::Hello
:: Can anyone tell me where I might be able to buy a cardohm resister for a Zenith 12 U 159 console radio? Thanks again

Terry F

.

Bill VA

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That's what I did for my GE106 and it works great! I agree with you that rebuilding a portion is not the best way to go (even though it is more of a challenge).

Terry F

Thank all of you for your sugestions.I find another problem with each day.This model has two speakers.Both have open field coils.One section of the cardohm is automatically switched out when the speaker plug is inserted in set.I have a choke from an old crosley which is 1400 ohms that I thought of useing with an old permanent maqnet 12 inch speaker.I guess I can cut the field coil clear in the smaller speaker and substitute another choke or a resister.It begins to get confusing as the only information I have is from the Riders schematic. I have all the caps replaced and the new power trans former installed and a 1400 ohm choke installed for the open field coil of the 12 inch speaker.There is a note on the Riders schematic that states # 2 speaker field is automatically substituted for 4535 ohm section of candohm resister when speaker plug is inserted in set but does not say or show how.O well no great rush.Thank you all again

Sir Daniel

I never did see specific reference supplied as to what specific section(s) of that Muter / Candohm that your BIG Zenith had bad in it.
I’m always just seeing the smaller “Walton “ series of chassis where its typically the 11k sections that fail.

Since you probably have that chassis accessible, you might be doing a great service to others in the future if you were to take resistive readings
of each of its 5 separate sections and post them here.

If one is depending upon Riders of that time frame for info from the “lettering” in of the values on the schematic, that is just not proving adequate
in its clarity.

For an example of its readability:

On the very top section…is it… 4..yes…9?...3?....5…yes

On the next section….… is it …4..yes…4…yes…6?...5?

On the next section……..is it….4?..........4 yes

On the next section……..is it….1.yes….9?

On the bottom section…is it ….9? or 3?.............. 5..yes 0…yes

Sooooo, could you take ohmmeter in hand and see what those resistive values meter out as. Its for sure that you are going to get a better reading
than the service literature composed back at those times is now presenting.

Plus, nowadays , its hard to interpolate the values of resistance via computational means, SINCE, when the circuitry is operating there is
additional resistive shunting being presented by the load lines that are tied into the taps. That factor alone precludes simple ratiometric and
propoprtional computation of those resistors value in a static condition.

On the Muter’s typical manner of tapping in to get ohmic connectivity, one finds a conductive strap encircling almost all of the resistor at the tap
point such that the semi encircling clamp then gets compressed so that contact is made with all of the mass of nichrome wire turns being covered
up underneath the clamped area, with the extension of the clamp metal extended outward to be that terminal of that tap.

Failure mode is typically from cumulative atmospheric / humidity / gaseous exposure such that a combination of developed oxide and dissimilar
metal disassociation factors occur. With time partial ohmic connectivity is breached at some areas on the edge …(more exposed)… portions
under the clamped area. That can cause a shift in resistive value as a turn(s) that was initially shorted out, then enters its series resistance into the path.

The real bad situation, was the development of a erosive point on a turn where a decrease in effective diameter at that minute area, would have
a progressive weakness evolving such that would eventually be the failure point.

Overall, the wire wound aspect was quite acceptable in its performance and long term resistive value stability, much more than could be said for
multiple power carbon composition resistors used in that application.

On the units that I replaced power sections individually, I was long ago impressed by Dales construction of a power resistor with its element
proper being sealed within a finned aluminum housing which could then be heat sinked onto a chassis pan with its mounting lugs.

Therefore, that was the type of unit that I would use in the future.

I performed that construction procedure by a placing of two units, end terminal to end terminal, and taking an ~1/4-3/8 inch length of brass
tuning from the hobby shop, or the K&S metals section of full service hardware stores. I would then use an abrasive #411 or 412 Mini cut-off
wheel mounted in a Dremel tool to cut off half of those end terminals and round their internal terminal slot profile to then accept ½ of the diameter
of that 1/8 dia brass tubing section. I very slightly solder tacked the three together initially and then made use of a single bare strand of copper wire
salvaged from an AC line cord.

That wire was liberally fluxed and tinned and then interwrapped with a few turns being close to the tubing and to both end terminals to get a
mechanical interbinding and then a light solder connection is made. Lastly, fluxing the inside of the short tubing portion and popping of the
terminating wire inside the tubing terminal.
Thassit… .

Visually….. as per:

73's de Edd

::I second the motion. Rebuild the whole string. If one section it out the rest are soon to follow. Bridging a bad section is easy but asking for more trouble. Sometimes the bridged section can "heal" itself as the section warms up, thereby yielding half the intended resistance (parallel resistance) with the original resistance plus the bridged value. Use appropriate wattage resistors for proper heat dissipation. The original candohm strip used asbestos inside. Mouser Electronics has special clips by Ohmite that can help heat-sink the appropriate sized power resistor to the chassis. I did this for a friend's GE 105E and it worked out great. If you want a picture, e-mail me to see a picture of the replacement of the candohm strip. Here's a link of someone else's replacement of a candohm that looks good: http://www.antiqueradios.com/forums/viewtopic.php?t=4926&view=previous&sid=c34e67e9d3358c108a5f9e5e92f92be2
::Good luck with your restoration. Let us know how it comes out in the end.
::Steve
:
:
:Thank all of you for your sugestions.I find another problem with each day.This model has two speakers.Both have open field coils.One section of the cardohm is automatically switched out when the speaker plug is inserted in set.I have a choke from an old crosley which is 1400 ohms that I thought of useing with an old permanent maqnet 12 inch speaker.I guess I can cut the field coil clear in the smaller speaker and substitute another choke or a resister.It begins to get confusing as the only information I have is from the Riders schematic. I have all the caps replaced and the new power trans former installed and a 1400 ohm choke installed for the open field coil of the 12 inch speaker.There is a note on the Riders schematic that states # 2 speaker field is automatically substituted for 4535 ohm section of candohm resister when speaker plug is inserted in set but does not say or show how.O well no great rush.Thank you all again