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


It is currently Jun Tue 19, 2018 3:31 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 46 posts ]  Go to page 1, 2, 3  Next
Author Message
 Post subject: Zenith Royal 705 "project"...
PostPosted: Nov Thu 28, 2013 3:59 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Hello All,

This is another radio that I've been wanting to find for awhile and "stumbled across" on Ebay... It arrived today in pretty good overall cosmetic shape---somewhat dirty with moderate chrome pitting, but looks as though it'll clean up fairly well. The "Permawear" vinyl used on these does not age well and is brittle---every time I open rear cover, the "hinge area" seems to crack more... For some reason, original owner taped a note on bottom with purchase date and price---July 12, 1966 $31.00. They also wrote $31.00 on inside label... It is newer than what I typically "collect", but like it's appearance & of course, "love" that tuned RF amp stage !

From what I've found on-line, these seem to be DX champs and wanted to "play" with one... Same basic circuit as the Royal 475---but like its predecessor, the Royal 490, it has a significantly longer ferrite antenna rod and OTL audio output with a "split" 6V battery supply. The Royal 66 appears to be identical. The tuning knob is small, but the vernier drive has a very smooth & "easy" feel (I know, this statement seems out of place...).

Had hopes that this one would work at least somewhat as it was---but no such luck...
Installed batteries, turned on, and absolutely no sound whatsoever... Power getting through dual switch sections, oscillator activity clearly heard on adjacent radio, but zero audio---not even a pop or click ! Plugged in headphones with same result---silence... No time tonight to troubleshoot any further, but sure hope audio transistors okay. Even with bad caps, you'll hear a slight "click" if not more... Inside looks original & "un-tampered" with.

As always, any comments or experiences with one of these welcomed.

Here are a couple pics from the Ebay listing:


Attachments:
ARF ROYAL 705 INS.jpg
ARF ROYAL 705 INS.jpg [ 213.38 KiB | Viewed 3610 times ]
ARF ROYAL 705 FRT.jpg
ARF ROYAL 705 FRT.jpg [ 222.7 KiB | Viewed 3610 times ]


Last edited by xrhonda91 on Dec Sat 07, 2013 6:26 pm, edited 1 time in total.
Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Nov Thu 28, 2013 4:22 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Well Guys---guess I'm slipping a bit in late "middle-age" !

Am supposed to be getting ready to travel for Thanksgiving, but just had to investigate this radio a bit more before leaving...

One section of the power switch IS intermittent/resistive & after checking it and thinking it okay, guess it "re-opened" while I was listening for "activity" ! Also, the volume pot is "flaky"... Using my "orphan" coral TR-84's audio input as a signal tracer, found that the radio was indeed working up to the output, so jumpered the switch section which connects "center tap" of split supply to speaker and it came to life ! Played with the volume control a bit and this radio is outstanding ! Around 10 in the morning and was receiving, very clearly, stations all across the band---with excellent sound for size of the set ! And using original electrolytics... Now encouraged and excited to get this one completed...

The chassis design is excellent---with the removal of four 1/4" hex-head screws, it is easy to lift from case. Also noticed that the front panel is also easily removable for cleaning/detailing...

Stay tuned & have a Good Thanksgiving !

John


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Nov Thu 28, 2013 6:17 pm 
Member
User avatar

Joined: Aug Wed 26, 2009 1:50 am
Posts: 1366
Location: Mount Pleasant UT 84647 (from Coventry, UK)
And a Happy Thanksgiving to you too John.

Colin


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Nov Thu 28, 2013 10:32 pm 
Member

Joined: Nov Sat 22, 2008 3:04 pm
Posts: 2641
Location: Gormley, Ont., Canada
Happy Thanksgiving, John.

Bruce

_________________
Radio Zoomer


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Nov Sat 30, 2013 1:58 am 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4002
Location: Richmond, VA
Sounds like you will have it playing like a champ in no time. Zenith made some outstanding performers in the lunch box format.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Dec Fri 06, 2013 4:51 am 
New Member

Joined: Dec Fri 06, 2013 4:49 am
Posts: 1
I agree with you.
________________________________________
http://www.amazon.com/Pilates-Beginners-Ultimate-Guide-Mastering-ebook/dp/B010Q2GKQO/


Last edited by Elisa6871 on Sep Mon 28, 2015 11:51 am, edited 2 times in total.

Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Dec Sat 07, 2013 2:19 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Thanks All !

Ed---this radio is actually fairly small. About the same size as the Royal 475. You probably could "squeeze" a sandwich into it !

Am thinking about trying to remove switch assembly from volume control and repairing since it is a dual unit (DPST). Looks possible, but sure would like to know if anyone here has done it ??? May PM Brett Buck for his input...

Here are a couple pics of chassis before disassembly:


Attachments:
ARF 705 VOL-SW CTL.jpg
ARF 705 VOL-SW CTL.jpg [ 195.03 KiB | Viewed 3441 times ]
ARF 705 CHS.jpg
ARF 705 CHS.jpg [ 227.44 KiB | Viewed 3441 times ]
Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Dec Sat 07, 2013 4:40 am 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4025
Location: Sunnyvale CA
xrhonda91 wrote:
Thanks All !

Ed---this radio is actually fairly small. About the same size as the Royal 475. You probably could "squeeze" a sandwich into it !

Am thinking about trying to remove switch assembly from volume control and repairing since it is a dual unit (DPST). Looks possible, but sure would like to know if anyone here has done it ??? May PM Brett Buck for his input...

Here are a couple pics of chassis before disassembly:


I got your PM. I haven't taken one of this type apart, although I have disassembled the single-pole version. It was easier to get apart and back together than I expected.

I would point out that the type of VC/switch used in the 500E that lacks an output transformer, and any of the lunchbox radios with a "battery saver switch" is also a dual-pole (for the same reason, presumably) and will likely work, if you have one of those. I have a 500E parts radio with a bad resistance element but a good switch if you want to morph them together - your resistance element and my switch. If you take a clear side view picture of how the switch section is attached, I could see if it looks like it might fit. I sure looks like the same sort of attachment, but I would need to see it from the side where the tabs are. Mine has the terminals on the end, rather than the back, but it looks like there is plenty of space on that side. I have taken this type apart and it, too was no problem to get back together.

I understand your reticence, I figured as soon as I moved the tabs, something inside would go "sproing" and disappear into the carpet. But it was made to be easily assembled, so it's relatively safe to work on. Given the lack of likely candidates for replacements, I would just go ahead, pop it open, flood the switch section with contact cleaner, WD-40, or something through the hole where the cam goes in, and hope it clears itself up.

The other alternative is to see if Jim Barnard at transistor-repairs.com, or John Kendall at vintage-electronics.com has any salvaged working volume controls, for thos radio, or a 500E OTLess type.

Brett

p.s. here are some pictures. Your is a little out of focus but to first approximation, I think it might be the very same switch with the terminals in the side instead of the back.

Attachment:
royal500e_dpst_side.jpg
royal500e_dpst_side.jpg [ 209.66 KiB | Viewed 3434 times ]


Attachment:
royal500e_dpst_back.jpg
royal500e_dpst_back.jpg [ 221.52 KiB | Viewed 3434 times ]


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Dec Sat 07, 2013 3:26 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Thanks very much, Brett, for your response !

Sorry for the poor photo, but the control is covered with flux residue and I took pics without tripod---and that was the second "shot"...

It is the very same switch as you pictured---even has the slots for alternate terminal positions... Checked my 500E's and both have the SPST switch.

Will the retaining tabs on the side simply "snap" out with tip of X-Acto knife ? Are the "internals" of switch accessible through the cam hole ?

I have to admit that lately I've become more nervous & frustrated working on these---but having a hard time trying to "break" the habit. Have several "incomplete" projects now and need to get motivated to get 'em done...

Thanks again...
John


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Dec Sat 07, 2013 6:24 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Thanks to Brett's encouragement, I removed the control from radio and it disassembled easily. Used the "flat" side of X-Acto blade against switch body to release tops of tabs and inserted tip in gaps to carefully bend them outward just enough to remove switch.

