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Another 1000Z Stratosphere Restoration

4/13/2017

13 Comments

 
I have accepted another Strat restoration project.

This radio belongs to Jeff, a long time local collector. He would like the chassis to remain as original in appearance as possible while still functioning like new. (Not too big of a challenge).

I believe this restoration to be critical in preserving the history of one of these iconic examples of American innovation and industrial prowess in the early years of radio. For this, I have made an exception to the "no outside projects" statement on the home page.

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SO, here we go - -
This restoration may seem a little slow since I can only spend a short time over the bench on any day - getting old is a PTA, but this gives me time to accurately update this blog.

The 1000Z has 2 major chassis, The RF chassis (above) and the Power Supply/Audio Amp chassis. Additionally, the output/crossover chassis has some critical, custom, parts that must be serviced.

I have begun work on the receiver (RF) chassis and will post updates as the project progresses.

HOLD it right there - Well, after a closer examination, we have decided to replate (chrome) the receiver chassis. This is a huge amount of additional work, but it would be a shame to have the restored chassis looking like this:

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Today, the documentation and removal of ALL of the components from the chassis has begun.

The dog-bone replacement resistor kit for this chassis is finished.

Updated pictures as the chassis is stripped of all parts -
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Very few issues have ben found so far - which is nice.
One of the filter caps has blown the top off - will have to fix or find replacement.
The relay that enables/disables the audio in the muting circuit has an open coil (just like on mine and I suspect many others). It will be rewound.
A few of the original "paper" caps have been replaced - I will use the artwork created in the earlier restoration to build correct-looking replacements.
Chrome - as noted above.
Further deconstruction and testing reviled an issue with one of the interstage transformers.
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Portion of the schematic form Nostalgia Air showing the relationship of the 2 interstage transformers
Note that two 76s drive two 42s  driving eight 45s (not shown).


Below, the deconstruction process continues.
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The tube sockets are secured by a snap ring. This means that the sockets must be unwired before they can be removed from the chassis through the top.
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These are the Bradley volume and tone controls. The volume control includes a section for base contour (loudness) that increases the bass level as volume decreases and decrease base as volume increases until about 3/4 volume. At this point the base boost is nil but still controllable by the tone control.

I have not seen these exact units in any other radio. It would be fair to say that replacements would be very valuable. There is no indication that these are damaged.

The trip lever on the shaft of the volume control is used to switch the radio on/off. Needing to switch 350W, I believe that a suitable combined volume on/off switch was not available.

Resistor kit for the receiver chassis below. Even though some of the original dog-bone resistors were 1/4 W the replacements are no smaller than 1W, mostly 2 & 3 W (regardless of size).
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Below are pictures of the variable bandwidth IF transformers and a video showing the mechanics of their operation. Wider IF bandwidth allows the radio to detect more of  the modulation resulting in  better fidelity which is quite noticeable in the treble range. The drawback is worse adjacent channel rejection. You might also notice that a signal is slightly stronger when the IF is set to wide.
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Only things left now are the tuning cap and band switch. I had left the shield on to protect the cap, but it can come off now.
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The deconstruction is done. I can work on repairing the defective parts and on the power/amp chassis while the main chassis is off to the chrome shop.
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Band switch and tuning cap removed.
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Needed to drill out a few rivets. Above, fiber guides for the variable IF adjustment shaft. AND - NO, I didn't drill out the holes to the right. This seems to be factory. Maybe they needed to enlarge the holes after the original plating process.
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Receiver chassis all ready to go off to the plater's.
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Above is the QAVC circuit being discussed in the comments (below). The relay is item 12. Courtesy of Nostalgia Air.
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QAVC relay, still needs to have the coil rewound.
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Here is the QAVC relay with it's new coil.

