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 Post subject: Zenith Solid State...?
PostPosted: May Sun 17, 2015 7:45 am 
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Joined: May Sun 17, 2015 6:52 am
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Good day

My parents have had this Zenith in our home all my life growing up and as I just bought my own new home I wanted it. and as my parents have had it in storage for a few years it really was no issue.

Now even though time hasn't treated the wood badly the one speaker is about half the volume the other one is and the inside is fairly clean which means no bugs or mice have gotten into it while it was in storage and other than dust which a good cleaning will help lol

So here is kinda what i'm trying to figure out.

1) I would like to know the model number of this so i can research how other people have restored these

2) I would like to find an online overview of how they were built inside so i can pull the unit apart and make sure there are no burnt out pieces inside and replace the burnt out light in the one touch sensor as well as make sure i safely pull out the electronics before i resurface the unit.

I know this may pi$$ a few people off but i have 0 use for a record or tape player anymore, so i would like to see if anyone has rebuilt these units with modern head units and speakers. My parents actually want to see want can be done to it to bring it up to date.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 2:30 pm 
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That looks to be a model 966 which was introduced in the 1971 line and was available until 1974.
It will be one of these model numbers... B966, C966, D966 or E966.

It was the top of the line model at the time.

It could be restored, most likely all electrolytic capacitors have degraded to the point they need replaced. Once recapped, it will probably be a solid performer.

I'm not sure where to get service information. I used to have access, but the Zenith shop I worked at is gone, and so is all the service manuals... :cry:

-Steve

P.S. Please, do not go by the amplifier power ratings. This was before ratings were standardized in RMS ratings.
This stereo is probably able to output 15-20 watts RMS per channel.
Maybe 12 watts undistorted.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 2:53 pm 
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Location: Detroit, MI USA
First of all, that was the best stereo console Zenith ever built, although they were quirky and sometimes had their share of service problems. Most consumer stereo consoles have little value and are of no interest to collectors, but this is one of the exceptions. When working properly, it has excellent sound.

Whatever you do, do NOT modify the unit!!!!! Anything you do to it would degrade the sound quality, such as replacing the speakers with different ones. The speakers in consumer stereo consoles like yours were specifically chosen to resonate well with the cabinet and the size of the chamber the speaker is mounted in. It would sound worse if you use different ones and there is no way to compensate for that.

I have been in electronics for many decades as a professional technician, worked on these sets when they were new, and do not understand what you mean by the term "head unit" as that is not a term used in conjunction with consumer electronics.

As Steve pointed out, at this age the unit needs to have the electronics serviced by someone with experience in solid state stereos of that vintage. There are quite a few electrolytic capacitors that should be replaced, and it's likely that's what is causing your low volume issue, although there have been cases where transistors have failed.

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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 3:28 pm 
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Location: Dayton Ohio
I agree with Dennis, please don't modify this stereo.
At least keep things so if you do change something, it could be easily put back to original without anyone knowing the difference.

Unfortunately, I don't ever remember any of these coming in the shop where I worked. I would have loved to know how they perform.

-Steve

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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 5:07 pm 
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Joined: May Sun 17, 2015 6:52 am
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azenithnut wrote:
That looks to be a model 966 which was introduced in the 1971 line and was available until 1974.
It will be one of these model numbers... B966, C966, D966 or E966.

It was the top of the line model at the time.

It could be restored, most likely all electrolytic capacitors have degraded to the point they need replaced. Once recapped, it will probably be a solid performer.

I'm not sure where to get service information. I used to have access, but the Zenith shop I worked at is gone, and so is all the service manuals... :cry:

-Steve

P.S. Please, do not go by the amplifier power ratings. This was before ratings were standardized in RMS ratings.
This stereo is probably able to output 15-20 watts RMS per channel.
Maybe 12 watts undistorted.


I'm not surprised it was the top of the line my parents never did anything cheap when i was a kid, which may explain why i love the look of the unit. Thank you very much for the information, I am have a hard time finding anything online about these units. I'm a computer geek by trade and have played with electronics in one form or another all my life, ripping apart my first computer when i was 5 lol. So I ask this with an interest in doing it. How do I recap the "electrolytic capacitors", is it possible to do from home?



Mr. Detrola wrote:
First of all, that was the best stereo console Zenith ever built, although they were quirky and sometimes had their share of service problems. Most consumer stereo consoles have little value and are of no interest to collectors, but this is one of the exceptions. When working properly, it has excellent sound.

