Zenith Power Transformer Connections

[EdKozk2]

I have an old Zenith Power transformer I pulled from a set long ago.
I tested all the windings and there fine. I'm not sure which pair of wires
are the 120VAC primary windings. The transformer has 14 wires coming out.
The Zenith number is 95-3172. From what I could find from a google
search is it was used in a 23GC45 and 25GC45 television. The Sam's folder is
supposed to be 1558-2, a mid seventies set. Of the 14 wires, 4 pairs are isolated. The other 6, are taps of a single winding. One of the pairs have plastic insulation, the other 3 pairs are cloth covered.
Would any happen to know which pair of leads are for the Primary or happen to have a schematic of the power supply ?
Thanks,
Ed

[Electronic M]

I don't know if I have any literature or not, but a safe-ish way of finding out what is what that I have used in the past is to take a 6.3V transformer (or tap into the heater windings of another set) and try connecting them to the ends of different windings of the mystery transformer. I then look at the voltages the other windings produce. Eventually you will find an input winding that makes another output winding produce around 120VAC and all other windings produce sane readings. By using 6.3V as the input you reduce the chance of damaging the lower voltage windings by applying too much voltage/current to them.

Just be careful not to let winding shorts happen from the loose leads touching, and be careful not to touch more than one lead at a time.

[EdKozk2]

Hi Tom,
I already tested the transformer. I use a 0-130 vac power supply to slowly bring up the voltage. Trouble with this tansformer is, it has two pairs of almost identical windings. When I applied 120vac to either of the pairs I get the same output readings on the other windings. Some of these Zenith transformers had a 120vac winding just for the
degaussing coil. The set set may have been 100% solid state by mid 70's.
Ed

[zeno]

I dont remember the name but its a special transformer
that uses an oil fill cap across one of the windings for
regulation. All Zenith colors used it from E-line through K
line. IIRC without the cap the transformer will pulsate.
I can dig tomorrow for the manual & give you the color codes.

73 Zeno

[rca2000]

Several names for it. Constant voltage transformer. Ferro-resonant transformer. Voltage regulating transformer. ALL mean the same thing. A transformer which uses forced core saturation to hold the output voltage steady..regardless of load or line changes(within reason of course). That oil cap is across the main secondary winding and tunes the winding in some way--without it--it will NOT regulate right and ALL voltages out of it will be quite low.

I would say the primary winding will be around 2-4 ohms--likely no lower or higher. The main secondary will be somewhat higher--and any LV secondaries will be a LOT lower likely.

[EdKozk2]

Originally Posted by zeno

I dont remember the name but its a special transformer
that uses an oil fill cap across one of the windings for
regulation. All Zenith colors used it from E-line through K
line. IIRC without the cap the transformer will pulsate.
I can dig tomorrow for the manual & give you the color codes.

73 Zeno

Thanks Zeno,
I thought someone would know about this transformer. The oil filled cap
you mentioned, are they still around ?
Ed

[NoPegs]

Originally Posted by EdKozk2

I have an old Zenith Power transformer I pulled from a set long ago.
I tested all the windings and there fine. I'm not sure which pair of wires
are the 120VAC primary windings. The transformer has 14 wires coming out.
The Zenith number is 95-3172. From what I could find from a google
search is it was used in a 23GC45 and 25GC45 television. The Sam's folder is
supposed to be 1558-2, a mid seventies set. Of the 14 wires, 4 pairs are isolated. The other 6, are taps of a single winding. One of the pairs have plastic insulation, the other 3 pairs are cloth covered.
Would any happen to know which pair of leads are for the Primary or happen to have a schematic of the power supply ?
Thanks,
Ed

Can you take the bells off the ends of the transformer to potentially see where the leads wind up inside? Often you can get a feel for things by how deep in the bobbin they are, if they're insulated particularly heavily, or if you're really lucky you can observe the wire gauge of the actual winding where it connects to the lead wires.

