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 Post subject: Early Zenith Royal 500 "A" project---making progress !
PostPosted: Jul Thu 08, 2021 11:46 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
Hello All,

Had been looking for one of these in decent, restoreable condition within my very frugal budget for a long while to "complete" (other than the very scarce "AB") the Zenith Royal 500 sub-collection. Missed a couple very good deals on-line by hesitating too long. This one was listed on Facebook for a long while with no interest possibly because of the obvious corrosion on kickstand and lack of detail pictures. Recently obtained a '58 Olds Trans-Portable that came from Delco Radio engineering long ago and had been used by a retired engineer. Nice condition with battery compartment that still looked new. It worked at very low volume and needed electrolytic caps replaced. Since I already had a few of these Trans-Portables that I'd refurbished for collection, decided to offer it in trade after seller sent several more pics showing that the volume & tuning graphics were good and that this was one of the earliest models with all black Sylvania transistors and the deal was accepted.

When I received radio, was very disgusted & angry when I discovered that battery leakage damage was far worse than I could tell from pictures. The upper cabinet screw was seized into standoff (it threaded off of chassis mounting screw). When I removed speaker, "chunks" of crud & debris fell out of chassis. A large area on back-side of speaker was badly corroded and covered with residue which I carefully cleaned off the best I could thinking falsely it still might be usable. Even though seller checked speaker with meter, the flex-wires were green with corrosion and crumbled when touched as did cone surface around connection. What was left of the speaker mounting spacer had to be scraped off of magnet support. Audio output transformer was saturated with the leakage and ruined---literally fell apart when removed and handled. You could see the green corrosion clearly below the crumbling winding tape... The small terminal strip for the ferrite-bar output winding return connection was swollen from the leakage and crumbled into powder when touched with screwdriver. The insulated sleeving on several components was also ruined and came off as sticky "goo" during careful detail cleaning of chassis with Q-tips & Windex.

The chassis appears to be tin-plated steel, NOT aluminum as is stated by several others found on-line. A magnet is attracted to it and the plating is shiny and easily solderable.

From what I can find, this is one of the earliest models---the "black dot" version. Circuit matches the earliest schematic with the earphone jack in the audio-driver stage as well as using all early black Sylvania transistors as mentioned previously. None of the engineering updates mentioned in factory service manual have been performed. The S/N is 15481. Ink-stamped date of 2-8-56 on tuning condenser.

Detail cleaned & polished the "cosmetics" first. The cabinet had a lot of scuffs and scrapes, especially on back. Went over it many times with Novus-2 to bring back as much uniform shine as possible. After cleaning, noticed that there were still several granules of sand around grille surround that wouldn't come out---had to disassemble to remove them. While apart, removed small dent in speaker grille by carefully using flat end of X-Acto knife handle to work it out against smooth Formica surfaced table.

The knobs were very dull after cleaning, so went over them several times using Novus-2 and Q-tips and removed residue between grooves with clean toothbrush. Never use any detergents or soaps containing alcohols or solvents as they can attack the plastic ! Was thinking of painting the "arrows" on knobs white, but these just have outlines shallowly engraved at ends of "crossbars". Did they use two different styles on these early sets ? Have seen pictures of some which did have small white pointers... Also surprised to find that there were fiber washers beneath knobs...

Was very surprised and thankful that kickstand and Zenith "crest" were made out of solid brass ! Kickstand had several areas of crusty corrosion and cleaned up very well using fine Scotchbrite and soap solution (and a lot of effort !). Crest was completely discolored by oxidation and also turned out beautifully by cleaning gently with stainless-steel "toothbrush" under running water, then again with brass-bristled "toothbrush" in stream of water to remove fine scratches. Went over both with Mothers California Gold carnauba automotive wax to protect and shine...

Back to the chassis...

Battery leakage disintegrated plating on battery contacts but left metal beneath in perfect condition ! Wonder about the chemical make-up of battery electrolyte ??? Compartment cleaned up very well, thankfully...

There was no battery label (probably due to leakage damage) and what was left of the "battery installation" graphics painted on compartment divider panel was ruined and simply rubbed off... Removed and cleaned more residue beneath. Fortunately, a collector friend of mine had digitally restored his and sent me the hi-res image files to print replacements.

