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output transformer wires

12/2/1997 11:17 PM
paul kreimer
output transformer wires
I have a drake output trans. from a marshall blues breaker reissue. The schematic doesn't list colors for the output wires, just for the ins and center tap. How can I find the ground, 4, 8, 16 ohm wires? Should the schematic be in the same order as the actual trans. Can I look at the colors from the ins and line them up with the output wires and the 4, 8, 16, and ground labels on the schematic?  
12/3/1997 1:09 AM

Use an ohmmeter to find the lowest resistance set. That will be the output wires. Pick two, put a low voltage across them at 100Hz or so from a test oscillator, or perhaps 1/2 of a CT 6.3VAC filament winding, and measure the voltages on the others. A little head scratching will yield the results. The only hard thing is deciding which is common; the other ones fall out directly in order of voltage.  
Do this with ALL THE OTHER WIRES OPEN. The primaries will have a couple of hundred volts on them when you do this.
12/3/1997 9:14 AM
Marshall OT wires color code
I can't remember where I picked this up.  
It is not mine and I'm sorry if I step on anyones toes here!  
Marshall amp output transformer color code  
100 WATT  
brown - common  
green - 16 ohm  
yellow - 8 ohm  
black - 4 ohm  
50 WATT  
orange - common  
yellow - 4 ohm  
green - 8 ohm  
grey - 16 ohm  
Maybe this was helpfull!  
12/3/1997 10:18 AM
Thanks Bruce, this makes it easy, thanks also to RG for a way to test an unknown trans.  

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