[Findm-Keepm]

Originally Posted by EdKozk2

Thanks Zeno,
I thought someone would know about this transformer. The oil filled cap
you mentioned, are they still around ?
Ed

Yep. The caps are similar to motor start capacitors. Zenith used them with Ferro-resonant transformers - a great way to economically get some regulation of output voltages. It is fairly old technology, but works great when the caps are healthy. I recall replacing maybe two or three of the caps in 20+ years of servicing Zenith Duramodule sets. The caps are 3.75 or 4 microfarads, at 240 volts, IIRC, and were standard size. I was in Lebanon, TN once, and had to fix my uncles Zenith - a trip to a local hardware store was all I needed to buy the cap, as they had an air conditioner motor start (or run, don't remember now) capacitor of the same value. Be careful - AC bites!

Cheers,

[EdKozk2]

Brian, I probably have some of those oil caps lying around.
I went back to check another Sam's Folder I do have,1377-3 for a Zenith
17EC45/19EC45 chassis. It shows the an oil filled cap connected in the
multi - tap winding of the secondary. The cap shown was a 3.5 uf @ 440 vac.
Unfortunately the Zenith 17/19EC45 power transformer 95-3123 is not the same
for the Zenith 23/25GC45 chassis. I guess the secondary output voltage would have a
bearing on the oil cap's AC value.
NoPegs the old Zenith power transformers have that heavy paint/tar? coating on the
bells. I'll wait to see what Zeno comes up with.

[zeno]

OK this is from the G line manual.
It calls for a 95-3172-01 so may be different.

primary grey & grey brown 3.3 ohm
sec #1 black & black green 8.8 ohm for DGS
sec #2 blue & yellow filament 6.3 V 840ma
sec #3 white & black yellow 3.5mfd cap only
red yellow tap to ground
red black 135V
green 35V
green 35V
brown 6V
red 135V

73 Zeno

[EdKozk2]

Thanks for the trouble Zeno, I'll see how
the info matches.
Ed

[Findm-Keepm]

Originally Posted by zeno

OK this is from the G line manual.
It calls for a 95-3172-01 so may be different.

primary grey & grey brown 3.3 ohm
sec #1 black & black green 8.8 ohm for DGS
sec #2 blue & yellow filament 6.3 V 840ma
sec #3 white & black yellow 3.5mfd cap only
red yellow tap to ground
red black 135V
green 35V
green 35V
brown 6V
red 135V

73 Zeno

My Zenith tranny listing shows the -01 to have UL mods, probably the beefier insulation when they changed the UL requirements in 77/78. Zenith microfiche also shows the -01 mod to be the only orderable part - the orig tranny is subbed by the -01. Also, some trannys had the suffix rubber stamped in silver or gray paint after the stamped-in-steel part number.

Cheers,

[EdKozk2]

Thanks you to everyone who helped me identify the leads of the Zenith
95-3172 transformer. Those resistance readings, made all the difference.
I tested the transformer without an oil cap and the HV 135v lead only read
100-103vac. When connected the oil cap the transformer voltages came
right up specs.
Ed

[Electronic M]

So what are you planning to use that transformer in? I can think of a number of interesting uses for one of those.

[EdKozk2]

Originally Posted by Electronic M

So what are you planning to use that transformer in? I can think of a number of interesting uses for one of those.

Well Tom,
I was going to use it for a multi -purpose power supply, which I may still do. I was hoping it had a very high current low voltage winding. For instance; 8 to 30 volts @ 5 to 10 amps.
For now I'm going to use an old Zenith 95-2141 power transformer. Its from a mid sixties B&W set I stripped in the 70's. It has two output windings; 115vac@ .3 amp and 6.3vac @ 8.9 amps. I needed lots of filament current for 5 volt tubes like the old cx201's used in 1920's battery sets. I,m using a 12 amp bridge rectifier for a 1.4v drop from 6.3v to 4.9volts. The 115 volt secondaries current may be overkill, but I have plenty of current for tubes like the 6080 which I use now and then.
Ed