The earphone jack was also a victim of the battery leakage and had to remove it for needed attention---spent around an hour cleaning and refurbishing. Removed the corrosion on nut and threads with stainless-steel "toothbrush" and Windex. Worked very small pieces of fine Scotchbrite saturated with Windex inside the "barrel" and twisted around to remove residue. Used regular toothbrush on contact side as it amazingly wasn't too bad. The switching contact had high resistance and had to clean with 2000-grit sandpaper. Afterward, applied tiny amount of DeOxit Gold liquid and let sit a couple hours then removed excess with thin strips of paper passed between contact surfaces with earphone plug inserted---connection now fine.


Yet another "victim" of the leakage was the mixer transistor socket. Fortunately, the transistor leads were fine and just needed very careful scraping with edge of screwdriver to remove residue. The socket contacts were somewhat "crusty" though and spent a long while carefully applying Windex into holes with plastic fork tang and gently & repetitively inserting/removing a gold plated transistor lead clipping into each. Afterward, used a short piece of tubing attached to vacuum cleaner to remove residue. Repeating this whole process many times, then applied tiny amount of DeOxit Gold liquid into each contact. Fortunately, the contact elements still seemed physically stable and had tension when complete.

Removed all transistors and carefully detail cleaned both sides of chassis after majority of residue removed. The black paint on these early Sylvania transistors is fragile and unfortunately chipped some at top edges during removal even though I had tape on tips of hemostats used for the task. Carefully touched up these areas with semi-flat black enamel using small strips of paper cut into narrow "V"'s. Noticed the two-digit date codes---a couple are "54" and others "61". Couldn't find info on-line, but am guessing that "54" is the 4th quarter of 1955 and "61", the 1st quarter of 1956 ??? Only thing that made sense to me based on the probable manufacturing date...

Replaced all electrolytics carefully forming leads for neat fit and covered with black Teflon insulation. Made support for the now loose (due to battery leakage destroyed terminal strip) battery contact rivets out of a couple small pieces of sturdy, flexible plastic which together were of the needed thickness. Measured and cut slots at proper positions and used jeweler's rat-tail file to round out ends for snug fit.

Since the audio output transformer and speaker were ruined by the battery leakage and replacements not yet found, installed all but the push-pull audio output transistors after cleaning leads again with isopropyl alcohol being very careful around the paint. Since the battery contact plating was destroyed by leakage, wires that needed to be reattached would not solder to terminals ! Need to research this...

After inspecting wiring once again, applied power using clip-leads with headphones connected to the output of audio driver transformer. Turned radio on and volume up full. A few local stations were heard while tuning with some scratchiness at lower half of dial. Carefully removed tuning condenser rotor contact, cleaned, and applied DeOxit Gold liquid to points of contact. The 2nd IFT core was very tight due to wax and one side of slot broke off during adjustment. Very slowly & carefully turned it out with what groove was left and discovered that it was also thankfully slotted on other end as hoped ! Removed hardened wax from threads and reinstalled. All IFT's peaked well and stations were now received more loudly. Adjusting the antenna trimmer further improved performance, but still only received stronger signals. Will perform full alignment once radio complete... Was impressed on how good the audio was using the headphones ! And thankful that the volume control was smooth and noise-free...

Am hoping to find an inexpensive "A" or "B" parts set or good audio output transformer and speaker to complete this early set---have put a LOT of effort into it so far !

John


Attachments:
1ARF 500A SELLER PIC INS BEF 7-7-21.jpg
1ARF 500A SELLER PIC INS BEF 7-7-21.jpg [ 372.44 KiB | Viewed 555 times ]
1b ARF 500A SELLER PIC BK BEF 7-7-21.jpg
1b ARF 500A SELLER PIC BK BEF 7-7-21.jpg [ 74.16 KiB | Viewed 555 times ]
2ARF 500A SPKR DAMAGE 7-7-21.jpg
2ARF 500A SPKR DAMAGE 7-7-21.jpg [ 637.39 KiB | Viewed 555 times ]
3ARF 500A PRTS CLN INS 7-7-21.jpg
3ARF 500A PRTS CLN INS 7-7-21.jpg [ 596.05 KiB | Viewed 555 times ]
4ARF 500A PRTS CLN OUT 7-7-21.jpg
4ARF 500A PRTS CLN OUT 7-7-21.jpg [ 613.86 KiB | Viewed 555 times ]
5ARF 500A GRILLE PRTS OUT CLN2 7-7-21.jpg
5ARF 500A GRILLE PRTS OUT CLN2 7-7-21.jpg [ 776.94 KiB | Viewed 555 times ]
6ARF 500A GRILLE PRTS OUT CLN1 7-7-21.jpg
6ARF 500A GRILLE PRTS OUT CLN1 7-7-21.jpg [ 692.97 KiB | Viewed 555 times ]
7ARF 500A CHS CLN RECAP READY 7-7-21.jpg
7ARF 500A CHS CLN RECAP READY 7-7-21.jpg [ 774.18 KiB | Viewed 555 times ]
8ARF 500A CHS CLN TOP 7-7-21.jpg
8ARF 500A CHS CLN TOP 7-7-21.jpg [ 594.47 KiB | Viewed 555 times ]
9ARF 500A RIVETS SUPPORTS 7-8-21.jpg
9ARF 500A RIVETS SUPPORTS 7-8-21.jpg [ 453.49 KiB | Viewed 555 times ]


