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 Post subject: Re: Zenith 95-1148 IF Transformer
PostPosted: Mar Mon 25, 2019 12:15 am 
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Location: Petaluma, California
After a long series of failures, I finally have a BC signal coming in nice and clear, but not at the volume I'd expect from this radio. I am trying to replace the mica/silver disc on the 95-1149 and 1148 and figure out how to wire the caps to mimic the discs. The 1148 was straight forward using two 100 pF mica caps across the two sets of terminals wired to the coils.

The 1149 isn't so simple, as it is now, it takes 3 100 pF mica caps, one bridging terminals 8 and 1 (upper coil) and one on 6 and 7 (lower coil) if you count the slots from the alignment arrow on the phenolic base in a clockwise fashion. The third 100 pF mica cap goes from terminal 3 which is B- to 8. Terminal 8 ends up with two caps connected to it as shown in the triple cap in the schematic above.

One odd effect is a kind of harp like sound out of the speaker if you tap any wires in the area between the two IF cans or a ping if you tap the chassis in this area. Also, then turning the volume off, you get a slight ping as well.

I'm going to put this away for now, can't get it 100% but I stuffed a note in the chassis so when I do get back to it, I'll know where I left off.

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 Post subject: Re: Zenith 95-1148 IF Transformer
PostPosted: Mar Mon 25, 2019 12:42 am 
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Joined: Jul Tue 15, 2008 6:13 pm
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Location: Gretna, Nebraska
The two caps on secondary of this transformer are a little confusing. The two are caps wired in series with the center connection tied to pin 6. The other two connections are tied to pin 3 and pin 7.
Is this how you wired up your replacements for the disk?

Not sure what the actual values are, but assume you have those figured out.

Attachment:
95-1149.jpg
95-1149.jpg [ 14.79 KiB | Viewed 203 times ]

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 Post subject: Re: Zenith 95-1148 IF Transformer
PostPosted: Mar Mon 25, 2019 2:42 am 
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The schematic you reference is from the Radiomuseum's two sheet set, which I have but I never realized what those numbers referenced and I am not sure how they count pins on these cans. There is the other "famous" picture zenithifxfmrs.gif by Daniel Schoo which does not have an 1148/49 xformers, but Mr. Schoo does count clockwise from the arrow mark 1 to 8 on this form factor. Do you think Schoo's and that RM schematic count the same way? I tried to use the "Schoo" method :shock:

Attachment:
Schoo diagram.PNG
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 Post subject: Re: Zenith 95-1148 IF Transformer
PostPosted: Mar Mon 25, 2019 2:59 am 
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I have used that diagram in the past and it appeared to be correct when compared to the actual transformer and how the radio was wired to the primary and secondary of the transformer.

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