Author Topic: Multiplex adapter came for my 'Imperial, doesn't work well... suggestions please  (Read 1683 times)

lesdab

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Hi all,
Well I have read Larry's thread from start to finish and it has been very helpful. Thanks for it! I am actually wondering if I bought the wrong model multiplex adapter. I would like to know the model number of ones belonging to you all.
I ordered a 7002-00 multiplex adapter off ebay and it arrived today. Of course the first thing I did was hook it up. It works but the sound is weak and staticy on FM multiplex. The sound is powerful and clear on FM or FM afc. I tested the 12AT7 and the 6EA8 tubes. They are strong. I even substituted new tubes with no improvement.
I replaced the white .22 capacitor and no improvement. I will go buy the 30mfd electrolytic tomorrow and replace it but the electrolytic couldn't cause this problem could it? I too have those 5 brown caps with the unfamiliar markings mentioned by Larry in his thread. I did clean the 2 gain pots on it. They were set in the middle when it arrived and I now have the all the way up to get less than decent volume.
In the installation instructions for adapter model KO 597B (looks identical to 7002-00) it says to plug the red rca cable into "sub" on back of tuner but I see Larry's is plugged into "main". I have tried both and sub is a bit louder.
Any advice will be much appreciated.
Thanks,
Les in Redding, Ca.

Larry H

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There are three electrolytics in there that should be replaced, two of them were 4.7 mfd. 50 volts as I recall.  Believe the other was a 33 mfd. 450 volt, but I might be wrong on that one.  As I recall, mine also only had one wax cap in it. (the white cap).  My multiplex unit works extremely well.
--Larry

lesdab

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I changed the 2 mfd and the 4 mfd caps and it works well now! Going to change the 30 mfd in a few minutes. Thanks!

lesdab

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Multiplex adapter is all recapped, installed upside down under the tuner and works perfectly! Now all I have to do is take the amp and tuner out and recap them.

Larry H

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Take the amp out first to get it out of your way.  Then, remove the changer.  Remove the knobs from the front of the set.  Forgetting to do so could cause the plastic face plate to crack.  Then, remove the tuner and MPX adapter, which are mounted together by the same screws.

BTW, your power amp is installed backwards in this picture.
--Larry

amglow

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I don't know.  Mine is oriented in the same way, as seen in the attached image.  That's 53 years of undisturbed dust accumulation you see on the amp, after I removed the back cover.  I don't think it was ever serviced.  Looks all original, including the Magnavox labeled tubes.  Maybe it just depended on who installed the amp during initial assembly?
Paul

Larry H

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The amp should be installed the way mine is, since there are three wires for the Channel 2 external speaker that come off the back of the amp and attach to the back cover.  The tubes are also easier to access with the amp installed the way mine is.  Here's a picture David made of mine before I got it:
--Larry