Whatever you do, do NOT modify the unit!!!!! Anything you do to it would degrade the sound quality, such as replacing the speakers with different ones. The speakers in consumer stereo consoles like yours were specifically chosen to resonate well with the cabinet and the size of the chamber the speaker is mounted in. It would sound worse if you use different ones and there is no way to compensate for that.

I have been in electronics for many decades as a professional technician, worked on these sets when they were new, and do not understand what you mean by the term "head unit" as that is not a term used in conjunction with consumer electronics.

As Steve pointed out, at this age the unit needs to have the electronics serviced by someone with experience in solid state stereos of that vintage. There are quite a few electrolytic capacitors that should be replaced, and it's likely that's what is causing your low volume issue, although there have been cases where transistors have failed.


Well i can tell you this much. In the 36 years i've been alive there has never been a service call on this machine and it was more than a solid performer while I was growing up. My parents had a big home and it never failed to fill it with sound. Today however even though my home isn't as large, as long as this unit stays below half, it still sounds good however once i start going up in volume the quality begins to deteriorate rapidly. Replacing the speakers with ones that fit shouldn't be hard, the problem like Steve says is making sure you get ones that are the right amperage for the internal equipment. My first concern for speakers in this case the 15" woofers would be the weight. The magnet on this as you can see is virtually non-existent, where some of the woofers out there today esp of this size will have a significant magnet on them. The Mid/tweet at the top will be no issue.


azenithnut wrote:
I agree with Dennis, please don't modify this stereo.
At least keep things so if you do change something, it could be easily put back to original without anyone knowing the difference.

Unfortunately, I don't ever remember any of these coming in the shop where I worked. I would have loved to know how they perform.

-Steve


I'm trying not to be rude when i say this but the equipment inside is so far out of date its not even worth saving in my opinion. What i would like to do, is use the existing wood frame and build modern equipment into it. A system where I can hook the stereo into my home network or link my smartphone with bluetooth adapters. I know you guys aren't going to like this and i'm sorry, but i want a working modern stereo with the beautiful look that this unit currently provides.

Am i the only one to have proposed this idea?


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 6:43 pm 
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Location: Mpls, Minnesota
You can do as you please but after you are done I really don't think you will find you have improved anything and more than likely have gone backwards in performance. And the value of the unit will be drastically reduced.

Dave


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 7:14 pm 
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Joined: May Sun 17, 2015 6:52 am
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easyrider8 wrote:
You can do as you please but after you are done I really don't think you will find you have improved anything and more than likely have gone backwards in performance. And the value of the unit will be drastically reduced.

Dave



I very possibly may have, but i never intended to sell the unit. so it's value is all intrinsic.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 8:19 pm 
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The amp section appears competent to me from a simple rear view. It's a fairly beefy power transformer and the TO3 outputs are generally capable of up to 50 watts, but 25 watts RMS may be more realistic given the simple heatsinks. As you noted, that's easily enough to fill the room.

The speakers are a weak link. While you could simply remove and replace them, the open-back cabinet and generally light construction will work against a modern long-throw woofer with a foam or other flexible surround. Those speakers designed for an air-tight enclosure. In an open-backed cabinet, the cone will exceed normal travel with resulting distortion and the voicecoil may be driven into bottoming out. The cabinet will likely have buzzes or resonances at certain bass frequencies. All that would be readily audible and hardly musical. If you want to upgrade the speakers, you would need to look for a woofer with a relatively stiff suspension, such as a guitar speaker or perhaps some vintage driver or similar modern version. That or the interior space for the speakers would need to be converted to a stiffer and better sealed enclosure to accommodate a foam-edged driver. You'd still need to address potential issues with the horn tweeter and very simple crossover. You won't be able to readily alter the speaker opening, though an adapter panel to mount a different size tweeter is possible.

The receiver seems to be about 17 inches wide. A more modern receiver might be found to fit into the opening, but again there are issues. Modern equipment is not designed to be hung from the front panel. You would need to provide some sort of secure method of supporting its weight. All the cable connections will be pointing downwards deep into the cabinet's interior, making hookups frustrating.

You would need to make a new panel to cover the gap, as the original receiver is quite tall. If you need to increase the opening for a wider receiver, you'd have to make those cuts inside the exisitng cabinet. It might be attached with screws, but is likely to be well-glued in place. Unless you're a careful woodworker with proper tools, it would be a messy job and hard to make it look nice. All that is possible, but still a tall order.

The smoothest "upgrade" would be to add a pair of external speakers, once you have the weak channel sorted out.

