Zenith 8-5-463 black dial console. Didn't need; couldn't resist!
 

My wife texted me last weekend that she saw this radio, but for whatever reason my "old" flip phone wouldn't take the media message with pictures. So I went on dusty, but shines under the dust. Tubes there; speaker there, and the dial is black. $50 firm was the price. I couldn't see how I could go wrong except for the guilt and pain felt of bringing something else into the house.

The interesting part is that the radio was found but never tried out due to a bad cord. I liked the sound of that myself. When it made it to my place the first thing I see is a section of maybe drop cord with a modern 3 prong replacement plug end. Hmmm. Never tried it out....:scratch2: The older lady's story was that it needed rewiring. I thought it as layman's vernacular. But I have read some Internet posts on Zenith radios of this vintage having bad rubber insulation and some actually having to be rewired. I hope its not that bad when I pull the ultra dusty chassis. It looks from the top as if there is both cloth and rubber wire insulation and the cloth is nice; some of the rubber is nice, and some is gone like coming out of IF cans to grid caps.

The cabinet looks like it will come back to be beautiful. The slats over the speaker cloth are all good (read to be a problem). So it's the typical clean and cap deal I imagine. I may even get lucky and have the thing work as is. I have many table models of that era that work great as is. Being such a potentially nice piece, I want to at least go through the power supply with the darned 6X5 rectifRIER. The picture is just reference. Not mine.

Take it from me: the rubber can look fine and be brittle and missing tiny chips in critacal places causing shorts.

I just got a chair-side with that chassis for $25....It only needs a refinish, new dial glass scale and pointer, the preset button escutcheon, and a full electrical resto...

Nice radio, but 40, 41, and 42 is when Zenith took a slight dip down on the quality. 6X5 recifiers, rubber wiring, and in 42, very cheap tube sockets. Had 'em break on me real bad before. That was for the Loktals, this set has mostly octals, so you're fine on that. You'll want to convert it to solid state rectification. Those 6X5's are a ticking time bomb. Had one short on me one time, thank God I was there to catch it before it took out the transformer. This is a 40 model BTW. The 4 in 463 means 40. 5 would be 41 and 6 would be 42.

OK, so it seems that I didn't do too badly, but my work is cut out for me. Indeed there is only one loctal tube and it's a goner at about 40% emissions. I really appreciate that drawing TUD1. If I interpret it right it looks very simple in that you simply wire in the two 1N4007 diodes' anode where the plates would be; eliminating them (plates) from the circuit. On the other end it's solid state diode cathode to chassis ground. The heater string resistance is in the left in circuit tube for originality.

If I have that right I may just do that on this set and an evidently pretty rare Silvertone set that I have with the 6X5. It's a 4663 model and IF I find them they are super pricey by my standards. I don't know if that says a lot, but I sure don't want to fry it. My beloved Hickok 209 VTVMs use them as well.

Thanks all for chiming in. I see I'm not in this alone as Electronic M is on board. A good man to have beside ya in a radio/tv foxhole!

Is that all it needs! :D

God only knows, since I haven't opened it up (or powered it) yet. It is missing a couple of tone buttons, and the speaker cone is damaged too...Maybe I should have left it at Goodwill... I can't start work on it for a while. I've still got a Philco cathedral and a 13" color Zenith to fix for paying customers, and some half completed TVs of my own that I paused for the paying work.

I've got an upright console with the same control panel (and presumably chassis) that was built for 25Hz power. The darn thing still worked nicely on original parts, but I recapped it anyway.

I haven't seen anything at a G/W store, that even resembles an old radio.
The last G/W, I went to, didn't even have VHS tapes. They must've quit handling them. :thumbsdn:

It's probably the 3rd to 5th pre-HiFi tube set I've got at thrifts in the last ~8 years, and that don't count tube HiFi gear and stuff they wanted WAY too much for.