Last edited by xrhonda91 on Jul Sat 24, 2021 12:18 am, edited 1 time in total.
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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Thu 08, 2021 11:47 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
More pics...


Attachments:
10ARF 500A RIVETS SUPPORTS INSTLD 7-8-21.jpg
10ARF 500A RIVETS SUPPORTS INSTLD 7-8-21.jpg [ 644.99 KiB | Viewed 554 times ]
ARF 500A SYLVANIA TRANS1 7-8-21.jpg
ARF 500A SYLVANIA TRANS1 7-8-21.jpg [ 450.35 KiB | Viewed 554 times ]
ARF 500A SYLVANIA TRANS2 7-8-21.jpg
ARF 500A SYLVANIA TRANS2 7-8-21.jpg [ 536.73 KiB | Viewed 554 times ]
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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 09, 2021 1:15 am 
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Joined: Aug Sat 16, 2014 2:19 am
Posts: 1963
Location: Palos Verdes, CA
John - Sorry to hear that your Zenith 500 7XT40 needs some parts. I have a 7XT40Z1, serial number 64700, and the chassis is made out of aluminum. I also sent you a PM. - Mark


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 09, 2021 2:03 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
Hey Mark, have you tried a magnet with your chassis ? Are there any solder connections to it ?

John


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 09, 2021 2:27 am 
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Joined: Aug Sat 16, 2014 2:19 am
Posts: 1963
Location: Palos Verdes, CA
John - I took my Zenith 500 7XT40Z1 apart and using a magnet, the chassis is made out of aluminum, although there is solder on the chassis where the coil on the left side of the radio is located, just like the one you own. - Mark


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 09, 2021 4:56 pm 
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Joined: Aug Wed 26, 2009 1:50 am
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Location: Mesquite NV 89027 (from Coventry, UK)
Hey John, sorry to hear that the radio was much worse than expected. They say that a picture is worth a thousand words, but in my experience a carefully composed photo can hide a lot of flaws. In any case, I know that your patience and tenacity will result in this radio being restored to as high a level as possible, given what you started with.


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 09, 2021 10:55 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
Unfortunately, the internal pictures I asked for were small, somewhat dark and not well focused so I couldn't clearly see everything that was shown. The radio is basically done except for audio-output transformer and speaker which I hope I'll find soon. Also, some of the battery box wiring broke off and solder will not adhere to the metal which was beneath original plating that was destroyed by leakage. Looks like some type of nickel or chrome alloy, but have no idea of its actual composition. After reading old posts of Brett Buck's mentioning a flux called "Nokorode" and looking it up on-line, it appeared to be similar to some of the paste flux used for plumbing. After carefully masking off the entire chassis around two of the clean terminals with paper and tape to prevent any splatter contaminating the electronics, tried a tiny speck of high-quality tinning type plumbing flux with iron turned up high---absolutely no help...

Forgot to mention earlier that the cabinet back sides were "warped" inward by the tension of kickstand. Cut a piece of stiff cardboard slightly longer than correct width of cabinet and while gently spreading sides, placed it centered between kickstand holes. Then used hairdryer in "high" setting to warm the nylon by "sweeping" it back & forth a couple inches away for a couple minutes. Had to go through this a couple times to bring it back to normal. Had tried this type of technique (using hands instead of cardboard) previously on a 500D and it worked then also. Before reinstalling the brass kickstand, bent the "legs" outward evenly & slightly so that there was just enough tension to hold it in place securely.

Took a quick pic of the defective parts before bagging/labeling them for storage. Like how Zenith put their name on these early units.


Attachments:
ARF 500A BAD PRTS 7-9-21.jpg
ARF 500A BAD PRTS 7-9-21.jpg [ 588.45 KiB | Viewed 484 times ]
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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 09, 2021 11:21 pm 
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Joined: Mar Thu 04, 2021 2:18 am
Posts: 384
Location: New Hampshire
John,

Is the transformer that's bad on the metal chassis?