Possibly you can switch the wires to the speakers to see if the weak sound stays on the same speaker or moves to other side. If it stays on the same side, you have a bad speaker issue. If the weak chanll is now on the opposite side, it's in the electronics.

Sometimes this can be due to a dirty switch or control. Work them all and listen for any changes.

I see this has a 1/4" headphone jack. You will likely need an adapter to fit the more modern 1/8" jack. You can listen to headphones to see if the problem is there or just in the speakers.

The electronics look open and accessible, once the components are removed, that is!

Due to the various issues I point out, besides its status as a TOTL Zenith stereo console worth saving in its own right, it's probably best to try to repair it rather than attempt an upgrade. If you do "gut" it, save the old parts with all their wires and plugs and cables. Someone can probably put them to good use. If possible make your cabinet alterations reversible if possible so the next owner could potentially revert it to original.

-Ed


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Sun 17, 2015 10:43 pm 
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Posts: 1652
The configuration of the speaker system is such that it will be quite efficient, and therefore need very little power to play loud. I haven't found these console amplifiers to ever have very much power, and this one probably would be good for maybe 20 - 30 watts per channel. That's plenty to raise the roof with the speaker system that's being used. The size of the magnet is in no way an indicator of performance. I also wouldn't replace them, because they're perfectly suited for the kind of application they are in. These woofers use alnico slugs in a boxed magnetic circuit. There will be a small pole piece on the top of the magnet. It is likely that the magnetic circuit is "underhung", meaning that the voice coil length is shorter than the the length of the magnetic gap. This makes the moving system light and all the magnetic flux is concentrated into the coil at all times. Because the woofer is large, it doesn't have to move very much, which is good, because its linear travel will be quite short by design. I'd estimate sensitivity somewhere around 95dB- 1watt, 1 meter. That's a lot more than you find in most component speakers. The tradeoff is that the open baffle design isn't very good in deep bass performance, and the high Q woofer will be a bit mushy sounding. But the "warm and fuzzy" sound is what these consoles are known for.

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 Post subject: Re: Zenith Solid State...?
PostPosted: May Mon 18, 2015 12:27 am 
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Location: Sunnyvale CA
talamakara wrote:
easyrider8 wrote:
You can do as you please but after you are done I really don't think you will find you have improved anything and more than likely have gone backwards in performance. And the value of the unit will be drastically reduced.

Dave



I very possibly may have, but i never intended to sell the unit. so it's value is all intrinsic.


It would be rather simple to add an auxiliary input to run an external source like an MP3 player if you find the schematic, and many of us might be able to figure out where it goes just from looking at it.

If you want a modern stereo setup, I would recommend a modern stereo setup, and not to spend an inordinate amount of time trying to bring this one up to standards.n particular, as noted above by others, you *will not* be able to replace the speaker drivers in the same cabinet and have good results. No modern drivers are designed or intended to be used in an open-back cabinet. To get any sort of good modern speaker, you would need to take an existing good component speaker, crossover, enclosure, remove the old drivers, and put the complete speaker inside.

Then I think you will find that the amplifier is not up to driving it at decent levels without distortion. The "320W" claim is the sort of thing that the IHF (institute of high fidelity) testing regime was invented for, almost literally. It really is about 12W or so as noted, and will very likely be far less than that into a modern hi-fi speaker. And modern speakers are pretty inefficient, so you now have about 6-8 watts trying to drive a 86 db/watt speaker with a huge and varying impedance mismatch.

You will be better off leaving the speakers alone, and just refurbishing the amp and adding an external line input (which probably should go where the tape deck output goes to the amplifier). Anything beyond that, you would be much better off just buying a component stereo system.

Brett


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Mon 18, 2015 12:39 am 
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Thank you very much for the great information. I'm going to do a bit more research on this before i rip it apart. But in the end i think that will be my winter project.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Mon 18, 2015 4:57 am 
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Location: Minnesota
I guess I have a hard time figuring out the logic. There are adapters you can make to allow you to use MP3, or a Bluetooth to FM modulators are available. Yet you seem determined to chop it up.

It is yours, do as you wish. But I've done it and others that have already posted have done it, you are not going to improve anything. Every component in that set was designed to work together.

