Author Topic: 1964 Zenith console with drop-in tuner  (Read 3046 times)

Motorola Minion

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1964 Zenith console with drop-in tuner
« on: May 26, 2016, 11:09:55 AM »
The local Habitat ReStore is where I take minimally-functional consoles which still has value for someone. A good example is my 1966 Silvertone SS console that had needs (germanium transistors and unobtanium changer parts) not worth the time of a collector that has more interesting stuff lined up to restore.

This time a treasure was found. I saw it last week for $50 and figured if it lasted a week, that was a sign to bring it home.  This Zenith MT1971 in a very nice walnut cabinet with twist-on legs and six speakers inside. Not a TOTL tubed console but one with a single-ended 6BQ5 stereo amp with bass-boost switch and an MLT15 stereo tuner with its own power supply.

The record changer was a V-M of course but had no markings on it like most Zenith's do. The cartridge looks like an Electro-voice 150, similar to what is used on Magnavox Micromatics of the same age.

I was able to offload it into my basement studio and its next to a 1959 Zenith from an earlier post. Ill post some pictures next.
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Dave

Motorola Minion

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Re: 1964 Zenith console with drop-in tuner
« Reply #1 on: May 27, 2016, 03:59:01 PM »
The changer that came in this Zenith has an EV186 cartridge, which looks like an E-V 150 but has an adjusting screw at one corner ??? - is this an anti-skate or azimuth adjustment?

The changer is dated 6507, is in above average condition and plays records well but I'm swapping it with the 1970 Zenith Super 2G-branded V-M that was in my 1959 console.

The 2G changer will be closer to the Zenith-branded changer what the 1964 came with originally. One thing the 2G hates is very worn records, more so than the generic V-M with the heavier tracking EV cart.


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hermitcrab

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Re: 1964 Zenith console with drop-in tuner
« Reply #2 on: June 07, 2016, 08:03:39 PM »
Everyone seems to love the 2 gram changer, to me it is too sensitive, just shutting the console cover while playing or walking near the set will cause the stylus to skip, the springs are so sensitive on the changer, that after the record drops the tone arm will skip due to the springs still moving from the changer action...
Elton

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Re: 1964 Zenith console with drop-in tuner
« Reply #3 on: June 08, 2016, 12:58:34 PM »
Everyone seems to love the 2 gram changer, to me it is too sensitive, just shutting the console cover while playing or walking near the set will cause the stylus to skip, the springs are so sensitive on the changer, that after the record drops the tone arm will skip due to the springs still moving from the changer action...

That is exactly what happens. Even on new vinyl :( Most V-M changers have foam cubes stuffed inside the springs to dampen such action. I just replaced the dried out ones with cubes of foam "bug-strip" (sold for window AC unit installs) and am hoping for improvement. Since the 2g is now in my 1964 console of this post, I need to work on its amp before I test it. First thing to go is that 4 amp fuse - WTF was Zenith thinking there. Schematic claims the power transformer draws 110 watts. I'm thinking 2 amp fast or 1.25 amp slow fuse here. That is just to get started. Ill do a separate post in Repairs/Tube consoles.

Zeniths of all vintages have an occasional nasty habit of blowing up transformers 
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Larry H

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Re: 1964 Zenith console with drop-in tuner
« Reply #4 on: June 08, 2016, 01:01:53 PM »
It is earlier than 1964 if it has tubes.  By then everything was solid state.
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Ken Doyle

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Re: 1964 Zenith console with drop-in tuner
« Reply #5 on: June 09, 2016, 06:36:44 PM »
Zenith still made some all-tube stereo consoles through the 1965 model year.  They were also among the last to switch to circuit boards.

hermitcrab

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Re: 1964 Zenith console with drop-in tuner
« Reply #6 on: June 10, 2016, 08:41:35 PM »
yes get rid of that 4 amp fuse.... I was told since both chassis, tuner and power amp... not to mention the turntable, all go thru the main transformer hence the 4 amp fuse, but it is too high, my transformer failed... the primary winding fried and fuse did not blow...
Elton

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Re: 1964 Zenith console with drop-in tuner
« Reply #7 on: October 26, 2017, 03:10:21 PM »
I bought some radial speakers from HiFiFun and they should be here soon. Thanks Larry!

I moved this Zenith to the front of the line, equal in priority to the paying jobs of course. The 2g changer and and another V-M are on my bench right now and I hope I'm done buying parts. But you never know how those idler wheels will turn out. I have a new one that I'm hoping to use on the customer's unit so I get paid for it. My unit also needs the stylus selector knob, a commonly lost item on Zenith 2g's

The Single-ended 6BQ5 amp should be able to drive these along with the 6 in the cabinet. The console has the plugs for them, how lucky to actually find a pair, that match woods too!
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Dave

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Re: 1964 Zenith console w-radial speakers
« Reply #8 on: November 06, 2017, 09:56:02 AM »
What I found with these MR105 speakers is that the plug is different than both this tubed Zenith and a 1966 Color TV SS Stereophonic console having radial speaker plugs. The manual of this 1964 console refers to radial speaker model KR102 According to my Zenith factory manual, the KR102 has 6x9 drivers but a 3" cone tweet instead of the short horn in the MR105.

