Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Dec Thu 12, 2019 7:29 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 19 posts ] 
Author Message
 Post subject: Zenith MH2685 Console Repair
PostPosted: May Sun 19, 2019 10:53 am 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
Hello

I have this lovely Zenith console MH2685 which has been imported into the UK, I have repaired 8 european consoles here in the UK and many other british radio sets but never worked on anything from the US especially a US console as they are pretty rare here in the UK. Its had an auto transformer fitted to bring the voltage down and had a new motor assembly fitted to adjust the speed of the turntable to 50 HZ operation.

My question is... on all the european stuff I know what caps to change onsite and the ones that are usually ok but never having worked on US stuff its all new to me. I am guessing I should change any paper and wax caps as well as the white plastic ones and the "bumble bee" ones?

Any help info or advice would be greatly appreciated. it looks like a good console and looking forward to hearing how it sounds..

Eddy


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sun 19, 2019 5:45 pm 
Member

Joined: Jan Wed 16, 2013 12:04 am
Posts: 1618
Location: 77001
Welcome to the Phono Forum.

As you stated, all wax/paper or plastic covered caps,
electrolytic capacitors, replaced.

Power resistors/resistors
checked for wnl specs for this unit.

Circuits service data & parts found in Sams Photo fact 627-9.

Does this console have the reverb circuit ?!

Hotwax


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sun 19, 2019 6:09 pm 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
Hello Hotwax

Thanks for your reply yes it does have the reverb tank fitted. Where do I get the sams photo fact?

I can post photos if that helps any... sorry for all the questions!

Eddy


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sun 19, 2019 6:50 pm 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
photos

Image
Image
Image
Image
Image


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sun 19, 2019 7:13 pm 
Member

Joined: Jan Wed 16, 2013 12:04 am
Posts: 1618
Location: 77001
Wow ! That is definitely a TOTL Zenith for 1962 !

In-house made Zenith clam shell changer, and the
speaker system with the horns.

This will sound GREAT when completed.

See my PM to you.

Hotwax


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sun 19, 2019 7:28 pm 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
I assumed it must have been a good model for someone to go to the effort of importing and converting it to work here in the UK.

The cabinet is a little shabby but it will clean and polish up nicely but the fabric on the speaker grill is torn up in one corner and im not sure how i can get to replace that just at the moment...


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Mon 20, 2019 7:36 pm 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 107
stubbyeddy wrote:
Hello


Any help info or advice would be greatly appreciated. it looks like a good console and looking forward to hearing how it sounds..

Eddy


Hi Eddy,

I have the exact same hybrid belt/idler record changer, which was manufactured in 1961.

I have fully restored that changer (tear down, relube, rewire, new cart etc), and can answer any questions you may have about it.

Post a picture of the underside.

Based on the motor you are likely to have, you will likely need an FRX 21.6 belt for best speed accuracy. You will want to have the idler wheel rebuilt. Gary Stork at Voice of Music in the USA can supply both.

You will want to rebuild the motor. I can walk you through this if you haven't done it before.

Zenith literature from 1961 stipulated that the Euphonics cartridge (which has an LP and 78 flip stylus) in this specific Zenith idler/belt hybrid changer is supposed to track at a whopping 6 grams! There is a screw in the top right rear of the tonearm to adjust spring tension and set tracking force.

I installed some new old stock replacement styli for the Euphonics cartridge to test it out. The replacement styli were branded as Astatic (which acquired Euphonics in the late 1960s).

However, I wasn't impressed with the sound quality of the Astatic styli. I'm guessing that the ceramic elements and / or suspension of the Euphonic cartridge and / or replacement styli don't age well. I'm sure the cart/stylus sounded better when it was new. But after decades of sitting around, the Euphonics/Astatic combo sounded truly awful.

So I removed the Euphonics cartridge and replaced it with a period correct ceramic 1961 Sonotone 9TA cartridge, which sounds fantastic in this changer! I suspect the Sonotone 9TAs were much better made than the Euphonics and as a result still perform well to this day. You can find new old stock Sonotone 9TA cartridges on eBay from time to time.

Note the higher mass of this 1961-1962 Zenith "Custom Cobra" arm requires the lower compliance 9TA cartridge (and not the higher compliance 9TAHC model). The 9TA will track well in this arm at about 4.5 - 5 grams (about 1 to 1.5 grams lighter than the Euphonics). Aftermarket styli options for the 9TA are plentiful and the Sonotone 9TA is far superior sonically to the Euphonics.

