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 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Sun 15, 2013 6:15 am 
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I've used cut lengths from the larger sections of a junkbox Transistor AM/FM radio's telescoping antenna to extend control shafts.
The correct size works snug enough so that no adhesive is required to hold it in place.

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 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Sun 15, 2013 6:23 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
    Thanks Brett---I remembered that thread well once I read it ! Guess it isn't obvious in pic, but the 475 & 705 shafts are 1/8" (or possibly slightly less) O.D.---but thinking along the same line, could use rigid tubing over control shaft with a 1/8" I.D. bushing or piece of standoff with O.D. same as I.D. of tubing inserted within... Am going to dig through both electronic & mechanical "junkboxes" soon. Fortunately, there is adequate clearance between chassis and front panel for all of this...

    Wow---just started to post and saw Fifties novel idea ! Think I have some old telescoping TV antennas in cabinet... Have to grab my tubing cutters from plumbing toolbox... Will still have to find a suitable bushing for insert---but could always use several "mating" pieces of the antenna to build it down to (or close to) original shaft size.

    John


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     Post subject: Re: Zenith Royal 705 "project"...
    PostPosted: Dec Sun 15, 2013 7:15 am 
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    Joined: Aug Wed 24, 2011 4:35 am
    Posts: 4027
    Location: Sunnyvale CA
    xrhonda91 wrote:
      Thanks Brett---I remembered that thread well once I read it ! Guess it isn't obvious in pic, but the 475 & 705 shafts are 1/8" (or possibly slightly less) O.D.---but thinking along the same line, could use rigid tubing over control shaft with a 1/8" I.D. bushing or piece of standoff with O.D. same as I.D. of tubing inserted within... Am going to dig through both electronic & mechanical "junkboxes" soon. Fortunately, there is adequate clearance between chassis and front panel for all of this...\


      You can get the same sort of brass tubing in a range of sizes from 1/16 to about 3/4" in sizes that telescope perfectly inside the next larger size. Very useful!

      Brett


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Dec Wed 25, 2013 12:54 am 
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      Joined: Oct Mon 26, 2009 10:02 pm
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      Location: Indianapolis, IN
      Replaced all electrolytics in this radio today, but didn't have time to check it out. Still need to find a very low current coil reed relay to switch the battery "tap" circuit since new switch is only SPST... Also need to complete the volume control shaft modification...

      It's gettin' there...

      John


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Dec Wed 25, 2013 1:47 am 
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      Joined: Aug Wed 24, 2011 4:35 am
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      Location: Sunnyvale CA
      xrhonda91 wrote:
      Replaced all electrolytics in this radio today, but didn't have time to check it out. Still need to find a very low current coil reed relay to switch the battery "tap" circuit since new switch is only SPST... Also need to complete the volume control shaft modification...

      It's gettin' there...

      John


      I have been trying to work out how to use a latching relay for this application, triggered by a high-pass filter to turn on, and some diodes to use the cap charge to make it turn off. That way you don't have any current draw from the relay while it is playing.

      Brett


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Dec Wed 25, 2013 9:42 pm 
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      Joined: Jan Thu 01, 1970 1:00 am
      Posts: 550
      Location: N.E. Florida
      John,

      PM me if you can't find a reed relay laying around. I have some that are in DIP form.


      Jay


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Dec Thu 26, 2013 2:27 am 
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      Location: Indianapolis, IN
      Thanks much, Jay... We use a bunch of SIP reed relays at work which have coils that pull about 10 mA when activated, but am trying to find one which only requires around 5 mA @ 6V.

      Like Brett's idea about a latching relay but am also wondering about using a FET for switching---the gate current should be miniscule and it might work. Need to think it through...

      John


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Dec Thu 26, 2013 3:05 am 
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      Joined: Aug Wed 24, 2011 4:35 am
      Posts: 4027
      Location: Sunnyvale CA
      xrhonda91 wrote:
      Thanks much, Jay... We use a bunch of SIP reed relays at work which have coils that pull about 10 mA when activated, but am trying to find one which only requires around 5 mA @ 6V.

      Like Brett's idea about a latching relay but am also wondering about using a FET for switching---the gate current should be miniscule and it might work. Need to think it through...

      John


      2 FETs, but yes, that should work. I was going more for a Atomic Age solution.

      Brett


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Dec Sun 29, 2013 4:46 am 
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      Joined: Oct Mon 26, 2009 10:02 pm
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      Location: Indianapolis, IN
      Hello All,

      Spent most of the day modifying volume control shafts for this and the Royal 475. Made a "jig" from a block of oak and various pieces of metal from junkbox to support the shafts for filing. Screwed small metal strips of the proper thickness on both sides of shaft to act as guides for file to ensure "flatness" and that the proper amount of metal would be removed. Did one side, turned over, "sighted" for proper orientation, then filed the other. Had to exercise great care since these shafts are not replaceable, so it took a lot of time and a few changes in the guide strips' thickness to get it done... Then had to "fine file" a few strokes at a time to get the new tab to fit snugly within the split shaft of new controls---and the fit is tight enough that no glue required. The original shafts pass through small holes in front panels which act as guides to maintain their positions.

      Also, had to re-glue the aluminum tuning dial onto plastic "base"...

      Am still debating on whether to use a relay or FETs to switch the supply "tap"... But radio is completed up to this point.

      Will post pics when all done, so stay tuned...

      John


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Wed 08, 2014 8:59 am 
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      Joined: May Mon 17, 2010 6:47 am
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      Location: Dowagiac, MI
      I'm interested to see how this pans out, I have a 705 with issues on the low end of the volume pot. Cosmetically its pretty beat up, but plays quite well (aside from volume issues). Caps are still original, and no alignment has been performed.