I got the guts of a late 50's/early 60's stereo RCA at the same place and time as well as an LG flatscreen monitor*. The cabinet was ugly and I could not fit it so I field stripped the thing and re-donated the cabinet. :D

*It would come on to it's welcome screen and die a moment later. It was the first flat screen I've fixed. One of the lytics went, and changing it fixed it, but somehow it is now in Japanese language mode....At least I can read enough Japanese to operate it.

I made a mistake on my entry. They had one of those lousy repro cathedrals, either a Crosley or a Thomas. Some rediculous price, $12.00 or $15.00. I wouldn't pay 10% of that. :thumbsdn:

Tubejunke, this may have just been "a slip of the pen," but feel that I have to point it out just to be sure: with reference to replacing the 6X5 with diodes, you wrote:

If I interpret it right it looks very simple in that you simply wire in the two 1N4007 diodes' anode where the plates would be; eliminating them (plates) from the circuit. On the other end it's solid state diode cathode to chassis ground. The heater string resistance is in the left in circuit tube for originality.

Note that the cathodes of the diodes don't go to chassis ground (which would represent a dead short!) They go to the field coil and the + end of the first filter cap.

As to the 6X5 heater, yes, it can be left connected for show, but disconnecting it would give the sometimes feverish Zenith power xfrmr a bit of a break!

Tubejunke:
Now what I've heard though is that the 6X5GTs are safe tubes to use in these circuits as they aren't as suseptible to dead shorting, whereas the 6X5G or the 6X5 (metal cased tube) are the ones you have to watch out for. So if you have some 6X5GTs in that radio or can get a hold of some NOS 6X5GTs then you should be able to still use the tube rectifier circuit in this radio yet without having to worry about frying your Power Transformer.

Everything you need to know about the 6X5. In contrast to ordinary filament-type full-wave rectifiers, the 6X5 is one of a family of heater-cathode full-wave rectifiers. Unlike some large members of the family, there is no connection between heater and cathode in the 6X5 family. Apart from filament/heater burnout, any vacuum rectifier tube has two major vulnerabilities. One is excessive peak inverse voltage, and the other, excessive peak plate current. Both may cause arcs and shorts in any vacuum rectifier.Heater-cathode rectifiers like the 6X5, with no connection between heater and cathode, have a third vulnerability, which is heater-cathode voltage at or near redline. No heater-cathode potential can appear unless the heater is referenced to ground, or worse yet, operated at ground potential (the cathode carries the full B+ potential above ground). Unfortunately, this is the case in almost every application of the 6X5, as it is operated on the heater circuit carrying all the other tubes, a circuit almost invariably tied to ground in one way or another.
The alternative, of course, is a separate rectifier filament winding that could be "floated" without reference to ground, but that separate winding is what designers were trying to get away from in the first place... It was common, unfortunately, for designers to redline many parts (especially tubes) to get the most "bang" out of their products for their invested buck. With the 6X5 being operated at redline (or beyond) in certain radios, there were a lot of bangs. When you redline any tube, you are simply asking for trouble. Redline output and rectifier tubes, and you're asking for BIG trouble. The 6X5 was apparently pushed to redline on heater-cathode potential and/or peak plate current in sets where it is notorious for shorting out, but this was a designer's fault, not the fault of the tube itself (it may also be possible that the tube was originally rated beyond its actual ability to stand up to punishment). The 6X5G and GT are at equal risk of developing a short, it's really how the tube is treated in circuit that affects its chance to short out. 6X5's will last a long time if run comfortably within their ratings, and especially on a floating heater winding. If the heater has no reference to ground, the major cause of a heater-cathode short is removed. The only caveat is that the floating heater winding should be able to withstand full B+ potential to ground in case there is such a short.