Many consider the Sonotone 9TA to be the finest ceramic cartridge ever made.

If you change the cartridge, I would recommend sticking with a ceramic (like the 9TA) so you can use the Zenith preamp phono input. If you install a magnetic cartridge and use an outboard phono preamp and route the signal into the Zenith's tape input, you may end up with hum from the two pole motor. This is another reason why I would stick with a ceramic cartridge, as they are immune to motor induced hum.

I also rewired the tonearm (since the 9TA has different connectors than the Euphonics) and used KAB SuperFlex cable from KAB USA. I used four lead wires instead of the original three wires/ground strap. I terminated the two ground wires to the common post on the terminal strip under the chassis.

With a Sonotone 9TA cart installed with a new old stock yellow colored flip stylus (not grey HC stylus) tracking at 4.75 grams, I think you will be very pleased with the sound the turntable delivers.

Later Zenith hybrid belt changers (beginning in 1962) tracked at 2 grams (using Zenith's own cart) instead of 6 grams of the 1961 model (using the Euphonics cart). If you prefer to track lighter, you could buy and install a 1962-1969 era Zenith belt/idler hybrid MicroTouch 2G changer in your console. The only modification you would need to make is to enlarge the cut out of the wood support beneath the changer (to the left of the power switch) to accommodate the auto stylus cleaning brush mechanism found in all the 1962-1969 models. Otherwise, the changer footprint should be identical.


Last edited by zenithconsole on May Mon 20, 2019 8:26 pm, edited 24 times in total.

Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Mon 20, 2019 7:40 pm 
Member
User avatar

Joined: Mar Sun 11, 2007 6:55 am
Posts: 11214
Location: Mission Viejo, southern California
It looks like a nice project. Those ceramic disc capacitors are probably good, wile the "bumblebee" and foil&paper units dipped in wax are surely bad. You may also wish to replace resistors, as some may be far off of the proper value.

_________________
many of my radios http://s269.photobucket.com/user/FSteph ... t=3&page=1


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sat 25, 2019 11:00 pm 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 107
How is your project coming along? If you don't want to track your records at 6 grams with the Custom Cobra / Euphonic combo, you could always hunt down a period correct Zenith MicroTouch 2G (2 gram) belt drive model. I think Zenith even made some 2G models around 1962 and 1963 that are the same color as your 1961 Cobra model. In addition to tracking at a much lighter weight, the 2G models also have the cool stylus brush which raises up automatically to brush the needle and then the brush sinks back down out of sight. Probably the coolest changer ever made!


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sun 26, 2019 4:50 pm 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
Hi everyone

Yes everything is coming along nicely, its going to take me a bit of time this project as im also in the middle of house renovations, I have started recapping and still have a way to go then it will be checking resistor values and powering her up again. once I have the amp and radio working ok then I shall worry more about the turntable.. I have managed to strip it down clean and lubricate it no problem and it still works as it should so that another step forward..

I shall keep you all posted as I make progress

Eddy


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Sun 26, 2019 11:40 pm 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 107
The graphic below is from Zenith promotional literature noting that Euphonics cartridge in the 1961 Custom Cobra arm is supposed to track at 6 grams.

Attachment:
6grams.jpg
6grams.jpg [ 158.5 KiB | Viewed 1120 times ]


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Mon 27, 2019 2:27 am 
Member

Joined: Sep Thu 20, 2007 3:16 am
Posts: 936
Location: Winter Park, Florida
That Euphonics cartridge has a tracking range of 2-6 grams. I have found they track perfectly at
3-4 grams, even modern heavily cut records, so you could lower the weight. I have always been puzzled as to why Zenith specified the maximum.


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: May Mon 27, 2019 2:59 am 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 107
orthophonic wrote:
That Euphonics cartridge has a tracking range of 2-6 grams. I have found they track perfectly at
3-4 grams, even modern heavily cut records, so you could lower the weight. I have always been puzzled as to why Zenith specified the maximum.


I’m thinking Zenith may have recommended 6 grams of force because the 1961 “Custom Cobra” arm was fairly high mass. It seems to have the heft of a ROK broadcast tonearm.

The 1961 redesigned “Custom Cobra” arm must have been a stop-gap until the new vertically integrated Zenith 2G tonearm and cartridge were ready to commercially deploy in 1962.

