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Zenith 7-S-258 back alive
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Author:  Galaxie68 [ Jun Mon 14, 2021 5:58 am ]
Post subject:  Zenith 7-S-258 back alive

Before the Majestic 130-A I'm working on now, finally got to a bedraggled Zenith 7-S-258. I bought this years ago and never tackled it beyond locating a correct 10in speaker for it. 2 weeks back I cleaned it out and dug in. Turns out it had been serviced in the 50's or 60's. Original electrolytic caps already bypassed with those cardboard tubes.

Replaced those. checked tubes, replaced dial belt and warmed up. Terrible oscillation. Oh boy. I mean terrible. Restart, wrote down and numbered all the little film capacitors, All Zenith originals. three 05's, four .02's. one .1 and one .001. I also goofed using an 8uf in circuit. Replaced all those. Warmed up. There's still some odd static though all oscillation is now stopped. Tuning remarkably direct and easy. Ear tuned (barely) the cans and antenna trimmers. Not too far. Just enough to verify in range and bring reception a tad sharper. I have no sig generator. I'm pleased. A beautiful set. Even get a couple shortwave stations. Without an antenna.

The original 6T5 lights brightly yet darker center doesn't react a lot to tuned stations? Is it's dark center suppose to retract smaller as strength of signal increases? Or, will it react better with an antenna?
I'll post photos as soon as I figure out how to transfer to computer.

Ah-dial belt. I used an ACE Hardware 2 1/4 diameter one. $1.49 vs $7.70 for a tan one online. Popped right on.

Author:  Galaxie68 [ Jun Mon 14, 2021 7:14 pm ]
Post subject:  Re: Zenith 7-S-258 back alive

An update including photos. The short vid is an in progress one. The long is after finishing

9693C327-1B96-4651-A161-DEB6BFD4F015.jpeg [ 1.9 MiB | Viewed 483 times ]
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[ Play Quicktime file ] trim.49F67913-23B3-49BC-ADBC-B40152406321.MOV [ 2.8 MiB | Viewed 483 times ]

Author:  Galaxie68 [ Jun Mon 14, 2021 7:22 pm ]
Post subject:  Re: Zenith 7-S-258 back alive

Hmm trouble with vid

Author:  Galaxie68 [ Jun Mon 14, 2021 7:34 pm ]
Post subject:  Re: Zenith 7-S-258 back alive


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Author:  Paul Dietenberger [ Jun Mon 14, 2021 8:19 pm ]
Post subject:  Re: Zenith 7-S-258 back alive

The 6T5, like all eye tubes, reacts to the amount of bias voltage placed on the grid of the IF tube. If you don't have an antenna, you aren't getting enough signal strength to generate much bias voltage, so the eye won't do much. Get 15 feet of flexible wire and tie it to the antenna screw, and see if everything doesn't perform better for you.

The new finish is certainly better looking. Are you satisfied with your grille cloth installation? I get the sense from looking at it that it wasn't completely ironed out.

Author:  Galaxie68 [ Jun Mon 14, 2021 9:50 pm ]
Post subject:  Re: Zenith 7-S-258 back alive

Ah so no worries for now on 6T5 thanks. Yes need some proper antenna wire. I've a couple spare 6E5's so nice to keep original. That grill cloth is two smaller pieces overlapping. Just didn't want to iron set until a chance to find more original. For now it was this or the big piece of yellow wavy. Which, TBH looks so wrong.

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