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Old 12th Oct 2020, 11:23 pm   #8
mrrstrat
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Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Hallicrafters SX-25 Rebuild: New Mains Transformer Questions.

Great advice - but I sought it after the fact

The transformer is good - no ill effects and all voltages and other measurements are what I expect. The tube is toast though. All I have is some Type 83s and might venture to try one of them out after I correct the 5.0VAC CT connection..

Quote:
Originally Posted by turretslug View Post
You should most certainly not have connected the yellow/black to chassis! By doing so, you've subjected the rectifier tube and nice new transformer to a particularly brutal short test. Normally, the 5V winding centre tap is used as the point of HT (B+) DC extraction to the rest of the circuit- reservoir capacitor +ve, smoothing choke etc.

Often, the B+ is taken from one end of the rectifier heater winding as in your power supply circuit snippet - by providing a centre-tap in this case, Hammond have been kind enough to even up the distribution of the B+ current along the rectifier filament when using a directly heated rectifier like the 80 or 5R4.

Yellow to each end of the rectifier filament is correct. Fingers crossed that the transformer is still OK.
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