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  #16  
Old 04-18-2014, 12:50 PM
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davet753 davet753 is offline
David Thomas
 
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Location: Knoxville, TN
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Thought someone might like a pic
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  #17  
Old 04-19-2014, 02:07 PM
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davet753 davet753 is offline
David Thomas
 
Join Date: Mar 2013
Location: Knoxville, TN
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It's fixed!!

After thinking about it for a while, I decided I really ought to replace those original 6BQ5 audio output tubes. I had read that the 6BQ5's are commonly used in guitar amps, so I made a phone call to a local guitar shop. They told me they had 4 of them in stock, for $7 each. I ran on over there to get them ($7 a piece is the best price I've seen on them). Three of the tubes are new production "Mesa" brand tubes and one is a NOS General Electric tube.

I knew when I powered it up the first time I made a wise decision. The volume control (which was set to almost the center position before) had to be cranked down. The sound is twice as loud and twice as clear as it was before. I had to turn the bass control down quite a bit to keep it at a comfortable level (it has been set wide open with the original tubes). With the set of 4 new output tubes, I had no problem at all adjusting the current balance control to exactly zero volts.

I flipped the chassis over, and lo and behold....the B+ was down 12 volts from what it had been before. This is much more in line with what I felt was a comfortable increase considering today's higher line voltages. I also noticed that after being turned on for an hour, the power transformer was still relatively cool to the touch (it was running pretty warm with the old tubes).

I am thrilled with how well this old girl is performing now!
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  #18  
Old 04-19-2014, 11:44 PM
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Electronic M Electronic M is offline
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Location: Pewaukee/Delafield Wi
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Nice work, and a nice looking set.
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Zenith: The quality stays in EVEN after the name falls off!
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  #19  
Old 04-20-2014, 05:21 PM
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davet753 davet753 is offline
David Thomas
 
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Location: Knoxville, TN
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I have to admit, this unit sounds exceptional. The bass is very punchy, without the "boominess" that my Magnavox solid state consoles have. The horn tweeters have rather short horns, and produce less mid-range sound than some exponential horns I have heard.

The tuner (like most top-end Zenith's of that era) is fantastic! With the built-in antenna, it brings in the weaker FM stations that most radios leave out. Even the AM bank is quiet and sensitive. As odd as it sounds, the FM receiver is not stereo....the record changer and tape inputs are stereo. This was Zeniths best in 1961, and in 1962 the replacement chassis for mine had FM stereo. I suppose the engineering department figured there weren't enough FM stations broadcasting in stereo in 1961 to make it worthwhile to add that extra circuitry. Unlike the Magnavox sets of that era, no provision was made for adding a stereo multiplex decoder chassis to the Zenith. The owners manual just mentions the option of adding an FM stereo receiver through the tape input jacks.

Now, I've just got to get the record changer back in order. The motor was froze, but I took it apart and cleaned it up and she's working again. When I turn it on, the record drops, the tone arm starts to move over, and then it comes back to the rest and turns itself off. The record changer is a VM (Voice of Music) built machine, and I'm really not that impressed with it. As I told someone else, I am tempted to find a later model Zenith 2G record changer for this stereo. I would hate, however, to loose the cool "Cobra-Matic" tone arm
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  #20  
Old 04-20-2014, 08:27 PM
old_coot88 old_coot88 is offline
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With overly-high line voltage, I would want to watch the output tubes carefully in a darkened room to see that they're not red plating, specially on loud passages.
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