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 Post subject: Zenith caps
PostPosted: Apr Wed 08, 2020 3:58 pm 
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Joined: Nov Sat 16, 2019 2:14 am
Posts: 42
Location: Oconomowoc, wi 53066
Am working on a zenith model t600 chassis T640 with IF transformer # 95-1149 with SMD dose any one know the values of the caps for the primary and secondary? I tried 100uuf but didn't work
Primary and secondary read 24 ohms.
Forrest.


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 Post subject: Re: Zenith caps
PostPosted: Apr Wed 08, 2020 4:04 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 29054
Location: Annapolis, MD
First, the DC resistance is irrelevant....

I use one of 2 methods:
1. After removing the bad caps and reassemlbing, measure the inductance of the windings and calculate the required C.

2. Set up the IF transformer and a scope (0r anything that will respond to the IF frequency**). Put in you best guess for C (just one one winding for starters) and find the resonant frequency. This will then tell tell you how much to change C to get to the right place.

Both methods use the same basic equation: f at resonance = 0.159 / sqrt(L*C)

**PS: to measure the response, I think you could just put a small "signal diode" in series with the output and measure DC voltage with a VTVM or DMM.

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-Mark
"Voltage is fun to watch, but it's the CURRENT that does the work."


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 Post subject: Re: Zenith caps
PostPosted: Apr Wed 08, 2020 5:01 pm 
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Joined: Jan Mon 18, 2010 2:13 am
Posts: 21466
Location: Dayton Ohio
I'll remove incorrect info. Trying to remember anything I ever did seems to be a waste of time... :(

-Steve

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Consoles and floor models, the bigger, the better!


Last edited by azenithnut on Apr Wed 08, 2020 9:50 pm, edited 1 time in total.

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 Post subject: Re: Zenith caps
PostPosted: Apr Wed 08, 2020 7:24 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 14682
Location: Mountains of Mourne. Ireland.
Values can be seen here...

viewtopic.php?p=3006161#p3006161
viewtopic.php?p=3150868#p3150868

Use the top box only here at arf (google site search).
search.php

Use... Quotation marks to search for a phrase, as seen here...
“one tube radio” site:antiqueradios.com
https://www.google.com/search?q=%E2%80% ... 8&oe=utf-8

------------

As mentioned by Mark...

The Resistance values given in Ohms (on the schematic) for the transformer's primary and secondary coil
are just for the benefit of the bench serviceman and his trusty multimeter.

Regard them as ballpark values - - or, as... good or bad.


Your I.F. Transformer's coils/windings are inductors, and inductance is measured in units
called henrys.

(therefore) in the design and construction of circuits, coils are chosen for their inductance.


An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component
that stores energy in a magnetic field when electric current flows through it. An inductor typically
consists of an insulated wire wound into a coil.

Greg.


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 Post subject: Re: Zenith caps
PostPosted: Apr Wed 08, 2020 7:34 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 14682
Location: Mountains of Mourne. Ireland.
If you require the nine-page Photofact service manual, Set-254 Folder-13 shoot me an e-mail address via PM (private message).

I think you mean chassis 6T40
Greg.


ref: https://www.samswebsite.com/en/photofac ... sid/254_13


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 Post subject: Re: Zenith caps
PostPosted: Apr Wed 08, 2020 9:55 pm 
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Joined: Nov Sat 16, 2019 2:14 am
Posts: 42
Location: Oconomowoc, wi 53066
Problem solved thank all of you for your input.
Forrest.


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