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Originally Posted by Jonathan
Tubejunkie,
My power transformer has a similar number. 940157 274/1SUB5 719
The filament of one of my 5U4's was burned open too. When there is no load on the secondary B+ winding (rectifiers out) it doesn't smoke at all, so I just don't know.
Thanks.
Jonathan
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Jonathan, first I must state that although both of our sets are of similar vintage and design they are very different. They are comparable enough for us to trade notes until we both have our RCA's working well. Luckily the power supply is one of the easier circuits to understand. Again, I was worrying myself trying to get resistance measurements while in denial of the real need for a transformer.
I disconnected everything and still had a smoker. Cut and dry.. Your case Jonathan is much different. You say that you only have a problem when you add the rectifiers. So you know that the transformer is not the problem. You have a dead short somewhere after the 5U4's. Cut and dry. To anyone else I would say you probably have shorted B+ filters due to age. You have already changed out your caps if I read right. So that eliminates the filters, short of the replacement caps being bad.
I think I know what is wrong with your set Jonathan! If yours is anything like mine the negative side of all the power supply filters does NOT go to chassis/ground. One of the first mistakes I ALMOST made with an RCA was to wire in a replacement filter with negative to ground. This would have been one BIG short. I don't have a schematic for your set, or my set for that matter. I just know this from hands on experience with an 8T-243 and my beloved TC-127. Both are wired like this. The whole filter section is isolated. Check your wiring. Its a VERY easy mistake to make assuming that the - side goes to chassis.
I got my transformer and have some of my own questions but to keep our issues straight I am going to put them on my own thread.
I hope this helps get the RCA going.
Tube out........