I'm not a real console lover. Only the really good ones and that one is a really good one. Hate to see it wrecked for experimentation.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Mon 18, 2015 6:31 pm 
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It would be easy to adapt an mp3 player into it without modernizing anything. But it has zero collector value anyway so do whatever you want. Have fun with it.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Mon 18, 2015 8:33 pm 
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Location: Minnesota
There is a small, but growing quickly, group of console collectors around. Many consoles have zero value, but this is not one of them. It was one of the very best made that year and should current trends continue, the value is going to go up dramatically. Look what has happened to Magnavox units lately, tube and solid state. And not all of them are being gutted.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Mon 18, 2015 8:58 pm 
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Location: Charleston, W.Va.
+1 to ggregg's last post. There is indeed a rapidly growing interest in consoles. Most of that interest is in tubed consoles from the late-50's-early 60's, but also high-quality SS consoles such as this Zenith.

In my small radio/audio repair business, in the past most of my work was on antique radios. That has shifted very rapidly in recent years. Now most of my work is on vintage tubed audio gear, both consoles and component systems. And most of my work is now done for younger customers who have either inherited the gear or bought it at yard sales, flea markets, etc. I attribute much of this to renewed interest in vinyl LP among younger folks.

To talamakara:
Thanks for your post and welcome to the ARF forum!

Many here have advised you not to "hack" or "experiment" on your nice Zenith console, and I agree with them. But lest you think that the advice you have received here is from "old fogeys" whose only interest is in "antique" or "vintage" gear, I would encourage you to check out several of the online forums populated by "audiophiles", particularly http://www.audioasylum.com. I believe you will find that they will offer you the same advice regarding your Zenith console that you have received here in the ARF.

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 Post subject: Re: Zenith Solid State...?
PostPosted: May Tue 19, 2015 2:04 am 
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It may be a great performer, but its still an ugly cheaply made 70's console that would be hard to give away and most likely end up on the side of the road before the seller ran out of patience waiting for that 1% niche that might be interested in it. It just doesn't have the classic status of a 50's or mid 60's instrument. Ebay has artificially driven up prices on just about all electronics, but in most cases it's because of greed, not value. I honestly wouldn't pay a dime for it. And personally I wouldn't upgrade it either, because there is no need to. I'd just re-cap it, add a mp3 input if there is no aux, and seal up those speaker enclosures like the ad says they are. No offense to talamakara at all. It's worth a million to him no matter what he does with it, because its an heirloom.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Tue 19, 2015 4:31 am 
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Location: Minnesota
Oh come on Metzman, tell us how you really feel........ :mrgreen:

Your wrong BTW. I've seen the same thing Poston has, and I'm not a console lover by any means. I do work one day a week in an electronics/music shop as I have since 1993. Console repair and phono repair in general is up dramatically.

I sold all the ones I had three or four years ago. They were easy to sell and I made decent money on all of them, of course they were all in good working condition.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Tue 19, 2015 5:03 am 
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Of course.... I'm always wrong. But really? I would chop that sum-bich up and throw it in the fire pit. Take the innards and sell 'em on ebay and make a fortune :roll: . Then take those astronomical profits and put them toward an early sixties unmolested Pilot tube console with an sa232 amp. I just saw one on Craigslist for $900.


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Tue 19, 2015 5:56 am 
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@Poston Drake

The other poster who commented on its intrinsic value to me is right on the fact that it could have a million dollar value and i probably.. (well a million maybe ;)...) wouldn't sell it. However i did come on here to ask for advice and no matter how much i would like to replace the internals with high end equipment, i have read what you guys have said and i'm not just going to cut it all up without having done all my research, and the information from you guys has been in-valuable and i do thank you.

No i don't think you are "old fogeys", I'm just a computer geek who has built many many computers from ground up and i would like to keep this thing working for a few years to come. But also being a computer geek I don't see the point in keeping the old tubes and capacitors and sorry record player.

But before i hack into it at this point, i may not do it, i'm going to re-read everything you guys have said, but i will eventually need to trace out why one speaker is quieter than the other. I will start by using my old headphones and see if they fit into that jack. after that if its just speakers i will probably just replace them, if its not, well i don't know yet. But i promise, what you have typed has not fallen on unseeing eyes.

ohh and btw, the back cover isn't missing, i just took it off to take pictures of the speaker


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 Post subject: Re: Zenith Solid State...?
PostPosted: May Tue 19, 2015 6:43 am 
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Posts: 12549
Location: Mpls, Minnesota
A weak channel is seldom caused by a defective speaker. Most likely it has some bad electrolytics, most of them are probably bad by now and all will need replacing. If operated in this condition you chance damaging transistors and the power transformer. If you were to restore this unit I think you will be surprised by the sound it is capable of producing.

Dave


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