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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Sun 01, 2013 5:45 am 
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azenithnut wrote:
Just want to consider all my options
Easy to say when it's not my money, but I'd lean toward rewinding or having a new one made to spec.

Yet another option -- this might be a long shot, but I've been told this outfit has loads of old transformers, who knows, maybe even some NOS:

http://www.oldradioparts.com/

In addition to part numbers, I'd give 'em whatever specs you have for the transformer. Costs nothing to ask, right?

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Mon 02, 2013 2:55 pm 
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azenithnut wrote:
Well, the power supply is gone, I'm surprised it sold the day after I find it! I contacted the seller to be sure.

I wonder who bought it?

So, onward to either find a place to rewind it, or rewind it myself.

-Steve


I was just catching up on your thread, and am impressed with how you've dug into it already.

And also surprised there was a power supply on ebay. Wow, that was serendipitous!
If it was an original, correct to the schematic, it could have been a blessing. Sorry that you missed it. Dang.

The seller was Mitchell Manger. I've forwarded his telephone number to you via PM.

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Mon 02, 2013 4:21 pm 
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Jeff Thomas wrote:
azenithnut wrote:
Well, the power supply is gone, I'm surprised it sold the day after I find it! I contacted the seller to be sure.

I wonder who bought it?

So, onward to either find a place to rewind it, or rewind it myself.

-Steve


I was just catching up on your thread, and am impressed with how you've dug into it already.

And also surprised there was a power supply on ebay. Wow, that was serendipitous!
If it was an original, correct to the schematic, it could have been a blessing. Sorry that you missed it. Dang.

The seller was Mitchell Manger. I've forwarded his telephone number to you via PM.


Thank you, but I was already told its gone. That surprised me that it sold so quickly. Yes, I agree, it would have been a real help!
Hindsight is 20/20...

-Steve

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Mon 02, 2013 5:13 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
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Location: Champaign IL 61822
I'd love to see the schematics of more than the power supply, interesting
as that is. I found several net links but they are all "404".

Does anybody have a pointer?

As to shunt regulators ... they are about as common as water, since
they were used as the HV regulators in tube color TVs.


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Mon 02, 2013 5:25 pm 
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Schematics can be found here, though they are a little hard to read in some cases, but it will give you a general idea.

https://sites.google.com/site/hammondno ... nformation

I wouldn't say the power supply uses "shunt regulation" as there really is no voltage reference to regulate to. I would call it "active filtering". it seems that Hammond had a thing against using electrolytics. I can understand that very well as I don't like them either. :lol:

-Steve

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Mon 02, 2013 5:58 pm 
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Location: Champaign IL 61822
How on Earth do the dividers work?


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Mon 02, 2013 6:06 pm 
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dtvmcdonald wrote:
How on Earth do the dividers work?


They are a non-linear amplifier biased with a time constant so that they miss every other cycle from the previous divider. Therefore each one has to be tweaked for the frequency they are being fed. This is done with clip-in resistors in each divider/control tube compartment. I wonder how tedious this process will be?

-Steve

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Tue 03, 2013 2:29 am 
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That's an interesting divider circuit. I got it to work in a simulator
(using a 12AX7 model).

The adjustment of the resistor is easy: clip in a pot
and adjust until it works right, then install the correct fixed resistor.

The waveform the simulator makes is not exactly clean ...
its a fast fall then an exponential rise (at the plate). The
waveform at the cathode is even crappier.


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Sep Tue 03, 2013 1:03 pm 
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Yeah, that is what gives the Novachord its unique sound. Rich in tube harmonics. :wink:

Each oscillator and every divider run continuously. Therefore there are 72 notes being generated all the time the instrument is turned on. The output of each note is turned on and off by the control tubes, again, 72 of them.
They all are mixed together in a 72 channel mixer and fed through the filters and control panel then to the preamp and finally the amplifier chassis.

All this plus several filters, attack and decay adjustments and a mechanical vibrato to modulate the oscillators.Quite a feat of engineering for the 1938 time period!

-Steve

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Oct Sun 06, 2013 11:20 pm 
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Not much progress yet. Money has been tight and I've been trying to get things ready for Winter to arrive.

I spent this weekend changing the wiring so it will be a little more practical to work on things. The wonderful "wires stuck into a receptacle" feature is gone, replaced by a wall switch. The outlet strip has a switch above it to select whether I want the strip on all the time, or to come on and off with the light switch by the door. There is also an outlet receptacle on the post which can be seen at the corner of the bench in the pic. The bench needs to be moved to the post which will center it below the outlet strip better. But, I cannot move it myself and I have nobody to help. It really sucks to not have any friends or family nearby... :(

Anyhow, just a note as I am NOT giving up on this project. I am about to contact Heyboer as well as Hammond to see about rewinding the power transformer. I also still need to take an inventory of capacitors and resistors to figure out what I need to order from Digi-Key or Mouser.
Progress is slow, but this is expected.

