1941 Zenith 8A02/8S563 Console found
 

I got this at the flea mall today for the princely sum of 75 big ones. I have no idea if it works, the cord is almost non existent. But I wouldn't have tried it anyway. I will be taking it to my local antique radio club this weekend and see what's going on with this thing. They may or may not remember me. The last time I was there was when I got my 1941 Philco 42-327 in September. I have never worked on a Zenith before, any tips or advice is very much appreciated.

Here's the back. For some reason, my i-Phone will only allow one picture per post.

The 6X5 tubes are prone to shorting and taking out the power transformer. Replace them with 1N4007 diodes.

Rotted rubber insulation on wires in this era of Zenith can be tedious to deal with.

I got this radio just in time for BirmingHAMfest 2015. They always have all sorts of tubes and testing equipment. I'll be sure to get the tube names for this radio and check for them at Hamfest.

And put a 1/8A. fast blow fuse in line with the power tranny HV secondary center tap. Perhaps a 1A. Slow blow fuse on the primary.

I have been informed that 8A02 is the chassis no. and 8S563 is the cabinet no.

Do NOT replace the 6X5 power rectifier with ANOTHER TUBE, the 6X5 was a bad design and basically all of them (regardless of brand) are equally DANGEROUS to the power transformers (which are orders of magnitude more expensive and harder to find than the tube). Running one with a 6X5 is like running the set with a time bomb in it.

Just get 2 1N7007 diodes from your local Radio Shack or dealer of choice, remove the cathode and plate leads from the rectifier tube socket (leave the heater attached so it glows and looks original), add a terminal strip nearby under chassis, and attach those leads and the diodes (observing proper polarity).

I'm expeienced in toilets, lights, and vacuum cleaners. But I'm not very experienced in tube radios. I'll have to study the rectifier tube socket and all sorts of stuff before I can do that. Can you explain that just a little bit, please?

Can anyone tell me about small low power AM transmitters? The local AM station that I very much enjoyed is defunct, so now I have nothing to listen to except gospel and jabber-jabber. I hate both. Any ideas how I can play my own music over my antique radios without making the FCC mad?

They make a lot of styles, a friend of mine that had an AM-100 transmitter just bought one of these off ebay, says that it's a TON better than the one he had

http://www.ebay.com/itm/Talking-Hous...item5670c4da30

http://videokarma.org/attachment.php...1&d=1424371651

Label and disconnect the leads on the socket pins K and P in the above diagram. K is the cathode. P are the Anodes (called plates in tube speak).
A 6X5 is 2 diodes in the same bulb with the cathodes connected together.

http://videokarma.org/attachment.php...1&d=1424371651
Above is the symbol for a 1n4007 diode the stripe on the part's body indicates the cathode end. It should not be too hard to figure out the connections from here.

It took me less than 3 minutes on google to find the pictures to make this simple to explain.

I happen to like talk radio when they have something interesting to discuss, but music is also important to enjoyment of such equipment.

TUD, I have that same Zenith and i got it off CL for $60 knowing the transformer was toast due to the 7Y4 tube,just as bad as a 6X5, of course.

It does not list that model number, just that chassis number - Very strange

Mine also has a 6K7 in place of the 1232 as an RF amp

I have a spare chassis (with a good trans) and speaker from a 8S359, also similar but with the evil 6X5.

Just haven't put the two together yet...

TUD if your set uses the 7Y4 google "7Y4 tube data", and look for a PDF of a old tube manual listing of that tube containing a figure similar to the first figure in my last post....The set's schematic will also contain a similar diagram. If you don't have the schematic for your set check a site by the name of 'Nostalgia air' they have many schematics from the rider's manuals.

My Zenith does not make use of a 7Y4. Here is the schematic.

Do you all feel the same way about ALL of the indirectly heated rectifier tubes--like 6AX5, 6CA4, 6X4 , 5AZ4 ?

No. Those later designs were greatly improved and MUCH less prone to the type of failures the 6X5 was infamous for (they learned from their mistakes). Heck if only it would not look like a complete hack job the 6X4 or 6CA4 would probably be decent replacements (with proper socket adaptation) for the 6X5.

Some of the LAST 6X5s supposedly were 6X4s or 6CA4s in an octal envelope, and were as safe as the rest of the later types, but if someone like me who has been doing this for over a decade has a hard time telling the difference, then advising a novice to do so would be a bad move... I don't want to give him advice that could lead to an expensive component (the power transformer) being ruined.

My beloved 1320 AM is back on the air! (For now.) I'm taking advantage of the opportunity to jam with the 1941 Philco 42-327.

THAT is why I told him to put FUSES in the chassis. I did so on my slivertone stereo chassis I recently acquired. a 1.25A. SB on the primary. I feel a 1A SB would work well on that radio chassis in the primary .


I DID have that exact chassis and maybe the speaker--it was GIVEN to me many years back. Think it was STOLEN a couple of years ago in the garage robbery though...

Fuses are fine and dandy, but when you take a NEW 6X5 that tests good and use it to replace a shorted one only to have the NEW GOOD one SHORT in a brilliant LIGHT SHOW the MOMENT it warms up you kind of loose confidence in all tubes of that type. There is a reason Zenith power transformers of that era are harder to find than those of other makes, and I think you can guess it.

You could possibly run that with all the original caps as a daily driver too with just a fuse, but would you REALLY want to do that?

Now let's just calm down... My plan for this weekend is to 1) replace the cord, 2) check/replace all the tubes, 3) replace some capacitors, and 4) completely do away with the 6X5G. If someone can just explain how to physically install the diodes, that would be great. I don't have any desire to keep the old tube just for looks, even the socket will probably go. I am capable of all the rest of those things. Hopefully, I will get this radio working this weekend. Maybe.