At this point, I am going to begin work on the power/amp section and will start a new blog entry.
13 Comments
Harry link
4/13/2017 01:31:04 pm

I've got a 1955 five tube set I need a rush job on. Mailed it yesterday. LOL

Reply
Russ
4/15/2017 09:26:50 am

Tell you what, Harry. I'll have it chromed and add a few more tube sockets to your radio - to make it respectable ;-)

Reply
Harry link
4/15/2017 10:32:08 am

You should make a full length movie of this rebuild Russ. The credits can include Sue & Fuzzy. The climax is when you finish the alignment and tune in a local broadcast only to discover you've been transported back in time to 1935 only you're still old and no one has yet heard of Medicare.

Reply
Russ
4/17/2017 11:40:35 am

Harry, Sometimes I find long how-to videos hard to watch. In small segments a person can choose which to watch without loading down their connection or mind ;-)

John Goller, k9uwa link
4/20/2017 07:17:36 am

Russ enjoying your Blog and pictures. I have done two of these 1000Z radios in the past. Fortunately never had to totally take one apart for rechroming. Question for you about my own 1000Z. My mute relay sticks. It mutes correctly but sometimes it won't unmute unless I thump the cover of the relay. Any ideas on how to fix it?
Thanks
John k9uwa

Reply
Russ
4/20/2017 07:41:30 am

John,

Two possibilities come to mind. As I recall, there is a 79 dedicated to this QAVC circuit. It may be that it is being biased on even when it should be off. Does adjusting the setting on the back of the set make any difference? You might want to check voltages on this tube and the 85 ACV tube (yeah a PITA) or just swap it out and try operation.

The second possibility is that the return spring has become weak or broken. I had a real problem with the springs in my radio since it had been subject to moisture. The springs on the adjustable IFs (above) were both corroded and one was broken. The spring material rusts very easily. Might want to check the relay return spring.

C2 leaking could also do it. But if you recapped it - probably not. I suppose that Occam's razor would also suggest checking R16, the QAVC adjustment.

Reply
Russ
4/20/2017 07:44:34 am

I'll post a picture of that relay today. I need to rewind the coil on it anyway.

Harry
4/21/2017 07:15:33 am

Russ, I have a Stewart Warner chassis that I used for parts several years ago that has the same "trip lever" on the volume control shaft to turn the set on/off.

Reply
Russ
4/21/2017 08:24:10 am

A lot of the early radios that combined the volume with the on/off function had separate switches in the beginning. I believe that this was simply because the more modern control design had not been invented yet.

I think that, on this radio, the throw-back to the earlier design was necessary due to the large power requirements. There was probably no integrated volume/on/off control with contacts rated for 350W. Or it was too large, expensive or some other manufacturing issue.

Reply
Tony Kriwokulski
4/22/2017 04:39:51 am

I am really enjoying this series. It is nice to see someone take their time a do a job the right way. Keep up the great work.
As for the Bradley controls, I have seen them in 1932-1933 RCA radios. My RCA R90 has 3. One for volume, one for Bass, and one for Treble. They are really high resistance values. Hopefully your are ok.

Reply
Arran
4/22/2017 10:54:36 am

Those might be wire wound internally, I have some G.E sets around the same vintage and that was what they have for the volume and tone controls. I'm not sure whether they are A-B made controls or not, in one set some fumbler broke the phenolic cover on the back to get at the inside, I assume for cleaning purposes.

Reply
Russ
4/22/2017 11:25:46 am

Those controls have carbon discs sandwiched between metal discs. The metal discs make contact with the wiper(s) so the carbon discs don't need to. It is a fairly durable design with the most important factor being correct tension (compression) of the discs.

Paul Wimmer link
6/13/2017 04:46:13 am

Russ, Very nice work on the Strat. Enjoy seeing everything coming apart down to the bare chassis and then back together again.
A real learning experience for us being able to see work done at that level of detail.
Paul (processhead)

Reply



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CUSTOM DESIGN BY SUE WEBB  06/2013       Redesigned by Russ Webb     Approved by Fuzzy   Updated:  Pretty much all the time, but I forget to change this date
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