Zenith 8s359 - Printable Version
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Zenith 8s359 - klondike98 - 02-03-2018
My latest project is a Zenith 8s359 that belongs to a fellow in town. I volunteered to help him get it playing. Hopefully it will all come together! He had previously done the cabinet so I’ll just be working on the chassis.
[Image: https://www.dropbox.com/s/c09hrv7erprbpx2/zenith8s359_01.jpg?raw=1]
[Image: https://www.dropbox.com/s/ejuzwkwj9rg6x7g/zenith8s359_02.jpg?raw=1]
[Image: https://www.dropbox.com/s/52t4onsw7zawgx9/zenith8s359_03.jpg?raw=1]
He said it had been working when he got it from his Aunt but no longer is. All but one of the tubes test OK, though I haven’t tested the 6U5. There are a few threads about this set on ARF and they talk about the rectifier 6X5 being prone to problems and taking out the transformer if it shorts. The dial string and dial belt are both broken and will need repair. I also read a thread on the Phorum about repairing the tone or station switches and it sounds like a difficult job. Parts are ordered, clean up has begun. Should be fun!
SCHEMATIC LINK
RE: Zenith 8s359 - Electrothaumaturgist - 02-03-2018
That should be a fun little project. I like working on Zeniths, but they do have a reputation for bad transformers, weak rectifiers, etc... Some of the sockets need to be dismantled to change out the meg-ohm resistors, (I think in the eye tube) and the 8s-463 I repaired a few years ago needed most all of its wires replaced, as the rubber insulation had disintegrated. Got new dial string from Mark Oppat If I remember correctly. It was a good sized chassis, with plenty of room to work. Seems the original eye tube was pretty expensive, so I got a whole new socket assembly (old one was fried, I think) for a cheaper retrofit tube-again from Mark Oppat, perhaps. Worked great! That was a very nice performing radio with superb sound. It came equipped with a television jack, which I was able to attach a 1946 Pilot 601 fm converter that I restored just for that. It LOVED to play FM! Good luck with that one!!!
P>S> Don't be afraid of those switches. Just handle them very carefully...
RE: Zenith 8s359 - murf - 02-03-2018
Have done a few of these zeniths.
All prone to bad wiring on the eye tube as well as the tone control.
Just replace one at a time and its not a big deal.
Tone control has to be carefully pried apart to replace the pushbuttons.
After you do it, it will never have to be done again in your lifetime.
Great radios, have many of the mid to late 30's as well as a couple early 40's consoles and chairsides.
Have fun with it, I wish I had a couple more to work on.
I have sold quite a few of these and they always go fast.
Everyone loves the beautiful cabinets and the black dials.
murf
RE: Zenith 8s359 - morzh - 02-03-2018
Bob
If it comes to that 1M resistor inside the eye tube socket, look up my 9-S-262 thread from, I think, 2012. There I described a fix that doesn't require disassembling the socket.
Mike
RE: Zenith 8s359 - klondike98 - 02-03-2018
OK, thanks Mike!
Thanks guys.
More pics soon.
RE: Zenith 8s359 - Arran - 02-04-2018
No these didn't use the expensive eye tube, just a plain old 6U5/6G5, it was the shutter dial sets that used the expensive and rare eye tube called a 6T5. In terms of whether the 6X5 might be a problem it really depends on the current and the voltage, if the current load is under 70 ma and the output voltage stays under 250 volts there shouldn't be a problem. I've never heard of a 6AC5 power output tube, but apparently it's very similar to a 6K6 in heater current, 400 ma, except it's a triode, plate current is 32 ma, grid 5 ma, the rest of the tubes will be much less then that, hopefully they won't add up to more then 35 ma or so. The audio amp is very interesting, it has a first audio amp tube that feeds into a 6P5 which acts as a driver tube for the 6AC5 power output, in a cathode follower setup I believe. The resistors in this thing may need to be checked, they are all 1/4 Watt types which I have found like to drift in value in other radios.
http://www.nostalgiaair.org/pagesbymodel/445/M0025445.pdf
Regards
Arran
RE: Zenith 8s359 - klondike98 - 02-04-2018
Thanks for the info Arran! I was reading about the shuttledials and had heard of them but never really knew what they were about until I saw a Youtube of one in action.
Interesting that you mentioned the resistors. There are a mix of dogbones and newer carbon resistors. I will check them but there is also an 82ohm wirewound resistor that connects the CT of the power transformer to chassis ground. I believe originally it was the piece circled in yellow but at some point in the past was replaced. I do measure 82 ohms between the CT and chassis so there is a resistor in the circuit but I haven't located it yet. I wanted to be sure its not just a 1/4 watt one. Its gotta be there.