I meant to fuse it..>AFTER it it repaired. Duh !!! INCLUDING the wires--Zeniths of that era are known for VERY brittle insulation on chassis wiring.

Ok. In that case---there are a couple of ways to go. One--cut the 2 leads from the trans that feed the 6X5 socket plate pins ,solder the anode of a 1N4007 to them (one on each lead --under shrink wrap if possible,), tie the cathode ends together and solder them to the cathode lead of the socket. This totally eliminates the tube. You could still leave it in this way--since the plates will NOT be in ckt.

or. mount a terminal strip somewhere close to the tube and tie the diodes to it, and run the cathode ends to the cathode of the tube socket.

Okay, that sounds easy!

Speaking of small AM transmitters, I found a system used for real estate called the Talking House. I wonder if I could hook up my i-Phone or something to it and broadcast to my radios? Sounds like it would be ideal to me. I just wanted to get y'all's opinion. Just Google "talking house radio transmitter."

I used, either the latest issue 6X5GT or the later JAN 6X5WGT. I'd like to see that baby short.
I'm rather against using silicon rectifiers in old equipment, unless it was original design. They're a little hard on the electrolytics because they get full or excessive voltage, instantly. You should replace the 'lytics with higher working voltage, than the originals.

I bought one of those "Junior DJ" units at a thrift. I works remarkably well. I stripped all the kiddie stuff off of it and mounted in a project box and equipped it with a whip antenna and an AC adaptor.

The rectifier tube in that was in my Zenith when I got it was a GE Electronic 6X5GT. I'll be doing away with it altogether. I'll also be sure to replace the electrolytics with a higher working voltage.

My Zenith chairside has the same chassis. That chassis uses the direct coupled triode driver and 6AC5 triode output. Why????? most of the other Zeniths used penthodes.
Mine came with, probably the last 6X5GT's made. It has the small internal structure like the 6X4. I'll leave it! :thmbsp:

I cleared out a spot in my bedroom for the new Zenith. I will be putting the Philco on top of the Zenith. After I get the Zenith working reliably, of course.

Should I put a three wire grounded cord on the Zenith or just use a two wire?

It took all morning to get the chassis out if the cabinet. By the time we go it apart, it was time to go. One of the older gentlemen there said I could replace the 6X5 with a 5Y3. If I remember correctly.

The 5Y3 requires a 5V filament supply versus the 6X5 uses 6.3V. Also the current draw may be different? I was not aware that there is a known failure problem using the 6X5GT. Thought that was only with the original 6X5. :scratch2:

The pinout is totally different on the 5Y3 VS the 6X5. Plus the heater voltage.
The last chassis like that, I replaced to PT on, I replaced the 6X5, with a 5Y4, as the socket didn't have all the contacts for the more common 5Y3.
If the transformer has a separate five volt winding for a rectifier tube, I prefer to use a five volt rectifier tube, fully knowing that the six volt rectifier tube isn't that reliable. :thmbsp:

The NOS one that went bad on me was a 6X5GT....

There was a large difference. The 6X5 only draws 600ma, heater current@ 6.3 volts. I was tempted to use a 6AX5, but the heater current is 1.2 amps@ 6.3 amps. The Zenith power transformers were undersized, as it was, without adding to the load. :yes:

I wondered this as well and looked at a book I just got "understanding hi-fi circuits" by Norman Crowhurst. What I took away was this:
The triode output versus the pentode has lower harmonic distortion but the plate efficiency is also much lower, reducing output power. Additionally, the handling of varying plate load, due to output transformer and speaker reactance across the frequency spectrum is improved with the triode. It is likely a tradeoff that Zenith accepted in exchange for better fidelity.

This odd feature of the Zeniths is motivation enough to recap (and replace the tranny) and give it a serious listen.

Tube data sheets show the 6AC5 capable of 3-4 watts, with around 250 or so plate volts...-in SE..which your chassis is.

I went to the workshop this morning and started early on my Zenith. I replaced a few small capacitors, and a 16 MFD 475 volt big capacitor. I checked almost all the tubes and put on a new power cord. I then proceed to "smoke test." So I yell "smoke test!" I powered it up slowly on an isolation transformer, and when I got up to about 50 volts, the current jumped way up. We concluded that the circuit is short. :dammit:

ok...at this point...you need ot see if the power tranny is shorted or not.

With the 6X5 rect out of the ckt and NO diodes in to sub it....( IOW--and OPEN ckt on the HV winding of the tranny), and ALL tubes out of the set...do another variac test. THIS time...you should NOT get much draw--no more than maybe 25 watts or so--likely less--with an open ckt on the transformer. If you DO--then disconnect ALL leads from it-other than the primary--and try again. If it STILL drews over 1 amp or higher--with no laod--the HV winding is shorted. if it then drops to a very low draw...there is SOMETHING still shorted i the ckt, likely a cap somewhere.

I won't be able to work on this radio again for two weeks, the radio club will all be at the BirmingHAMfest on March 7, and so will I. So I should take all the tubes out and try it on the variac? I kind of suspected it was a capacitor, those darn things love to go short.

I got this ARRL The Radio Amateur's Handbook today while working on my Zenith. It goes into extreme detail on electrical theory of all types. There's some pretty brutal math in there.

In the absence of my Zenith, my 1941 Philco is doing an A1 job. It sounds amazing and hasn't skipped a beat.

The inside. It gets a little warm back there after a while.