Both have five pins but the arrangement is different. After looking at the pin-out, I can adapt these to an older "shorting plug", and both my units have those.
The selector switch is the other odd thing, if you select radials to work in tandem with the console's internal speakers, or not at all,  both the inductor and non-polarized capacitors are removed from the overall circuit. The in between function is to run the radial speakers only, while disconnecting the console's internal speakers.

It seems an undesirable situation is to route the amp's left and right outputs from the receptacles, through the 25+ foot cables to that switch on each radial speaker and then back to the console's internal speakers. The "shorting" plug will remain that but act only as a tap for connecting the extension speakers in parallel. That half-ohm loss in 50 feet of stranded #18 conductor has to be a factor.

I'm sure the MR105 are from a later unit, and I have not yet checked receptacles on my 1969 model Z966, with the large separate amp chassis. Unfortunately I don't have Zenith manual on the newer equipment.
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Dave

Motorola Minion

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Re: 1964 Zenith console with drop-in tuner
« Reply #9 on: November 17, 2017, 01:28:54 PM »
I have changed the plug and am ready to try the extension speakers on the solid state Zenith combo. The tube console needs its caps changed first.
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Dave

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Re: 1964 Zenith console with drop-in tuner
« Reply #10 on: December 05, 2017, 03:25:09 PM »
The remainder of the odd-ball caps came from Justradios. A bunch of 220/470pf caps in the amp have cracks in them, weird. A non-polar electrolytic is used in the tuner and I ran out of Y2 safety caps.
I plan to put a grounded cord on this console to reduce noise and make sure the AUX cord I add does not become a tad hot via the chassis ground. Besides that, the cord looks pretty crummy.

I hope to test the radial speakers on this first, after moving it into the living room for break-in use. The SS console is serving as a padded tool-table, hard to lift lid.
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Dave

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Re: 1964 Zenith console with drop-in tuner
« Reply #11 on: December 15, 2017, 01:48:44 PM »
I have finished the tuner. This one has its own power transformer, which has a half-wave selenium rectifier (blue square cards) and 12 volt center tapped tube heater winding.

The selenium is replaced it with a 1N4005 silicon rectifier. The three power supply capacitors fit neatly onto a terminal strip, nutted onto the end of the selenium stack. This power supply is easy compared to the amp chassis.

Only two other electrolytic capacitors, a 10mf in the ratio detector and a non-polar in the audio path to the on-board mpx decoder, were replaced with new. Only five paper caps replaced with film caps were needed. Selector switches and tube sockets were cleaned with de-0xit D5. 



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Dave

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Re: 1964 Zenith console with drop-in tuner
« Reply #12 on: January 26, 2018, 04:19:09 PM »
The 4L21 amplifier chassis is a dream to work on as my 4th Zenith tube amp restore.

I actually replaced most of ceramic caps as well. Some appeared to have cracks in them, the dark red ones with zenith's yellow numbers on them.

The best part about this chassis is the amount of room you have to put new capacitors in and use terminal strips for the OEM Zenith look.

I will post some pictures of the recapping effort but it is my best effort to date.

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Dave

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Re: 1964 Zenith console with drop-in tuner
« Reply #13 on: May 17, 2018, 01:56:45 PM »
This tuner and amp is almost ready to pack up and install. I have been using it for a few weeks now and just a few quirks remain. After figuring out my wiring mistake on the amp, I still have insufficient high frequency response. The circuit for treble looks like the simple "timbre" control on a Magnavox SS receiver. Just a 500K pot in series with a .01 mf cap across the line. Maybe Ill change that to a .0082 or .0068, but will use the decade box to see what value sounds best. Only after I verify the 3" cone tweets are OK*

*I may need to replace some speakers and then fully enclose them, just like another forum member did with an RCA, very easy the way the cabinet is built.

Pictures next time, the record changer is the last big task.
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Dave

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Re: 1964 Zenith console with drop-in tuner
« Reply #14 on: May 21, 2018, 11:59:15 AM »
The tuner was acting pretty weird on FM, as if there was a muting or quieting function, which there is not. I swapped the 6JK8 and no improvement. There is only an FM and FM stereo selector button, and reception on both was poor. I had an alligator clip and 3 foot jumper on the tuner's antenna terminal but only a few stations came through. Normally this is sufficient for local reception on most tuners I see.

I reconnected the cabinet antenna brown twin-lead and it received much better, almost normal and with nothing connected to the screws.  ???. Then I realized this tuner must have been set up to work with that exact length of twin-lead to the screw terminals.



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Dave