Have you tried to contact V.A.C. to see if they have any spares left?
I bought power transformer with dual primary for my early 8B model (I'm in Europe) and also two TC5 chokes from them back in the day.
VAC / Valve Amplification Company - Manufactures Marantz Classic Tube HiFi Components
VAC - Parts for the Audio Hobbyist - Transformers, Capacitors, Etc.
I bought power transformer with dual primary for my early 8B model (I'm in Europe) and also two TC5 chokes from them back in the day.
VAC / Valve Amplification Company - Manufactures Marantz Classic Tube HiFi Components
VAC - Parts for the Audio Hobbyist - Transformers, Capacitors, Etc.
Well, I made what I thought was the right call and sent the power transformer and choke to be rewound professionally.
After receiving the units back, I run it through a few tests...
When I bring the voltage up on the bench through my variac, I notice two things. 1. The center tap voltage on the filamnet windings is not centered. It is off by about 1/2 volt (2.6vac + 3.6vac). Second, when I bring the primary voltage up, the transformer makes a STRONG mechanical hum when the line voltage is increased past 85~90% (with all the secondaries open). I shut it back down quickly. This doesnt seem right, and I dont want to put it into the amp with it acting like this. Should I be testing the transformer under load? What is the proper method to do this on the bench?
After receiving the units back, I run it through a few tests...
When I bring the voltage up on the bench through my variac, I notice two things. 1. The center tap voltage on the filamnet windings is not centered. It is off by about 1/2 volt (2.6vac + 3.6vac). Second, when I bring the primary voltage up, the transformer makes a STRONG mechanical hum when the line voltage is increased past 85~90% (with all the secondaries open). I shut it back down quickly. This doesnt seem right, and I dont want to put it into the amp with it acting like this. Should I be testing the transformer under load? What is the proper method to do this on the bench?
After further investigation, I found some more clues on the transformer hum. When I pull the top off the housing, I see it is only potted about 1/2 way up the transformer. Is this typical? If I push on the lamination where the red arrow is at, the hum changes - the laminations are obviously resonating. I am thinking if the potting covered the entire transformer, the hum would be significantly reduced, if not gone. Does anyone have any first hand experience with potting transformers ? I plan to call the folks who rewound this for me later this week (traveling currently).
That does not look right to me. On the amp I rebuilt, the PT had been hot and some of potting tar had softened and leaked. It was full when I opened it.
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