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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Thu 09, 2014 3:07 am 
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      Joined: Oct Mon 26, 2009 10:02 pm
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      Location: Indianapolis, IN
      Hello Frank,

      The Royal 705 is another of Zenith's great performing radios---definitely "Super-Radio" class ! Mine also worked with original caps, but decided to replace while it was apart.

      Am still waiting to get a relay for switching supply "tap"...

      Am sure looking forward to getting it (and others awaiting parts/repairs) completed !

      Be sure to let us know how yours is coming along...

      John


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Thu 09, 2014 3:17 am 
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      I'm probably not gonna do much to it anytime soon. I am considering mounting a small DPST switch on the back or side since mine is cosmetically in very poor condition. My thought on that is because it will allow for better battery life, though the FET solution for adapting a SPST switch seems enticing if it doesn't have much effect on battery life.

      Been off work for two weeks with a knee injury so money is real tight right now.

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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sat 11, 2014 5:12 am 
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      Joined: Oct Mon 26, 2009 10:02 pm
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      Location: Indianapolis, IN
      Frank---if it is that bad cosmetically, a DPST switch from junkbox would be a good idea. You could mount it out of sight on back cover...

      I thought the other day about some old SPDT lever-activated micro-switches in junkbox and that an "actuator" could be added to new switch shaft below where modified old one "mates" with it... The NC contacts could be used and the "actuator" would contact lever at CCW end of shaft rotation to turn it off...

      Got the parts on bench for "project" tomorrow---stay tuned...

      John


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sat 11, 2014 5:39 am 
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      Alright, looking forward to the results!

      I will post some pics of mine when I get the chance to see what other people think, but the grille is pitted and dented in a few places, and the carrying handle is cracked halfway thru. Also, the knobs have a couple chips in the plastic.

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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sat 11, 2014 10:00 pm 
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      Joined: Jan Thu 01, 1970 1:00 am
      Posts: 550
      Location: N.E. Florida
      John,

      It looks like your are thinking this thing too much. Your relay idea draws around 10ma. Even if you used this radio as a daily listener, 10ma is hardly anything to be concerned about with AA cells, right?


      Jay

      Let's get to work on that 2000.


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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sun 12, 2014 5:55 am 
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      Joined: Oct Mon 26, 2009 10:02 pm
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      Location: Indianapolis, IN
      Well, Jay---spent several hours today engineering, installing, and "debugging" the micro-switch "solution" ! And it works great ! Overkill, I know---but that's usually the way I do "stuff"...

      Modified switch itself to fit within space (see "raw" switch at right side of 1st pic), cut and modified old nickle-plated brass mounting tab from an old multi-contact "stack" switch for an "actuator", found old phenolic PCB "joiners" which were already tapped for 4-40 screws to use for mounting, cut, filed & drilled small piece of steel strip for supporting one end, and drilled hole in radio chassis for other. After determining alignment of "actuator", Superglued it into lower portion of volume control's split shaft. Then aligned micro-switch assembly to "sync" with volume control's switch.

      Then "debugging"... Saw that control wouldn't rotate full travel because of actuator's "tail", so clipped it off (after chassis pics were taken). Installed chassis into radio and noticed an audio "pop" at a certain point while adjusting volume---removed and shortened faceplate mounting stud which I thought was culprit. Reinstalled and same thing ! Out it came again... Noticed a few component leads were very close to actuator as it rotated, so clipped them thinking that PCB must be flexing just enough when chassis mounted to cause short---and that was it !

      Well, it was worth it ! All is good and as mentioned earlier, this is an outstanding radio performance-wise ! Excellent sensitivity & selectivity all across band with very good sound for its size... And the vernier tuning on this is very easy & smooth. Sure glad it's done and thankful it turned out so well...

      Below are a few pics... Sorry about the poor "write-up", but am really tired... Any questions welcomed...


      Attachments:
      0 ARF ROYAL 705 COMPLETE.jpg
      0 ARF ROYAL 705 COMPLETE.jpg [ 231.79 KiB | Viewed 1466 times ]
      0 ARF ROYAL 705 CHASSIS COMPLETE.jpg
      0 ARF ROYAL 705 CHASSIS COMPLETE.jpg [ 204.71 KiB | Viewed 1466 times ]
      0 ARF ROYAL 705 SWITCH MOD EDGE VIEW.jpg
      0 ARF ROYAL 705 SWITCH MOD EDGE VIEW.jpg [ 218.91 KiB | Viewed 1466 times ]
      0 ARF ROYAL 705 SWITCH MOD (ON).jpg
      0 ARF ROYAL 705 SWITCH MOD (ON).jpg [ 222.57 KiB | Viewed 1466 times ]
      0 ARF R0YAL 705 SWITCH MOD (OFF).jpg
      0 ARF R0YAL 705 SWITCH MOD (OFF).jpg [ 228.88 KiB | Viewed 1466 times ]
      0 ARF ROYAL 705 SWITCH MOD PARTS.jpg
      0 ARF ROYAL 705 SWITCH MOD PARTS.jpg [ 164.94 KiB | Viewed 1466 times ]
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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sun 12, 2014 6:18 am 
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      That radio looks pretty good from here. Fascinating solution to the on/off issue! Well done :D

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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sun 12, 2014 6:42 am 
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      that's pretty crazy but sweet at the same time!

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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sun 12, 2014 7:38 am 
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      Nice engineering work, John! :wink:

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       Post subject: Re: Zenith Royal 705 "project"...
      PostPosted: Jan Sun 12, 2014 12:23 pm 
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      What an interesting solution! Great job, as always.

      Colin


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