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 Post subject: Zenith tuning condenser gearing issue
PostPosted: Dec Tue 05, 2017 8:06 am 
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Location: Toledo, Ohio
I am finishing up the Zenith 6S249 restoration. Noticed the tuning condenser was not being engaged at times by tuning knob.

Here is what I found (or did not find) the drive gear run off the belt moves freely on it's shaft in and out and there is nothing retaining it on the shaft or in place. Thus when tuning it will occasionally slide out of position and no longer engage the tuning condenser drive gear. Of course being spring loaded the tuning condenser will quick spin shut. :x

Other similar Zeniths from this era usually have a slip mounted pulley of some sorts that retains this gear in position. I see nothing on this one or provision for anything...strange. Wondering if there is a piece or part possibly missing.

BTW this is chassis 5644 which is also found in the 6S254 and 6S256. If someone has a chassis on hand they could take a look at it would be greatly appreciated.


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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Tue 05, 2017 3:30 pm 
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Location: Near Brandon, Iowa
The two dial pointers should limit axial movement of the sleeve when they are installed.


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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Tue 05, 2017 10:26 pm 
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Location: Toledo, Ohio
They don't though, and did assemble it in cabinet last night to try it still will ride up and out on occasion. Othe zeniths I have of the same era usually have something to retain the gears-shafts in place. Anyone out there have a 249 254 or256 they could peek at and maybe snap a pic or two?

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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Tue 05, 2017 10:40 pm 
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I have a 249 that is not yet back in the cabinet. But the dial is put back together so I can't see if there is supposed to be anything on the front to hold the shaft in place. The pic I took looks the same as your second pic where the gear is engaged. Sorry I can't be more help. My assumption would have been the same as Lorenz's.


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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Tue 05, 2017 10:45 pm 
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Location: Santee Calif. 92071
Sounds like the belt is slipping. See this link for a very good belt. No slip works great. Your model is listed.

http://www.adamsradio.com/


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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Tue 05, 2017 11:51 pm 
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Joined: Jan Mon 25, 2010 7:51 am
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Location: Toledo, Ohio
Formuser...I don't think there could be any kind of retainer under the dial-arms. I see no provisions what-so-ever there for it such as groove for a circlip or markings from a set screw. On this radio even with the dial face, pointers all in place there is more then enough play to allow to travel up the shaft (happens when tuning) and the gears disengage. You can grab that shaft and move it up and down easily and see the gears engage and disengage (even with the dial face-pointers assembled. So in the case of my radio the dial pointers being assembled do not keep that gear in place.

I have several Zeniths of this era type and often you will see something around the gearing on the shaft between the rear of the dial assembly and front of the tuning condenser. Sometimes it is a washer others a spring steel type set screw-clamp.

As far as the belt...that is not the issue what so ever. The belt was replaced and in great-working order this is not a belt slipping issue, the first gear-shaft riding up out of the next gear whilst tuning the radio.

One thing I did consider is perhaps the belt-tensioner underneath the chassis is set up in a certain way that when spinning the tuning knob-shaft it keeps that gear in place. When I got the radio the belt was gone and tensioner flopping loosely. I set the tensioner up the way I found it on my 10S155, 8S154 but those have retainers to hold the gears in place. Perhaps to save costs Zenith eliminated the retaining system and went with some odd crude belt tensioner design. I have noticed that the pulley on the shaft under the chassis and the other pulley for the gear (that is riding out) do not line up perfectly and this is why that gear rides out of the mesh of the other gear. There could be something that was removed and replaced onetime in the wrong position as well.

Formuser, maybe you could snap a couple pics of your chassis up top and the tensioner on the belt underneath to see how yours is set up. Another set of eyes on it might see something that is not right on mine.

Thanks!

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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Wed 06, 2017 2:09 am 
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Location: Near Brandon, Iowa
The brass driving pulley on the tuning knob shaft can be loosened and repositioned nearly anywhere you want it. You might try moving it back toward the center of the radio a bit. That would tend to keep the problematic driven pulley/gear unit biased toward the tuning cap. The top (driven) pulley will tend to align itself with the bottom (driving) pulley, so if the latter is too far forward, it will "walk" the top pulley out of engagement with its gear.


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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Wed 06, 2017 3:04 am 
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bastardbus wrote:
Wondering if there is a piece or part possibly missing.

BTW this is chassis 5644 which is also found in the 6S254 and 6S256. If someone has a chassis on hand they could take a look at it would be greatly appreciated.


Thinking back a bit. On your third picture if you look at the rear edge of the top belt small gear you will see a bit of a burr where there used to be a thin brass washer that was peened onto the back edge of that small gear. Most likely the washer is long gone but get one that will fit and then solder it to the backside of the gear and that will keep the shaft from moving forward and disengaging from the lower drive gear.

