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Adam Munich

Tue Feb 22 2011, 12:03AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

I've been putting together a heathkit Ol-1 scope and the transformer that came with it is different than the one in the instructions. It's a Stancor 54-119 and I can't find any info on it. May I ask, what color wires are usually the mains input? If I can feed it 120V I can measure the output voltages and hook the thing up.

James

Tue Feb 22 2011, 12:24AM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

You found an unbuilt vintage kit? Those usually fetch big bucks. You may be able to get a datasheet from Stancore, I found one for some 70s vintage low voltage transformers. Failing that, measure the impedance of the windings with a meter and you can probably figure out the rest. There will probably be one HV winding with a relatively high impedance, one mains winding with a somewhat lower impedance, and at least one 6.3V filament winding that will measure a practically short circuit. If you find the filament winding you can feed around 6VAC from another transformer into that and measure the voltage across the other windings. The nice thing about transformers is they work both ways. Feed the rated voltage to any one winding and the rest will produce approximately their rated voltage.

Weston

Tue Feb 22 2011, 02:24AM

Registered Member #1316 Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365

Older power transformers for tube era equipment often have a color coding scheme. The scheme is relatively universal. I cant think of what to google on what to find it, but the code is out there. Most of the old radio books also have details on the color code scheme. All I remember about it is that the all the center taps are the striped wires.

radiotech

Tue Feb 22 2011, 03:07AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Well the wire count tally agrees. Do you have the Heathkit
origninal schematic? if not. I have one here. Voltage testing is
not recommended, if there is history of DMM smoking in your
family. Best use ohmmeter.

The filaments 3 of them, -low resistance. middle resistance,
primary. Highest resistance , there will be 3 of them, -and- all
will be associated with a winding with 5 terminals. of which 2 will
have low resistance.

And I know the OL-1, have one somewhere abouts, and have built a couple of them.

Dont drop the CRT.

Adam Munich

Tue Feb 22 2011, 07:20AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Hmm... The maximum voltage it puts out is supposedly 800V, so I think I'm safe.

As for the wires it has:
A pair of white wires.
A pair of black ones.
A pair of green ones.
A pair of red ones.
Another pair of white ones.
A yello/red one.

And the crt seems really fragile, I'll take care not to drop it.

radiotech

Wed Feb 23 2011, 04:08AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The voltages for the 5 wire coil for high voltage and filament for the 1V2 are as follows.:

All in series (additive) 0.625 voltsYellow
510 Yellow
360 Red
0 Red-Y
360 Red
--------
Total RMS 1240 end to end- transformer alone
In the scope WRT ground 875.625 high side
360. low side.\
If you run the transformer alone, unloaded by the tubes and
free of a metalic connection to the 0 terminal, you risk smoking
it due to the 60+ year age, and old insulation.
The colors on the schematic are green- green 6.3 volt for all tubes (2.0 amp) except eht rectifier and crt.
The CRT filament is connected to brown brown. (0.6 amp)
Primary black- black .
I do not know how the Stancor is coded.
Trying to trace windings with DMM will lead to errors due to
winding-winding-case capacitance.

Most 65 year old scopes that smoke are because the transformer high voltage winding burned out due to age.I have at least 3 including the 0L1 which I retro'd about 40 years ago because it
burned our and in 1970 NO SPARE PARTS WERE AVAILABLE.

Is this a kit, or a built one you are repairing with the Stancor transformer.?

Adam Munich

Wed Feb 23 2011, 04:42AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

It's a kit that was disassembled, and I'm reassembling it. Apparently the guy that built it before me used the stancor tranny.

Side 1:
Black - Black = 15 ohms
- regular insulation, primary

White to white = 1.7 ohms
- Thick insulation, probably the crt heater.

Side 2:
Green - Green = 1.7 ohms
- regular insulation, tube heaters

red/yel to whites = .5k
360V windings.

red/yel to reds = a bazillion ohms
red - red - 34 ohms
-Thick insulation, isolated from everything else. Idunno

Maybe I could hook it up to a variac and feed it 60V to prevent magic smoke escape, then double my measurements...

dude_500

Fri Feb 25 2011, 03:21PM

Registered Member #2288 Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179

I always just put a winding on a variac and see what happens... with a lot of mapping and logic you can figure out even relatively complex transformers with dozens of windings. Also put a current meter on the variac, if it starts to go up as you turn the winding up, you know you've hit one that is rated for less than 110 and is therefore a secondary. Turn it up slow at first, if you hit a 6.3V winding on your variac obviously you won't want to shoot that voltage up fast into it, and you'll know pretty quickly that it's not the primary.

This can be particularly easy if you already know at least roughly the designed secondary configurations and voltages.

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