[Image: https://www.dropbox.com/s/yyk74ejiavhlqpy/zenith8s359_04.jpg?raw=1]
[Image: https://www.dropbox.com/s/n4vxckrofx6p7e5/zenith8s359_05.jpg?raw=1]
Yes, just a 6U5 tube. Unfortunately the wiring into the tube socket is the old rubber stuff so It will need resleeving or replacing. Looks like most (but not all) of the rest of the wire is cloth covered.
RE: Zenith 8s359 - Electrothaumaturgist - 02-04-2018
Love that flywheel. You can give that dial knob a good twist and send the indicator to one stop, then back to the other. Nice.
RE: Zenith 8s359 - klondike98 - 02-05-2018
The dial pointer has a definite bow to it! Has anyone straightened one of these before? It doesn't actually look too bad when viewing it straight on so I don't want to make things worse.
[Image: https://www.dropbox.com/s/2b6ttthprr9ngs7/zenith8s359_06.jpg?raw=1]
RE: Zenith 8s359 - Arran - 02-05-2018
The 83 Ohm resistor is numbered as R13, it's between the transformer center tap and chassis ground, it can't be a 1/4 Watt resistor as it is supposed to be a wire wound one, unfortunately it does not give the Wattage. I think that the 1/4 Watt must refer to the 1 meg Ohm one between the target and plate in the eye tube socket.
Regards
Arran
RE: Zenith 8s359 - Phlogiston - 02-05-2018
(02-05-2018, 12:51 AM)klondike98 Wrote: The dial pointer has a definite bow to it! Has anyone straightened one of these before? It doesn't actually look too bad when viewing it straight on so I don't want to make things worse.
[Image: https://www.dropbox.com/s/2b6ttthprr9ngs7/zenith8s359_06.jpg?raw=1]
You can do both - that is straighten the pointer AND make it worse. Careful application of heat is the only difference. Use a very flat surface (Iuse a metal plate) and a heat gun on low moving continuously.
The only other problem is that it may have shrunk - whaic isn't so bad. I think there are at least 2 vendors selling replacements - Though I did not go and look - Renovated Radios and Great Northern.
RE: Zenith 8s359 - klondike98 - 02-12-2018
A bit of progress over the last few days. Nothing exciting about the recapping. The set had seen a number of repairs over the years so I went ahead and continued repairing rather than restoring. Did not stuff paper caps and I believe electrolytics were originally under the chassis as well. Here we are partly through recap.
[Image: https://www.dropbox.com/s/20nku046to5dv4s/zenith8s359_10.jpg?raw=1]
I had not rewired a 6U5 socket before. My 1 Meg resistor between pins 4 & 2 was also open as in Mike's thread mentioned earlier but I decided to see if I could open up the socket housing and rewire it internally. Two of the wires were rubber insulated and also needed replacing. After noting wire positions I took the entire assembly out of the radio and using a large nail set through the back side where the wires came out I was able to tap the front plastic face plate out without damage. The metal sockets are individually mounted in small wells in the plastic and freely come out once the face plate is off.
[Image: https://www.dropbox.com/s/oza80r82aour903/zenith8s359_07.jpg?raw=1]
It took a bit of manipulation, measuring and swearing to get the 1 Meg resistor positioned correctly so the 2 and 4 sockets would fit correctly. Rewiring was relatively easy and then tapping the face plate back into place.
[Image: https://www.dropbox.com/s/ff2f4y0bzw6d5f1/zenith8s359_08.jpg?raw=1]
[Image: https://www.dropbox.com/s/2c2qewfkh8ide6d/zenith8s359_09.jpg?raw=1]
I'll put it back in the chassis later today or tomorrow.
RE: Zenith 8s359 - OldRestorer - 02-12-2018
That ripped piece of cardboard used to be a paper ecap box I think.
I have had a few of them in my radios. One rivet and a silver box.
I'm not 100% but I figured I would mention it.
Lookin good Bob...
RE: Zenith 8s359 - Radioroslyn - 02-12-2018
Looks like your 82 ohm resistor should be in the 3-5w range. Actual dissipation is a little over a watt.
RE: Zenith 8s359 - klondike98 - 02-12-2018
Ok, thanks Kirk. I just pulled that out and tossed it.
Terry, thanks. I did find where they put the 82 ohm resistor, its one of those old molded resistors with dots on it. I will probably replace it.