Also you need to replace the rubber gommets that hold your tuner in place. Notice the shaft rubbing the bottom edge of the dial pan. Tuner needs to be boosted back up a bit.
John k9uwa

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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Wed 06, 2017 4:31 am 
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Location: Toledo, Ohio
k9....good job! What you described is EXACTLY what my other Zeniths have and exactly what I thought THIS should have had as well. I pondered what you have described and one of the reasons I posted the question here, to see if someone might be able to verify the above.

lorenz, I already tried what you described and NO that pulley does not move axially on the shaft. There is a shoulder machined into the shaft and the pulley can not be adjusted further. There is a circlip in a groove at the other end of the tensioner assembly that holds this all in place. The screw-spring thingy on the pulley is a tensioner that allows you to adjust the tension of that pulley on the shaft as this acts like a clutch so to speak and though it spins the belt it will spin free when you hit the end of the tuning condenser travel.

P.S. thanks on the condenser grommets, yes I know I need to do those too. Need to order or go by some. I forget are these a special piece or can I just use some std grommets?

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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Wed 06, 2017 5:24 am 
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Location: Leo, IN or Zellwood, FL
bastardbus wrote:
k9....good job! What you described is EXACTLY what my other Zeniths have and exactly what I thought THIS should have had as well. I pondered what you have described and one of the reasons I posted the question here, to see if someone might be able to verify the above.
P.S. thanks on the condenser grommets, yes I know I need to do those too. Need to order or go by some. I forget are these a special piece or can I just use some std grommets?


Happy to help. And on the grommets you might save a bit by coming up with stuff yourself but for the time and effort better to just look to the right of these pages and click up RenovatedRadios.com and get the right parts for this radio. I am sure Ed has them.
John k9uwa

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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Wed 06, 2017 9:06 am 
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Location: Toledo, Ohio
So had some time this eve to tear it down some more and indeed you can see where the retaining washer was, remnants of it just barely left on the edge but you can tell something was there at one time and forcibly removed or worn away.
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I dug through my parts bins and came up with a perfect brass washer, about the exact size I recall on my 8S154 and 10S155 had.
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There was just enough of the shoulder on the drive gear to fit through the center of the washer. I did have to open up the center hole of the washer so part of the drive gear could come through to be soldered. The washer fit perfectly and I soldered it in place. Then sanded it down and opened up the center hole to size with some small files. Here is a couple pics of the washer soldered in place.
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Here is the gear back on the shaft and in place. One has to remove gear #2 of the 3 gears to fit #1 in place with the washer now back in place. Upon removal of gear #2 I noticed a washer underneath that looked incorrect. It was far too large for the shaft and hanging on it sloppily. It did not look like a factory piece. I took another one of the brass washers I had and it fit BEAUTIFULLY on the shaft and flush against the #2 gear. It also re positioned the #2 gear so it drives off the #1 better. Possibly the cause for the destruction of the #1 gear retaining washer??
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So I am thinking at sometime, someone was in here fooling with the gearing on the condenser. I am not quite sure what the initial problem was but it is not possible to remove the #1 gear without removing the #2 first unless you destroy that retaining washer which is possible. Or that odd misplaced washer behind #2 gear might have cause failure of the retaining washer. But I did not see any remnants what so ever of a ground up retaining washer.

After the entire gearing was re assembled I noticed some binding at the high end of the dial. This problem was there prior to my repairs. I couldn't figure it out so took each gear off one by one and found the binding was due to the #3 gear, the one with the return spring, was adjusted to tightly. Loosening the adjustment by just a millimeter or so stopped the spring binding at full open. It works absolutely beautifully now, smooth as silk through the full range of the tuning condenser.

Thanks for the input to everyone. Maybe this will help someone else down the road with the same issue.
T

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 Post subject: Re: Zenith tuning condenser gearing issue
PostPosted: Dec Wed 06, 2017 1:20 pm 
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bastardbus wrote:
retaining washer. But I did not see any remnants what so ever of a ground up retaining washer.

After the entire gearing was re assembled I noticed some binding at the high end of the dial. This problem was there prior to my repairs. I couldn't figure it out so took each gear off one by one and found the binding was due to the #3 gear, the one with the return spring, was adjusted to tightly. Loosening the adjustment by just a millimeter or so stopped the spring binding at full open. It works absolutely beautifully now, smooth as silk through the full range of the tuning condenser.

Thanks for the input to everyone. Maybe this will help someone else down the road with the same issue.
T


Excellent on the repairs.

The brass washer was probably ripped off by someone pulling too hard to remove the dial pointer. As to the Zenith applied load on the return spring they are all way too tightly wound. It is only there to provide a bit of load to reduce he backlash in the gear train. I normally reduce the spring load so that the tuner with no gears attached will just barely return to closed by the spring.

Glad you have it nicely repaired.
John k9uwa

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