now
the bass control on the power amp im confused, its this just a increase or decrease control or a bass balance control? i have seen this same power amp in pictures on here, some have a while paper with steps on it and a black control knob, mine has no paper or knob, just the white pot control stub.
my paperwork came with a paper telling about these controls and its hard for me to understand. a friend of mine has one that has the knob and paper i assume is a balance for bass. so is mine just a increase or decrease control? as of now its turned full to the right, or do i have it set as only the right channel having base lol???
Magnavox made so many tweaks and changes to things i dont know. I have bass but id rather have those controls set properly for best results :)

Mike

electra225

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Re: 1959 Imperial Power amp question settings for the controls on it
« Reply #1 on: November 28, 2017, 10:52:58 AM »
I have not had experience with the AMP-182 chassis.  But on the 8100 chassis (its successor) there is no bass control on the chassis.  Only treble controls for each channel.  I turn the treble amps completely down, then turn them up a couple ticks.  I run the treble control one notch from the extreme right position, the bass control full on, then vary the timbre control to get the treble where I need it.  Mine would sound like a clock radio with the treble amps turned up as high as you have yours.  It's good to hear you get it going okay.  Would you care to share specifics with what you did?  How many resistors did you change?  What was the condition of the cathode by-pass resistor?  Did you find gassy/shorted output tubes? 
If it ain't broke, call me.  I can break it....

1959MagnificentMagnavox

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Re: 1959 Imperial Power amp question settings for the controls on it
« Reply #2 on: November 28, 2017, 11:33:22 AM »
Hi

They were all changed, i had one 12at7 tube that was shorted and one rectifier that was dead, everything else tested very strong.

a friend of mine his amp has a bass balance knob and he was thinking mine was the same, but it does not say balance on it

so for now i have it full to the right. The two treble control's i turned full then backed them off to where i want them. having those full was to much. That timbre control more than has enough highs for what i need

electra225

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Re: 1959 Imperial Power amp question settings for the controls on it
« Reply #3 on: November 28, 2017, 01:14:55 PM »
Here you go, Mike.  This is how to set the bass balance on your amplifier. 


file:///C:/Users/user/Downloads/Magnavox%20_Balance_of_Stereo_Speaker_Systems_AMP-182.pdf


Hope this helps.  I'm glad the 8100's are not this complicated. 




Here is a reference to the schematic for anyone who would like to follow along.


file:///C:/Users/user/Downloads/Magnavox%20AMP-182BA.pdf


It appears to me like the bass balance control (a 200K ohm pot) is used in the input of the Channel 2 bass amp only.  Channel 1 has two 100K resistors that are fixed.  What they are doing exactly is still not 100% clear to me, but methinks this is another way Magnavox figured out how to make something simple complicated.  What appears to be taking place with this circuit is that stereo balance (bass balance) is accomplished with shop and test equipment rather than by a manual control.  Magnavox never did put a "real" balance control knob on its stereos, at least in the tube days.  They typically hid the balance control down the hollow shaft of another control that required a special driver to adjust.  They did not want John Q. Customer messing with their factory settings, apparently.  I personally would not mess with that balance control until I had read the instructions I posted and felt brave.  Fortunately, they improved this faux pas with the 8100's.  They got their own set of bad habits, though.  Good luck
If it ain't broke, call me.  I can break it....

electra225

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Re: 1959 Imperial Power amp question settings for the controls on it
« Reply #4 on: November 28, 2017, 01:52:08 PM »
I have no idea why the links I posted don't work.  My bad.


Basically just a balance control, connected differently than what is typically seen.  The more complicated adjustments are for external speakers (?).  I guess you can just use your ears listening to a mono source and go from there.  Good old Magnavox.......
If it ain't broke, call me.  I can break it....

voxACthirtee

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Re: 1959 Imperial Power amp question settings for the controls on it
« Reply #5 on: December 02, 2017, 11:48:36 PM »
In this amp, the fixed 100K resistors on one side of the bass channel are a simple voltage divider designed to knock the signal down. Voltage dividers with equal legs drop voltage 50%
The pot on the other channel is 200k so in the "middle" it gives you 2 - 100k legs. Otherwise it drops voltage more or less depending on position. So you are just able to "Match" the output of the variable channel to the fixed channel.