-Steve


Attachments:
electric-bench.jpg
electric-bench.jpg [ 94.58 KiB | Viewed 4795 times ]

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Oct Sun 06, 2013 11:45 pm 
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Glad to see you sticking with it. It's a big project, but a rewarding one.

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Oct Sat 12, 2013 6:05 pm 
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Power supply seems to be a madman's delight. I think pre LSD.


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Oct Sun 13, 2013 5:08 am 
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That is one crazy power supply design, and certainly not your run of the mill design for that time period. Honestly I don't know that I've ever seen anything quite like that from any time period. Everything I have ever heard about the Novachord says it was a stunning feat of engineering, and the power supply design fits into that statement.

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Oct Mon 28, 2013 4:32 pm 
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Hello All - My name is Joe, and I'm brand new to this forum. I haven't gotten into antique radios, but I am the proud owner of TWO Hammond Novachords, s/n 1490 and s/n 1776. I've been rebuilding the latter for quite a while, and I'm glad to say it's nearing completion.

I stumbled onto this thread through a Google search, and if I can help with any questions, let me know. I've made a few contacts over the past three years, and I'll post a few links when I can (at work right now).

- Joe :-)


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Oct Mon 28, 2013 6:12 pm 
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Hello Joe!
Thank you for your offer! As of now, your the ONLY one I have made any kind of contact with who has and/or has restored one of these.

I've sent several e-mails out to other owners without a single response.

Currently, I'm looking to have the defective power transformer rewound or a complete new one made. My first contact will be Hammond of Guelph Ontario, but I also plan to contact Heyboer as well. The only reason I have not contacted them yet is the fact that I dug myself a bit into debt on my credit card and wanted to get it paid off before I start. That should be happening within a couple weeks.

I've also been working (as time permits) to prepare the area I will be working on it for cold winter months.
This is simply too large and too lengthy a project to tie up my normal workbench. It will be in the garage as the photos show.

I'm glad to see the one you are restoring is a late model like mine, so you will be more familiar with it if I have questions.

Thanks and welcome to the Antique Radio Forums!

-Steve

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Oct Mon 28, 2013 6:34 pm 
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Hello Steve -

Glad to be of any help I can. I've got the complete service manual with all the schematics if you'd like a copy, and if you haven't found Dan Wilson's excellent thread at Vintage Synthesizers, you can find it at vintagesynth dott comm, and do a search for "wakeup". I'll post a link as soon as the forum here knows I'm not a spammer.He's got some very good info, including transformer replacements for his PSU. Unfortunately, he had them done in England, but he might be able to help with the specs.

- Joe :-)


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Feb Mon 24, 2014 10:58 pm 
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Joe, I want to thank you again for the heads up on the power supply that was just on ebay.
I won it and it is on its way.

http://www.ebay.com/itm/191074228044

I just hope the power transformer (Second from the left) is good... <fingers crossed>

I have not given up on this project. Money issues as well as it being so bitter cold this winter has kept me out of the garage where the Novachord is located. Even though I have been keeping the area under the loft warmer at about 50 degrees, that bitter cold air clings to the floor and it is just too uncomfortable to work. I have enough trouble keeping my feet warm as it is!

-Steve


Attachments:
novachordps1a.jpg
novachordps1a.jpg [ 60.42 KiB | Viewed 4455 times ]

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Feb Mon 24, 2014 11:37 pm 
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Steve, I didn't know about the power supply on the auction site. But I am glad for you that it went for what I would call a reasonable price. Glad for you. Yet another step along the way. No good project seems to be completed "easily" does it?

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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Feb Wed 26, 2014 1:46 pm 
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Steve - Congrats on winning the auction.

Here's a picture of my PSU for s/n 1776 after I cleaned it up, replaced all the passives and rewired it with Teflon wire:
Attachment:
Rebuilt PSU 2 - Low Res.JPG
Rebuilt PSU 2 - Low Res.JPG [ 66.13 KiB | Viewed 4412 times ]


- Joe :-)


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 Post subject: Re: 1939 Hammond Novachord - Unrestored
PostPosted: Mar Sat 01, 2014 10:23 pm 
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Thanks for posting your power supply! That's quite the showroom piece! I may keep the black wrinkle finish on mine, not sure yet.

Got the power supply.
So far the transformers check out just fine. I simply removed the rectifier tubes, then brought it up on a Variac until the high voltage on the 5V4 tube socket was at the voltage written on the schematic.
Then checked all other windings for proper voltage.
They were all within reasonable tolerance. Most often transformers will produce a significantly higher voltage when unloaded, so keeping the primary down should reduce any chance of failure.

After on for a while, no sizzling sounds, smoke or smells. Though, I'm rather stuffed up with a cold right now... :(

The chassis is completely unmolested! Just the way I wanted! :D
The only issue was the one corner of the chassis was bent. It was NOT bent in the ebay photos and there was no evidence of shipping damage. Oh well, such a minor issue. I'm not complaining.

This takes things one step further. many many more to go.

-Steve


Attachments:
novachordpowersupplynew.jpg
novachordpowersupplynew.jpg [ 136.22 KiB | Viewed 4366 times ]

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