Isee several of these selling on the bay. Some say hand wired ,others not. what do they mean by hand wired. And did they do both or are they all hand wired. ?

Only the earliest used "hand-wired" metal chassis which are much more valuable---then they went to printed circuit boards like most others... There are on-line sites with pics & detailed info---try Googling keywords: Zenith Royal 500 hand wired

Hand-wired simply means that certain components are installed & connected point-to-point by hand beneath a chassis which others are mechanically attached to...

John

There were hand-wired/point-to-point wired versions, and versions with PC boards. The early versions were hand-wired and are collector's items. The later PC-board versions are less valuable, apparently. There are a large number of variants of each kind. I *think* and someone here will certainly know, that all of the hand-wired versions were 7-transistor original model 500s, and they went to PC traces before they went to any 8-transistor versions.

Either of the original 500s was a fantastic advance over most of what was available at the time in terms of performance. But things changed very rapidly, and the later 8-transistor versions like the 500D and E are much better performers and the 500H has the same sort of performance as the D/E and much superior sound quality. The early circuit boards were/are fragile so cracked traces are quite common, particularly on the 500H. I have one 500H that is now a point-to-point wired version - only because just about every trace was cracked and I just ended up jumpering just about everything on there.

Brett

The hand-wired versions were the first, early 7-transistor Royal 500's, then PCB's onward in the "500" series... If site I'm thinking of is still on-line, it will have pics and details...

And I sure know firsthand about the 500H PCB issues...

I got clued into it by someone else. I had gotten a little behind on my projects, so I farmed out a few of them to someone else who knew a lot more about it than I did. When I got it back I found that he had spent an inordinate amount of time for the cost, and I felt pretty guilty about it. I later did a few other 500H and 500e1s myself and few hours in I gave up trying to figure out where it was broken (since they were all intermittent), and just doubled every connection on every trace with some 32 gauge wire-wrap wire (soldered, of course), following the original traces. That worked well, and it got rid of all the horrific factory solder joints, too. Once it was done, I "conformally coated" them with model airplane cement, and now the thing works great and there's no way the jumpers are moving or cracking. IT probably took less time and was more reliable than trying to find all the microscopic cracks and then fixing them, only to have it crack somewhere else.

I *should* have figured this out myself, because I have done dozens of old Dynaco cards that have the same sort of problem, and look like the same absurdly thin copper traces. If you think it's bad in a nice cool-running transistor radio, imagine what it is like inside a little furnace like a Dynaco FM3 or even worse, an SCA-35. The 500e board and earlier have relatively thick traces that appear to be able to survive delaminating from the phenolic, since I have seen them hanging loose but would still function.

Brett

The original Zenith 500's had point to point wiring under the circuit board, and sockets for the Transistors.

They are easily distinguished by the volume and tuning knobs, BTW, as they have a pointer going across the entire dial face.



The later models don't have as bold a dial; also note the difference in the speaker grille...

I questioned someone on eBay about an obvious PCB that he was describing as hand wired. he insisted it was hand wired because he saw a couple of wires connected on the PCB. so it goes depending on who you are dealing with weather it is really hand wired or not. my thought is point-to-point all the way through is considered hand wired not PCB with a couple wired connections to the battery and speaker and such

OK, here is the top of a printed circuit board, later model Zenith 500;



Now just because there are maybe a half dozen wires above it does not give it the distinction of being considered as "hand wired", by collectors.

Now notice that there are actually fewer wires above the board, on the original;


This is what the underside of a non-PCB, hand-wired chassis looks like;

In all honesty, the early Zenith's were all hand assembled & "wired"---including the PCB models...
Would probably be better to say non-PCB, metal chassis, point-to-point component wiring, or ?

Thanks Fifties for that great pic of metal chassis underside !

Here is the link with great Zenith transistor set info: http://www.transistor-repairs.com

My oldest Royal 500 is one of the early PCB models from 1957---bought from a neighbor for $2 some 40 years ago as a kid. Had bad audio coupling cap then...

Thanks again picture work great. now i know I am smarter. LOL

And those early Raytheon transistors on top side---WOW ! Great set !

I am sure you know this, and not that I am suggesting they be changed in your original collectors item radio, but for those who are not aware - the white ceramic electrolytic caps have an absolutely astronomical failure/dry-out rate. The little ones in particular are almost always dead or with such low capacity that they severely degrade the performance.