Even if it was a stop gap, the 61 Custom Cobra was a quality redesign, and it tracks like a bloodhound.

I installed a Sonotone 9TA in my 61 Stereo Professional model, and it tracks best at 4.75 grams.

I actually find the added heft of the 61 Custom Cobra to be an advantage over the 1962-69 2g arms, because the higher tracking forces of the 61 model are better for tracking 78s and used, worn and scratched 45s and LPs. And with a higher tracking force, you don’t have to worry about the velocity trip friction dog pawl causing mistracking at the end of the record.

That said, the 2G models are awesome in their own right. Love that auto stylus cleaner!


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: Oct Wed 16, 2019 3:58 pm 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
Ive been working away doing a full recap of this and at long last I have finished!!

There is life and the am, fm and phono/tape all work ok as does the treble bass and presence BUT there are a few issues

The reverberation unit does not work at all ive connected up the tank but nothing and turning the knob doesn't do anything any idea where to start?

also one channel is very bass heavy and the other got lots of high end however if you turn the presence control up to max is takes all the bass off the one channel and makes it more or less in line with the other very strange... any idea where to start fault finding?

Other than that its working ok the fm decoder is working and its got good stereo sound on a strong station..

Im not used to working on US gear so any idea and help would be much appreciated

Thanks

Eddy


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: Oct Mon 21, 2019 9:40 pm 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
I've made great progress with the Zenith, its all working as it should all be it a few small issues which I hope to solve in the next week or so and will update accordingly.

My question is what belt do I require for the record changer, the one on it although working is a bit to slack and im at a loss as to what model or type of belt I should be looking for


all help appreciated

Eddy


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: Oct Mon 21, 2019 10:46 pm 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 107
stubbyeddy wrote:
I've made great progress with the Zenith, its all working as it should all be it a few small issues which I hope to solve in the next week or so and will update accordingly.

My question is what belt do I require for the record changer, the one on it although working is a bit to slack and im at a loss as to what model or type of belt I should be looking for


all help appreciated

Eddy



You likely need a FRX21.6 belt, available from Voice of Music. Post a photo of your motor under chassis.


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: Oct Tue 22, 2019 4:53 am 
Member
User avatar

Joined: Mar Sun 11, 2007 6:55 am
Posts: 11214
Location: Mission Viejo, southern California
Is is quite a nice find. Please post when it is finished.

_________________
many of my radios http://s269.photobucket.com/user/FSteph ... t=3&page=1


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: Oct Wed 30, 2019 2:52 pm 
New Member

Joined: May Sun 19, 2019 10:24 am
Posts: 8
At long last I have come to the end of this project, all is working perfectly and as intended!

After the first initial recap I discovered a few issues, first something was wrong with the presence control on the right channel, lots of bass on the one channel and nothing on the other, and the reverberation was not working at all..

The fault with the presence control was due to a bad pot. I managed to solve this by bridging it with a resistor setting the one channel presence to the center position so in time I can replace the whole pot assembly but as the control is little used and mostly always in the center position its not much of a concern..

The lack of bass was due to a open circuit ceramic disc cap in the audio signal stage, I changed the one and its pair one on the other channel and that sorted the issue.

The non functioning reverb was traced down to 2 open circuit resistors replacing these solved the issue

lastly I did replace the tubes in the reverb amp and one in the FM section and all now is working perfectly

I have made a youtube video of it in action, sadly I had to mute some of the audio because of copyright blocking the video but it still gives a good idea of how it all sounds now..

https://youtu.be/s7fIKvBSU7g

Thanks to you all for all your help it would have taken me much longer without it!

Eddy


Top
 Profile  
 
 Post subject: Re: Zenith MH2685 Console Repair
PostPosted: Oct Wed 30, 2019 5:22 pm 
Member
User avatar

Joined: Mar Sun 11, 2007 6:55 am
Posts: 11214
Location: Mission Viejo, southern California
Nice video! That was apparently a deluxe unit when it was new.

_________________
many of my radios http://s269.photobucket.com/user/FSteph ... t=3&page=1


Top
 Profile  
 
Post New Topic Post Reply  [ 19 posts ]  Moderator: Alan Voorhees

All times are UTC [ DST ]


Who is online

Users browsing this forum: startgroove and 3 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB