Project Thread: Let's take this '60s retro system to a whole new level!

[DangerBoy]

This is a 1960s Zenith Z565 Moderne Record Player and Circle of Sound speaker system that I just bought. Below are pictures of the actual system that I purchased.

The system wasn't working when I got it because the internal fuse was blown. The seller told me he accidentally blew the fuse while doing some tinkering on the unit but prior to that it was working and could play records but there were problems with the auto-return system. Those issues are being discussed in this thread:

http://audiokarma.org/forums/index....t-probable-cause-s-of-this-tt-problem.792759/

I haven't decided yet what my plans are for this system other than I do intend to resell it and try to make a little profit on it. I want to make it something very cool and desirable for hipsters to own.

There are a number of ways I can go with this system. Here's what I'm thinking are my basic options: If anyone would like to suggest other options, I'd be glad to hear them:

Option 1 would be to simply recap it, get everything including the mechanicals working 100% and resell it. I could do some upgrades to the speakers as part of this option. The discussion on the speaker upgrades/modifications is going on here:

http://audiokarma.org/forums/index....-these-vintage-circle-of-sound-babies.792951/

Option 2 is doing everything in Option 1 and then also installing a Raspberry Pi Media streamer system inside the unit so not only will it play records and look very retro and cool, it can also play digital music streamed from a network share or Internet source via wifi and mobile devices via Bluetooth or Airplay. The media streamer system would be remotely controlled from a smart phone or tablet and would be tied into the auxilliary input side of the built-in amplifier. Upgrading the speakers would definitely be on the plate for this option.

Option 3 would be adding the Raspberry Pi streaming system and doing the speaker upgrades in Option 2 but would also entail doing away with the built-in amplifier entirely and replacing it with a modern solid state amplifier inside the chassis. This would likely improve the sound and reliability quite a bit but would render most of the sound control knobs useless and likely add a few layers of complexity that I haven't even conceived of yet.

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[DangerBoy]

I would like the first part of this discussion to be about the various options I've put forward, the pros and cons of each, how I could actually go about completing those options, what technical issues I'm likely to run into with the various options and also what other option ideas people want to suggest. I'd also like to hear from people who've restored and/or tweaked these systems to find out what they did and how it turned out. I've created a photo gallery for this project that other AKrs can add to. I think having a dedicated gallery showing what I and others have done with these systems could be very useful for people in the future.

Once the plan for this project has been decided, I would like the thread to then document the steps of implementing that plan and then finally to documenting the results. That way, in the future. people will be able to visit this thread, read about the options that were considered for restoring, upgrading and modifying this system, how the project was completed and what problems were encountered along the way and then finally how it all turned out and what it sounded like at the end.

I look forward to this and I hope other AKrs will too.

Let the discussion begin...

 

[DangerBoy]

Just to get things started, for Option 2, I was considering using a Raspberry Pi 3 with a Hifiberry Dac+ Pro board (https://www.hifiberry.com/shop/boards/hifiberry-dac-pro/) for the music streamer. Also thinking about using Rune Audio's (http://www.runeaudio.com/) system for controlling it from any mobile device. The streamer analog output would be tied into the Z565's Aux inputs.

For Option 3, I was considering using a Raspberry Pi 3 with a Hifiberry Amp 2 board (https://www.hifiberry.com/shop/boards/hifiberry-amp2/). Going this route would enable me to remove the old amplifier section altogether but I might need to add a Phono stage amp for the turntable. If that's the case, I was wondering if something like this Very Simple Phono Stage amp board and direct the its output to the Hifiberry Amp 2 board.

Going the option 3 route would then eliminate the functional usefulness of the various control knobs on the record player which might take away from some of its charm. It would, however, probably render a better overall sounding system than simply recapping the antiquated 1960s amplifier in this record player. On the other hand, there may be only so much I can do to improve the sound quality of the Circle of Sound speakers and they may be the limiting factor in either case so it might be that going Option 3 wouldn't make any appreciable difference to the overall sound quality. What are people's thoughts here?

I have to admit right here I don't know a lot about Raspberry Pis so I'm going to need a lot of help from others to get myself up to the point where I can actually accomplish what I'm putting forward in either of these options.

 

[bobins08]

Not an area of expertise for me.

 

[avionic]

Option 4...

 

[soundmotor]

I've had that exact system. I could never get the TT working properly as the grease had turned into glue and virtually nothing operated. It would have required an extensive teardown & refurb as well as new stylus just to get a marginal evaluation. I did listen to the speakers and sold everything as is shortly after. They were crap.

That said, the speakers are a real limit to how good the system will sound regardless of the electronics. At the minimum I would look for a better full-range driver to stuff the enclosures with. It's been ~10 years but what I do recall was how flat they were. This should be addressed.

My recollection on the TT was that is was close enough to standard size of the era that a working BSR, Dual, or Elac could be dropped in if that one is too tough to get going. I don't recall the cartridge set-up but think you will be limited to stylus replacement or a very narrow range of cartridges that fit the shell. If you went to a different TT instead you'd be able to fit a standard cartridge there. (I could be complete off on the headshell, I just don't recall what there was under there.)

I like Option 3 for condensed packaging but agree on loss of functionality with the controls. I'd probably opt for one of the Chinese class-d combo amp/preamps with bluetooth built in. Then extend the pot wiring and put new pots & switching in place of the existing controls. For the phono stage add any of the self-contained modules underneath and call it a day. You could likely keep the costs under $200 with careful shopping and that includes the TT, phono stage, plus the rest.

 

[gadget73]

me being me, I'd go for option 1. Maybe go for #2 if option 1 works out well.

 

[electronjohn]

Pop in a better TT (even a cheap BSR w/mag cart would be an improvement) and bury a tiny phono pre inside the unit. I'm also with those who advocate upgrading the internals in those speakers. In the end you'll end up with a pretty good compact system.

 

[gadget73]

A beezer would probably be a lateral move honestly. The VM 1200 isn't amazing but not completely horrid either. There is probably a mounting adapter gizmo that will let it take a regular 1/2" cartridge, or hot glue does exist I have a MicroTouch 2G here, which is a couple years older in another Zenith. It works fine. The cartridge is on a goofy spring suspended thing, and it does honestly run at 2 grams. I don't have any special love for VM changers but they do actually work OK when serviced. I'd much rather a Garrard SL-65 though.

 

[HypnoToad]

I'd much rather a Garrard SL-65 though.

The console stereo my dad bought in 1970 had a Garrard SL-65 with a flip over stylus ceramic cart, we thought it was state of the art, we still have some of the records played on it, I won't go into what they sound like now.

 

[gadget73]

Thats more the fault of the cartridge than the machine. The SL-65 can be run with a decent magnetic cartridge, at which point its no worse than a lot of other things. Its the best small format changer that Garrard made though, and it should fit into the same space as a VM 1200. I'd definitely take that over a BSR, but I really do not care for BSR machines at all.

The AT-60 is basically identical but has a slightly lesser but still good motor. Some others in that family had a crappy 2 pole motor that vibrates something awful, and you can hear a steady hum through the speakers because of it. The one in the KLH 24 I had was one of those. Records had a 120 hz hum, and you could feel the vibration if you touched the top of the deck. I get none of that on my AT6 or the AT60 I used to have. 4 pole motor vs 2 pole. The SL series has I think an 8 or 12 pole so it should be even smoother.

 

[DangerBoy]

Okay, let's start planning what we're going to do.

I don't think it'll cost that much to try Option 2 first and that option has the advantage of keeping all of the adjustment knobs fully functional. If the thing still sounds like crap or can't power the replacement coax drivers, I'll switch to Option 3 and re-amp.

First lets look at all the insides of the thing in a macro view:

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If we look along the right side where the various tone and volume controls are. It can be seen that there's quite a lot of brown blob non-polar coupling caps there. There's also some transistors and lots of resistors. Any reason I should target the coupling caps and replace them as a matter of course or should I just leave them alone? Below is a close-up of some of the coupling caps.

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What about the transistors? Below is a diagram showing what transistors are being used. I believe there are modern day replacements available for them.

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Below are two views of the PSU and amplifier section in two different machines. A number of electrolytic caps can be seen there.

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I've outlined the caps I'm thinking I should definitely target for replacement. Is there anything else in this section I should also target?