Meaning is it the one I see in this picture? download/file.php?id=364804&mode=view

Also, think they used the same transformer in the B model?

I have a friend who is big into zenith sets and I may be able to get you at least a speaker later this month.
I will at least ask.


Henry


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 09, 2021 11:36 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
Thanks Henry,

The "B" set parts would fit and work fine. The audio-output transformer is the one underneath the center divider in the plastic battery compartment.

John


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Sun 11, 2021 12:07 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
Hello All,

Since I haven't heard anything back about a replacement speaker & transformer, decided to reassemble radio to get the parts off of the worktable and bench. Does look MUCH better than it did previously, but will wait until completion before posting final pictures... Placed it first in line on top shelf in cabinet with sliding glassed doors above worktable where the Royal 500 collection along with a few other Zenith transistor sets are displayed. There's also an opening for an "E", so am going to take the earliest of the two ugly sets I've had since childhood and refurbish it the best I can without destroying any more of the original graphics...

Will post further progress when it occurs !

John


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 16, 2021 3:07 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
Hello All,

Remembered that Ken G. long ago sent me a small package of replacement cones for Royal 500 speakers and thought I'd at least give it a try for the very first time. When I removed old cone, discovered that the battery leakage had also wicked into the voice-coil form and it crumbled when touched. The "spider" was also ruined. So this speaker is definitely beyond saving !

John


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Tue 20, 2021 10:55 pm 
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Joined: May Sun 06, 2007 2:52 am
Posts: 2784
If there's anyone on the face of the Earth with the patience to fix that thing,it's you.You did some repair work on a Sears Com-Trek V-which says a lot.

I looked for one of those Sears radios for years(had one as a kid),found one that I was told worked perfectly-and of course it didn't.I couldn't even figure out how to get the chassis apart to work on it.I gave up and threw it away.My search continues.


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Wed 21, 2021 12:11 am 
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Joined: Aug Sat 16, 2014 2:19 am
Posts: 1963
Location: Palos Verdes, CA
John - The Zenith Royal 500 7XT40 uses the same part number 49-788 2 3/4" speaker as used in the 7ZT40Z. I have a Zenith 500 Long Distance and it has a different speaker. When you re-assemble the Zenith 500, you can't see the speaker and you might consider using one from another parts radio. - Mark


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Thu 22, 2021 1:25 am 
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Joined: May Tue 05, 2009 10:21 pm
Posts: 434
Location: Princeton, NJ 08540
Hi John,

It definitely looks much better after you spent so many hours cleaning it up. I wish that I was as patient
as you are. Hopefully you will find a transformer and speaker for it.

Best of luck with your project.

Frank


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 Post subject: Re: Early Zenith Royal 500 "A" project---frustrating...
PostPosted: Jul Fri 23, 2021 11:52 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6962
Location: Indianapolis, IN
Thanks much, Guys !

Mike C.---you should have posted and asked for help on the Comtrek ! That one wasn't fun, but worth the effort.. Too bad you threw it away...

Been busy on several fronts here, so am going to try and put together and post the "progress report" with pictures for this historic radio soon.

John


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 Post subject: Re: Early Zenith Royal 500 "A" project---making progress !
PostPosted: Jul Sat 24, 2021 1:07 am 
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Joined: Jan Thu 01, 1970 1:00 am
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As usual outstanding work!!!

You may already know, code on speaker is 285603, 285=Rola, 603 1956 week 03.

That'd play into the date codes you suspect on transistors.

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Tom


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 Post subject: Re: Early Zenith Royal 500 "A" project---making progress !
PostPosted: Jul Sat 24, 2021 2:55 am 
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Joined: Oct Mon 26, 2009 10:02 pm
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Location: Indianapolis, IN
Thanks for decoding the speaker number, Tom---had no idea ! The ink-stamped date on tuning cap is 2-8-56.

John


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 Post subject: Re: Early Zenith Royal 500 "A" project---making progress !
PostPosted: Jul Sat 24, 2021 4:44 am 
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xrhonda91 wrote:
Thanks for decoding the speaker number, Tom---had no idea ! The ink-stamped date on tuning cap is 2-8-56.

John

Assuming there is a mfgr/date code stamp in the metal, ink stamp date is probably day radio was built.

A stamp of 273602 would indicate Radio Condenser Co(common supplier), & 2nd week '56. By mid '50s, most mfgr were transitioning to a four digit code for date, 2735602 would be same code.

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Tom


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