The thin phenolic cover on bottom which covers the switch contacts is simply pressed onto housing "pins" and lifted off easily exposing "internals". The problem was then obvious---someone had decided to "oil" the switch assembly and it was practically full of heavy oil & sludge. Looked like 10W30 automotive "stuff" ! The thin switch contacts rely on spring tension to close and make connection when cam "releases" them and you could see how the "goo" was interfering with this. Also looks like the contacts could be removed for cleaning and a bit of "re-tensioning"...
Guess an Isopropyl alcohol "bath" is forthcoming !

More later---stay tuned...

John


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project" begins...
PostPosted: Dec Sat 07, 2013 6:39 pm 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4025
Location: Sunnyvale CA
xrhonda91 wrote:
Guess an Isopropyl alcohol "bath" is forthcoming !

More later---stay tuned...


I think the housing is bakelite, so you can use something a little tougher the IPA. Something in the mineral spirits genre might have more effect on the oil - like WD-40.

I predict this will be working very shortly.

Brett


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Sun 08, 2013 5:17 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Thanks Brett, but already completed cleaning earlier...

After scrubbing out the oily "sludge" with toothbrush & alcohol (toothbrush was almost full of brown "crud" afterward !), carefully removed contacts and "sloshed" them around in acetone. Then scrubbed housing again with straight dishwashing detergent and couple drops of water to remove oily residue. Carefully cleaned actuator using Q-tip & "patch" of cotton cloth with alcohol. Also gave pot a liberal "dose" of De-Oxit Faderlube and "worked" wiper... And desoldered electrolytics for replacement.

Still need to remove front grille/bezel from case to clean & polish chrome as well as clean case & knobs before reassembly...

Hope to post pics & get it back together tomorrow...

John


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Sun 08, 2013 11:49 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Bad news---ARGHH !!!

After getting switch issue corrected, found that the resistive element of pot is broken at low end !!!

Now have two "modified" pot projects to do---one for the Royal 475 "flood victim" and one for this set... And gotta find a very low-current coil reed relay to install in switch circuit for this radio because of split power supply...

Went ahead and cleaned the "externals"---Mother's Chrome Polish did a good job shining the bezel edges, but there still is some minor pitting... Nicotine & some clear coats don't get along, and the knob brights had staining that wouldn't come off, so tried Novus-2 very gently---unfortunately it stripped the coating and got the aluminum so had to polish it to make it look decent... Took quite awhile to clean the somewhat fragile Permawear case using just a damp cloth and toothbrush---used fingernail to gently rub off several paint specks.

Here are a couple pics---notice the switch pieces in lower right corner:


Attachments:
ARF 705 PRTS IN.jpg
ARF 705 PRTS IN.jpg [ 222.41 KiB | Viewed 3384 times ]
ARF 705 PRTS OUT.jpg
ARF 705 PRTS OUT.jpg [ 200.08 KiB | Viewed 3384 times ]
Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Mon 09, 2013 12:05 am 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4002
Location: Richmond, VA
Too bad about the pot, but nice job on the cleaning. Looking good!

_________________
Ed


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Mon 09, 2013 1:05 am 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4025
Location: Sunnyvale CA
xrhonda91 wrote:
Bad news---ARGHH !!!

After getting switch issue corrected, found that the resistive element of pot is broken at low end !!!


If the resistance element is still in place, just cracked, try mixing up some silver epoxy, and bridging the crack. I have successfully done that on Dynaco PAS3 pots, which are tapped and therefore there are no modern equivalents. It was a lot bigger than this, however. Gonna need a very strong magnifying glass and a tiny needle to apply it, just put the tiniest scratch of epoxy glue you can manage, and then burnish it into the crack.

I would also recommend stabilizing the rest of the resistance element by putting a tiny drop of cyanoacrylate next to the element, and letting it capillary it's way between the element and the phenolic backing.

Your best bet for a replacement, if you don't have a parts radio, are the guys mentioned above. But the idea of using a DPST relay and a SPST switch (presumably, this one:
http://www.mouser.com/ProductDetail/Alp ... bPvf81g%3d

with the old shaft grafted to it) sounds like a winner, too! You will sure get a more reliable volume control pot that way.

Brett


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Mon 09, 2013 2:21 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Thanks Ed !