Brett

edited to correct caption - sorry about the confusion BB

Brett, you're killin' me, lol, by using my upper captioning -referring to the top side of a PCB, with the lowest picture, which displays the underside of an earlier point to point wired chassis, in your quote, thereby thoroughly confooziling things.



Also, I am sure you didn't mean to include the term, "ceramic", in your reference to the paper covered Electrolytics. We know what you mean, but confusing to the newbies.

i think they *are* ceramic. I just took a few out of the discard box, and tried to scrape off any paper, the knife just skidded across them surface, and then I cracked it with a pair of pliers, and they cracked like ceramic. The outer coating is literally rock hard and about 1/32" thick. The versions I checked out are the iei/Nashville brand, and they have the red resin and amberish-looking resin just like those shown above.

Don't mean to be confusing, of course, the quoting error was just a slip of the finger.

Brett

p.s. now, through the miracle of ex-post-facto-editing, it is consistent... BB

p.p.s.

Here is one I cracked open:


The walls are rock-hard white all the way through and cold to the touch. I cracked it open with a pair of pliers, there was no "give" whatsoever, it just cracked. Inside its about what you would expect, foil and condenser paper. This one, not surprisingly, showed not even a hint of ever being wet, which is presumably the problem.

I took one of the shards and broke it up some more:



It is extremely hard but breaks up into a dust eventually. I did several different ones and they were all like this. I am pretty convinced that it is a ceramic tube. It it definitely not a paper wrapper over something else. I suppose it might be paper completely saturated with water-glass but I don't think so.

I also noticed another feature - ALL of them were cracked before I started in on them with the pliers. I didn't notice this before, but ALL had longitudinal cracks - tiny and only noticeable with a magnifier and my glasses off for super-close-up viewing. This is probably the failure mode, once it cracks it dries out, no capacity, no sound.

So, not to be argumentative, but take a few discards and check it out for yourself, I think you will find that the outer tubes are some sort of white ceramic.

Fascinating, as I always *thought* the capacitance rolls of paper and foil were simply covered with a white paper label, but in checking some of mine, you are correct.

I still wouldn't refer to them as ceramic, however, in order to avoid confusion. When I think of a ceramic cap, it's yellow or burnt orange in color, flat and round. And when we ID caps, it's the guts we are mainly talking about, not the cover material, correct?

hard cover paper/foil capacitor

Right, the that's why I was trying to use "white electrolytics" or "white ceramic electrolytics" whenever I mentioned it. I may not have been 100% consistent on that. I noticed that they were hard ceramic because they are almost impossible to pick up using my hemostats - they just squirt out of the jaws.

The other salient fact that the failure rate is approaching 100% at this point! The black plastic types from the same era are much more likely to be good and I have a fair number of radios where I just left them if it seemed to be working properly. I am not a big on shotgun repairs but if it's this type I just ditch them automatically.

Brett

p.s. a followup - here is one of the many of these that exhibit cracks. It is my belief that most of these were cracked at the original installation - I have one that was glued with the brown goop they used to use, and the goop shows evidence of having been liquid when it went near the crack. I would guess that it's a matter of the heat of soldering, and it appears that the cracks tend to start near the red plastic end as opposed to the resin-sealed end. That makes some sense, the plastic will expand and put force on the body, the resin just gets soft and runny.

I also noticed that the few like this that do not not appear cracked still measured close to the marked value. All the cracked ones were dried out and exhibited very low or no capacitance (and no shorts in any of them, BTW).

Ignore the photomicrography of my lacquer-thinner and Exacto-knife scarred fingertips and poor manicure!

Given enough patience, I think someone could restuff these with an SMD electrolytic.
Then attach new leads on both ends and seal with the appropriate colored epoxy.

Eh?

~ Mitch ~

Maybe. I thought that sounded like a simple task and a good idea until I measured the ID of the smallest one (3 mfd/12v) - about .162" . That's a little smaller than a 3 or 4.7 mfd SMD cap, at least those I found in a 30-second search of digi-key. The bigger versions, like the monstrously large 500 mfd/12v, would fit a few modern axial caps of the same capacity. Getting the guts out without destroying the tube might also be an issue, particularly since they are mostly cracked already. i would try gluing up the crack with cyanoacrylate before heating it.

I have a handful or so of them if you want to try it. I don't need them back. I was going to toss them anyway. I also have a bunch of the black plastic types which would also provide the period look if restuffed.

Brett