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 Post subject: RCA M-46 too much base
PostPosted: May Fri 04, 2012 1:25 am 
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Joined: Nov Sun 02, 2008 8:06 pm
Posts: 151
Location: Fredericton NB Canada
Working on this RCA M-46 I have recapped the set . Many caps were the waxed type . Few resistors out of tolerance and replaced . Awesome reception on all bands.The tone switch has 3 settings low mid and high. On the low setting base is awful. Mid range so so and the high range not to bad. I have swapped a few tubes with no success. This set has an electromagnetic speaker, some of paper was torn and repaired with service cement. Seems to be working ok . Kind of wondering if speaker is at falt as there is an awful vibration to the paper cone when the base freq are present. Here is a link to the schematic.http://www.radiomuseum.org/r/rca_victor_m46.html
I have not had a chance to do any voltage tests yet. Any Ideas of where to look ?
Thanks guys....

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 Post subject: Re: RCA M-46 too much base
PostPosted: May Fri 04, 2012 7:09 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 11441
Location: Albuquerque, NM 87123
The cone may be loose.

Did you replace the capacitors according to the schematic, or to what was removed from the radio?


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 Post subject: Re: RCA M-46 too much base
PostPosted: May Fri 04, 2012 11:45 am 
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Joined: Nov Sun 02, 2008 8:06 pm
Posts: 151
Location: Fredericton NB Canada
Caps were changed according to schematic. I have notice this before in previous projects that components are different from schematic and under chassis. What was the reasoning for this ?
Is this a bad thing to replace components per schematic as per what is in radio.
I have touched around speaker cone and the gasket seem very well glued to speaker frame.
Thanks and have a great day.

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 Post subject: Re: RCA M-46 too much base
PostPosted: May Fri 04, 2012 12:11 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 5528
Location: Annapolis, MD
BlaineA wrote:
Caps were changed according to schematic. I have notice this before in previous projects that components are different from schematic and under chassis. What was the reasoning for this ?
Is this a bad thing to replace components per schematic as per what is in radio.

There could be many reasons for parts not matching the schematic---eg they might have run out of a particular value, or someone figured out an "improvement" and did not update the schematic.

If the schematic and the actual set don't match, then you can go by other similar circuits or good old-fashioned trial and error.

NOTE: We can't see the schematic you linked without being member(s) of radiomuseum--I checked nostalgiaair and it's not there.

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 Post subject: Re: RCA M-46 too much base
PostPosted: May Fri 04, 2012 12:51 pm 
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Joined: Jul Sun 09, 2006 5:18 pm
Posts: 1278
Location: Dandridge, TN
Excessive BASS is also quite common on old radios, since today's music has much more bass content that when the radio was new. For example, in many Zenith table tops, if I press the LOW BASS button on the Radiorgan tone controls, I get excessive speaker cone excursion and distortion at quite low volume levels (the speakers in all cases are perfect - no loose cones etc.) Solution: do not use LOW BASS, or BASS in your case. In my case, it usually happens on classic rock or classic country stations (I am lucky enough to have 4 such AM stations in my area!)

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