Brett---looks like the wiper on original Zenith pot won't come off easily and think I'd rather have a reliable new control, even if it involves modification. This is the part I'll be using: http://www.mouser.com/ProductDetail/Bou ... qCn7SRxdRu I've used a couple already in Toshiba made Philco sets and they seem to be a well made part. Recently ordered several more since they are becoming obsolete. But guess the one you linked to is very similar...

I've already got both Zenith shafts along with a new Bourns control in a baggie to take to work tomorrow. Hoping the guy who runs our milling machine will mill the brass shafts to a precise, centered flat which will engage the "split" in new pot snugly. Then one idea is to put a small collar with setscrew on outside of new control's shaft to retain it securely...

Will post pics when this "comes together"...

John


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Mon 09, 2013 7:19 pm 
Member
User avatar

Joined: Aug Tue 17, 2010 7:15 pm
Posts: 53
Location: Cape Cod, MA
That's the first radio I've seen with the controls on the left. Is it something I've just never noticed before?

_________________
George


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Tue 10, 2013 12:55 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Hello George,

From what I've seen, the first Zenith transistor set with the left hand controls was the Royal 450 which was introduced in 1958 (the Royal 900 "Cordless" also had them), then the Royal 475 (which is an excellent set with a tuned RF amp stage), followed by the electrically similar Royal 490, 705, 66, 68, 73, and possibly others that someone may jump in and add... So they have been around awhile... But honestly, you don't see many around... Think there may be a few other "lefty's" by other companies, also...

John


Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Sun 15, 2013 2:57 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5316
Location: Indianapolis, IN
Hello All,

Made some progress on this set today... After shortening shafts of new pots for both this and the "flood victim" Royal 475, got both installed and wired today. Had to bend solder terminals on both and rotate body of this one slightly because of clearance issues... Simply cut shafts off of both original controls since the milling idea was "killed"... Also had to cut a new slot for "locator tab" since its position was different on new control---after carefully marking new position on PCB, used drill bit just larger than tab in a pin-vise to hand drill at both ends of mark and cut between with X-Acto knife.

Now need to figure a good/relatively easy way to couple the shafts ! Was originally going to mill/file end of original shaft (after cutting to required length) to thickness required to snugly fit into "split" of new controls' shaft and glue, but am now thinking of using bushings drilled for set-screws to make a coupler---this would be more sturdy and ensure better alignment... Just need to figure hardware needed and what's available...

Ordered new caps last week, so hope to get recapping done soon... Also need to find a low-current coil reed relay for supply "tap" switching. The ones we use at work pull 10 mA and would like to get current below 5 mA if possible---just need to investigate whats available on-line.

Below are a few pics---control "prep", "locator slot" detail, and completed "wiring" side...


Attachments:
ARF 705 NEW POT.jpg
ARF 705 NEW POT.jpg [ 205.5 KiB | Viewed 3295 times ]
ARF 705 LOC TAB SLOT.jpg
ARF 705 LOC TAB SLOT.jpg [ 209.02 KiB | Viewed 3295 times ]
ARF FV 475 705 POT MOD PREP.jpg
ARF FV 475 705 POT MOD PREP.jpg [ 186.21 KiB | Viewed 3295 times ]
Top
 Profile  
 
 Post subject: Re: Zenith Royal 705 "project"...
PostPosted: Dec Sun 15, 2013 5:32 am 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4025
Location: Sunnyvale CA
xrhonda91 wrote:
Now need to figure a good/relatively easy way to couple the shafts ! Was originally going to mill/file end of original shaft (after cutting to required length) to thickness required to snugly fit into "split" of new controls' shaft and glue, but am now thinking of using bushings drilled for set-screws to make a coupler---this would be more sturdy and ensure better alignment... Just need to figure hardware needed and what's available....


I used brass tubing of the correct ID (3/16 in this case), turned the new pot shaft down to 3/16, and used J-B weld. Like this:

viewtopic.php?f=4&t=205397

You can get the various sizes of tubing needed at most any hobby shop, in a display rack, from K&S. I have replaced several of them with this style shaft, and one with an extended splined shaft, and it's still holding together.

Brett


Top
 Profile  
 
Post New Topic Post Reply  [ 46 posts ]  Moderator: Dave Doughty Go to page 1, 2, 3  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 5 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB