Junk Transformers

[W9ZSL]

I got a few junkers over the weekend and have one that looks to be a TV type for a solid-state rectifier (no CT).  I put the ohm meter on it and the only leads that I determined to be the primary reads only .3 ohms.  The secondary is over 8 ohms but there is a mish-mash of other leads reading 3.5 which could be 6.3 volts.  I'm wondering if .3 ohms for a primary makes any sense. 

[KA2DZT]

6.3v windings would read very low, less than an ohm.  The .3 ohm winding could be the primary.  Any numbers on the xfmr??

Fred

[N8ETQ]

          You could just apply 6.3 VAC to the leads you suspect are and measure the others looking for 120....

GL

/Dan

[W9ZSL]

I'll eventually get it on the bench and hook a variac up to it.  There are 12 leads total.  It has two sets of numbers 95-2922 and 549-7114 just below the first.  I re-measured the resistance of everything.  There is a black pair, probably the primary at .35 ohms.  The secondary appears to be a red/yellow-red pair at 7.5 ohms, no CT.  There is a heavy slate-slate/red pair .8 ohms, a medium slate pair at .3 ohms.  The heavy green pair is indeed .1 ohms with a yellow/green CT.  There is a black/yellow which measures 2.9 ohms between it, the greens and the green/yellow.    Core is 2".  It's hard to say where it came from. 

[W2PFY]

I think the black leads on more modern transformer are the primary on most US mfg transformers. Another way to safely hook it up would be to use a 100 watt bulb if you can find one, in series with the primary. If the bulb goes full brilliance, it could mean a wrong winding or a shorted transformer.

[WD8BIL]

The heavy green pair is the filament winding.

[W9ZSL]

I know the heavy green is filament.  I'll probably put 6.3 on it and check voltage on the black pair.  Once I locate the primary I usually put 12 volts on it then measure the voltages on the secondary then multiply by 10. Of course, I doubt that the primary will be 120.  Iron is too old.  I don't think there is a 5 volt winding for a rectifier since the apparent HV winding has no center tap.  I'm thinking this had a solid-state rectifier.  I'll slap a FW bridge on it for a smoke test.

[WD8BIL]

Yes, 12V filament is usually brown. I have seen them yellow but most often that is reserved for 5V. Sounds like you have a handle on it.

[KD6VXI]

Used to be,  typical xformer color code was listed in reference section of he handbook.

Not sure about now,  though....

--Shane
KD6VXI

[KA2DZT]

I'll eventually get it on the bench and hook a variac up to it.  There are 12 leads total.  It has two sets of numbers 95-2922 and 549-7114 just below the first.  I re-measured the resistance of everything.  There is a black pair, probably the primary at .35 ohms.  The secondary appears to be a red/yellow-red pair at 7.5 ohms, no CT.  There is a heavy slate-slate/red pair .8 ohms, a medium slate pair at .3 ohms.  The heavy green pair is indeed .1 ohms with a yellow/green CT.  There is a black/yellow which measures 2.9 ohms between it, the greens and the green/yellow.    Core is 2".  It's hard to say where it came from.  

The 95-2922 is a Zenith xfmr, I'll try to cross reference it but most likely it's a useless xfmr not good for any ham use.

This xfmr is listed in my book but there is no Stancor or Thordarson replacement which would give some idea what the xfmr is.

[W9ZSL]

If it's a Zenith, it almost certainly came from a TV which would make sense because the guy I got it from was a tech for a Zenith dealer.  The color-coding is a bit strange.  Got the green, black and red/red-yellow.  Don't know about the others.  Maybe I'll build a simple CW rig.  I have a Hammarlund rcvr cabinet that needs filling.

[KA2DZT]

If it's a Zenith, it almost certainly came from a TV which would make sense because the guy I got it from was a tech for a Zenith dealer.  The color-coding is a bit strange.  Got the green, black and red/red-yellow.  Don't know about the others.  Maybe I'll build a simple CW rig.  I have a Hammarlund rcvr cabinet that needs filling.

The 95- number is a dead give away, all Zenith xfmr part numbers of that early era started with 95-.  Most all TV xfmrs used strange colors for the lead wires.  Not unusual for there to be no two leads having the same color.  The 95-2922 is from a TV built somewhere between 1971 and 1975.  These TVs used both tubes and solid state stages so there will be one or more 6.3 volt windings.  The damper tube almost always used a separate filament winding because of the very high negative voltage on the cathode, the filament also was biased with this high voltage.  The remaining 6.3 volt tubes most probably ran from a second 6.3v winding.  So, the 6.3v damper winding will be good for about 1-1.5 amps, the other 6.3v winding good for maybe 4-5 amps.

The primary most likely uses at least one black wire and another black/tracer wire.  Look for the primary first, it will be very low resistance, less than an ohm.  The 6.3v windings will also be very low resistance, less than 1/2 ohm.

There will be at least one high voltage winding, most likely a voltage doubler circuit, no CT, probably good for 400-700 ma.  There could also be a 115v winding to feed the degaussing coil.  The rest of the windings would be low voltage windings for the solid state circuits.

Fred

[WZ1M]

There is no standard color code for transformers. Just a table that says there is. I see primary's from black to red to white. The most consistent coding I have seen is 6.3 volt green, 5 volt yellow. That is all and even that varies. Output transformers are the worst in color coding. Ask me why I know this, I rewind transformers and have just about seen it all.
Regards,
TRS
Gary

[W9ZSL]

That makes sense.

[Opcom]

Those with a non-CT winding, maybe 400VAC, are really great for a bridge and can usually take big overloads for short times without dropping the voltage much. The supply was often C input and sometimes included a 2-4H choke and a large C after. I used to rutinely draw 500+mA from one of those out of an RCA set. They are prominently featured in many linear amp/power supply articles and used with voltage doublers in them. Enormous "IVS" ratings for SSB, but good service for AM too.