Metropoulos Forum

How to determine secondary wires colors for sure?

I think my transformer has a wrong wire color for the secondary. Output Transformer: 1202-132 Marstran.

I ´ve found that the color wires for the secondary OT is wrong. The website said:
Orange - common
Gray - 16ohms
Green - 8ohms
Yellow - 4ohms

But I think this is wrong. I´ve put 40volts AC at primary and found:
(commom)Orange + gray : ~3.8volts = 1.7K primary OK
(commom)Orange + green: ~1.9volts = 3.5K primary
(commom)Orange + Yellow: ~0.9 volts (very low value) ~40volts divide by 0.9 = 44.4 = square(44.4) =1.971,36 * 4ohms = 7.8 kohms ??? too high for primary impedance. What do you think?

I think the correct wire diagram is (~40 voltsAC at primary gives a reading):
Gray = Common
Green = 4omhs ~2 volts ~ 1.65kohms
Yellow = 8 omhs ~2.9volts ~ 1.6kohms
Orange = 16omhs ~3.9 volts ~ 1.6Komhs

I've take a read on other OT classic tone C1998, and the voltage range is the same. Same thing, put 40 volts, and the secondary is the same voltage range. The primary impedance is 1.7K for 100W 4 EL34 OT

First I´ve put the wrong(website wire diagram) Marstran OT wires and the sound was very high pith noisy if the orange(common by marstran) is grounded. The only wire that accept ground is the gray wire. All others come the high pith noisy sound.


thanks

that seems right except 1.6k is a little low.

Roe,

thanks for the confirmation. I think the primary AC voltage was a little close to ~41. I´ll try with higher voltage on primary. I was worry about that ratio calculation.

thanks

Let's say I have a transformer with 3 coils. When primary coil is connected to 230V, two secondaries output 12V. Wires are color coded, but I don't know what colors stand for and there is no information about that on manufacturer's website. You should also see best inverter for your need.