Thanks for correcting me on this Reece. I really don't know what propelled me to say that except to say that I had been working on an old Zenith "roundie" color tv that I have and I have been watching cathode current on the horizontal output tube. To do that I break the grounded cathode to place an ammeter in series. No excuse really for mixing that up with a rectifier in a power supply. Geez!:scratch2:

Anyway, I have a couple of 6X5GT tubes that I can use for the time being under close watch in these early stages of resurrection. Swizzyman gave a great read on these bad rep tubes. I hope Captain Clock read his post and I can attest to the GTs shorting as the tube that came in this Zenith was a GT with low emissions. I scavenged a couple of other GTs that I had sitting in boxes and threw them in my trusty old Sylvania 140 tester. One was fine and is in the now playing radio. The other gave a sharp flash when I plugged it in and the neon short lamp went full on. Good thing to have a few old tube testers around!:yes::yes:

So yes folks this old Zenith radio came to life last night with little more than a dusting out, a rectifier tube and pin cleaning on only a few of the other tubes. The story's not over though. The volume is pretty low; the tuning eye looks completely dead, and all of that neat O Zenith tuning presets or whatnot has to be cleaned and lubed. I'm assuming that they are station presets. The closest thing I have seen to what I see there is in my Transoceanic radios and they are band switches.

On one side the buttons are broadcast presets (there should be a band switch position "automatic" IIRC for them separate from the broadcast dial tuning position) and the buttons on the other side (left) should be the tone switches.

I once had a Philco 6X5GT short out and nearly destroyed the transformer. I caught it just in time.

The pushbuttons could well be station presets, as were (and still are) used on car radios. These presets were on one side of the radio dial in the Zenith sets; the buttons on the other side were for a tone control arrangement Zenith called, IIRC, the "Radiorgan". Some Zenith tabletop sets had the presets in a horizontal row just beneath the tuning dial. I seem to remember one such radio that did have the presets in this position.

BTW, I am fairly sure the model number of the Zenith radio being discussed here is 8-S-463, not 8-5-463.

Lousy? Don't sell those replica sets short; some of them may be junk, but others might well be excellent performers. I have one, a replica of a 1934 cathedral radio, that works and sounds great. The only thing I can't figure out is why the FM tuning scale is so spread out on mine, as it uses a simple plastic tuning capacitor for AM and FM tuning, not a varactor or slug-tuned tuning system. Regardless, this radio works excellently, even in this semi-fringe area 40 miles away from most Cleveland FM stations. The wire FM antenna came disconnected from the radio somehow, but the set still works, bringing in every local FM station. The sound is great, owing to the 4-5" round speaker with a large magnet and a wood cabinet. I think I only paid $20 or so for this set at a discount store in my hometown. One of the speaker leads came loose from the PC board chassis, but I can fix that in five minutes flat; in fact, I am sure that is all that's standing between me and a really good sounding radio (for what it is).

I know my Zenith C-845, K-731 and Royal 3000-1 will run rings around it as far as sound quality goes, but as I said, for what it is, my little replica cathedral set doesn't sound half bad. It even gets a station my other radios don't get at all: a classical music station right next to (on the dial) a powerful country-western station about eight miles from me. The classical station is on 104.9, while the country station is 0.2 MHz down the dial at 104.7. This radio has full-time AFC, which one would think would pull the tuning toward the strong station, but on my little set it doesn't seem to work that way. :scratch2:

The only replica set, that impressed me was the GE model, but they were rather pricey, but received and sounded great
The styling is genuine RCA-GE of the early to mid-40's. They might've been made at the same far-east plant as the Superadios. :thmbsp:

Well, since I was actually pulling in stations with little trouble I thought that I would yank the 6U5 "magic eye" which appeared to be dead. I've seen them all varieties of dim, but never completely dark.

The old thing is a little tough to pull, so I give it a good pull and the tube comes out and the socket falls apart in my hand. Nothing looks broken though. It wasn't hard to pull up a fair amount of material on the WWW concerning getting the thing wired back in correctly. This may be a good thing as the 1 Meg resistor I have read about revealed it's self and remains to be checked. At the same time it will help me in reconfiguring the socket. The two large pins are heater pins (1 & 6). The resistor jumps across pins 2 & 4 to B+. Pin 5 should be a wire that is a ground for the cathode and the only one left will be pin 3 for the grid. Not a problem.