The fuse is blown on the unit I have so rather than replace it with one of those soldered in glass fuses that are a hassle to change out, I'm wiring in an inline glass fuse holder. I can tape the spare fuses inside the chassis so they're immediately handy if the fuse ever gets blown again. The PO blew the fuse when he was tinkering. Hopefully, the fuse did its job and nothing was damaged.

 

[OMGCat!]

The coupling caps should still be good but if in doubt give them a check. I'd start with electrolytics and go from there (the ones you have circled are the ones I'd replace for sure). If the transistors are good then no real reason to mess with them.
If you do decide to go Class D you could leave the original pre in place and feed the new amp module off of where the amp gets it's signal from already. That way you could keep all of the original controls. I did this on a friends dead and already butchered late 60's Panasonic and it worked fine. You could then buy a separate BT module and install it somewhere in there which you can do with either amp.

I haven't messed with many changers but the few I have just needed cleaning, lubrication and new idler tires and then they worked acceptably well.
Speakers are something I buy already made so no input there.

 

[DangerBoy]

How would I check those coupling caps? With an ESR meter? I don't have one of those. I also don't know how to check the transistors but getting new ones and replacing them isn't too expensive or difficult...

I was told that other than the problems with the tonearm auto-return system which is most likely a cleaning and lubrication issue, the unit was working until the fuse got blown. Assuming that's the case, the coupling caps and transistors are likely okay but how reliable are they at that age? There aren't that many transistors to replace so I don't mind doing that just to be safe but replacing all those coupling caps as a matter of course would be a real chore...

> If you do decide to go Class D you could leave the original pre in place and feed the new amp module off of where the amp gets it's signal from already.

Okay, here's where it becomes obvious (if it hasn't been so already) that my knowledge of electronics is rather limited. Where is the pre-amp part of this? I know there has to be one because of the turntable but I don't know how to identify it vs the main amp and PSU. When I look at the guts of this thing I just see a whole mess of passive components, most of which I can identify but I don't really know what the various sections of the electronics are doing. Obviously, all of the components attached to the bass and treble knobs are conditioning the sound, the components clustered around the balance and volume knobs are controlling the gain in the various sides of the signal. I assume that happens in the amp stage and not the pre-amp. Correct?

Forgive me if I ask a lot of dumb questions but I'm not an EE or electronics tech. I'm an environmental engineer with geological engineering education. I'm eager to learn about this stuff so the only way I can do that is to ask all sorts of questions. That's how I've managed to learn what I have so far which I'm beginning to see is not that much.

 

[OMGCat!]

You can get an LCR meter super cheap off of eBay but those poly caps rarely if ever go bad.
For the transistors there would be no gain at all to be had by changing good for good so I would leave them be. Transistors don't typically wear out unless they are in higher stress situations.
A schematic would be able to tell you exactly what you need. From looking at the pictures the input of the amp is likely that coax that's coming from the knob area going into the main amp box.

I'd fix the fuse and listen to it a little and see what you think before worrying about anything. It's good to get a baseline of functionality before digging in so if there's a problem later you will know if it already existed of if you introduced it.

No worries on all of the questions. I don't do this for a living and only have a year of electronics under my belt from a bunch of years ago.
Reading here and asking questions is a great way to learn.

 

[DangerBoy]

Are you able to tell what the various electrolytic caps are doing in the amp section? I'm wondering if replacing any that are along the signal path near the output stage with a little better quality audio-grade caps might have a positive effect on sound quality. I wouldn't spend a whole lot of money on them because this whole thing is gonna be mid-fi at best but I'm thinking maybe the three smaller ones near the output transformers might be potential candidates for this.

 

[gadget73]

value and leakage is the ideal test but those are a film type that usually will be around when nothing remains but cockroaches and Twinkees.

Without a schematic the electrolytics are a little harder to guage. They may be power supply filtering, but SS amps often used them for signal coupling too. Low impedance needs a high value cap in order to not filter out the lows. Guessing this is a cap coupled amp, so there is probably a large cap on each channel between the amp and the speaker for DC blocking. Those look like Callins caps, and those are not particularly awesome.

 

[Ohighway]

Option 2.