The old Sylvania 140 proved that the tube was indeed dark as they come. So I got a short lesson in the fascinating world of the magic eye, which is deemed a cathode ray tube of sorts; a chance to check out the known problematic resistor, and weeded out another bad tube. I sort of hated tossing the old original script Zenith tube, but bad is just bad. On to yanking the chassis for a good cleaning a bit of wire replacement and likely power supply electrolytics. There is only minimal hum in the set and I can't tell yet if they run warm, but with what seems to be a delicate and slightly undersized power supply I don't want to take any chances. Later I may do the 1N4007 solid state rectifier job once I have worked other things out. Oh and there is a rubber or leather strap or band that controls the tuning. I have seen one online and it looks to me like an o ring with a hefty price. If that is all it is, I imagine I can size up something that will work for a few bucks.

Always keep the bases of fat pin tubes. You never know when you will need one.

Just so everyone knows it was actually someone on here that told me that the "GT" version of the 6X5 tube was actually a good tube to use in such circuits because they were less suseptible to shorting than the 6X5G was, and I actually have an old 1940s Philco Console that uses a 6X5GT as a rectifier and although I haven't had a chance to power it up yet because it had a mouse nest in it and the mice chewed through some of the wiring in the radio, I'm apted to believe that what that person said about the 6X5GT is true. By the way, from what I heard from this person is that there were two different grid arrangements for the 6X5 tube and the 6X5G tube and some of the early 6X5GTs used an "X" shaped grid (think of the later 6X4 or the 6CA4 which were the later replacements of the 6X5 tube), but then later on once tube manufacturers realized the fatal flaw of the 6X5 tube they redesigned the tube (the 6X5GT as the 6X5Gs were no longer being made at that time) so that it had inline grids instead of "X" Shaped Grids which made the tubes more reliable, at least until the 6X4 and the 6CA4 came out to replace the 6X5GT tube.

Did that 6X5GT tube have the "X" shaped Grids or did it look like the one in the picture below? I'm asking because the 6X5s that had the "X" shaped grids were the ones that were more suseptible to dead shorting whereas the ones that had the grids that were inline like the one pictured below are less suseptible to dead shorts, that's what I was told anyways.

I've had the flat plate ones short on me in an EICO audio signal generator (both the one in it and it's replacement that tested good before installation, but not after). Never tried the X ones, but I'd assume they were better than the flat plates since the later 6X4 and 6AC4 used and those and were considered more reliable than the 6X5.

I meant RCA-GE styling of the early to mid-30's. :scratch2:

:thmbsp: Of course your correct here , the ones with the "X" shaped plates are the preferred ones to use if your going to use a 6X5 , as you rightly say the 6X4 and 6CA4 being the later model 7 and 9 pin replacement for what was the final improvement of the 6X5 design , the X shaped plates . In that transition they must have done something about improving the heater to cathode insulation , the way I always found the "flat plate" ones to be shorted . The 6Z4 , formerly known as 84 , was the first of these type of dual diodes and it was never pushed very hard with respect to it's H/K breakdown voltage since it was designed for the first vibrator power supply car radios (that replaced dynomotor powered ones in the early 1930s) and these were under 200 volt applications . The 6Z4/84 was the old large 6 pin base used before the Octals came to be , and when the Octals were introduced the 0Z4 was introduced along with them for car radio rectifier service , as we all know it's a Gas filled full wave rectifier that needed no heater at all . The trouble for the 6X5 started , in my opinion , when it was coupled to transformer supplies with 350 or more volts being pushed through a design that originally would have seen barely 200 .....

You guys blow my mind with your incredible knowledge of tubes. Right down to a single tube and improvements after. I love tubes myself and often sit and thumb through my 50s Sylvania tube manual, but I don't know much about design changes and such. Love reading what you all write.

I haven't had time to progress much except for a bit of cosmetic cleaning on my Zenith. I was really surprised that night I had it pulling in stations as that crazy loctal tube reads pretty darned dead on two very good testers I own. Why in the world they would jam a loctal into the compliment is beyond me. Probably to save money. I wish someone could tell me the diameter of the tuning band, strap, or whatever it was that rots away on these. I think I can just use a common o ring to save a buck.