Well, there are many other things to consider too. Keep in mind the many possible scenarios : 1. Factory sometimes reserve the rights to modify change specs without prior notice and that the equipment you have can be a later version or an earlier one too. 2. The fact that the coloring is different can suggest that either at the factory the have mixed up the colors by mistake (in the old days transformers used to be made manually by individual people that could make mistakes too) and later on at the assembly line was picked up and then they connected the wires according to the output voltages rather then the colors. Now going back to the scenario. the 6.8V AC winding goes in place for the purple pair (marked on drawing) since it is obvious it would feed all incandescent lamps and some LEDs . The pair with the center tap is also obvious it can only go to where (GROWN/GRAY/BROWN) is shown on the drawing simply because the center tap is needed. Otherwise any other winding wont work. So what’s left now is the 68V pair that certainly needs to go exactly in place for the BLUE/BLUE pair )as per drawing shows) Now let me explain about it the 68V is indeed connected to the Power amp board (somewhat directly) but via the 2 fuses (F002 and F003) but the winding also needs to connect to the Power supply board (F-1434) because if you look on the drawing : it derives another voltage from it via the transistor TR001 (2SC1124) at the Emitter of it there will be a stabilized/regulated voltage that is also needed to the Power amplifier module F-1180F via circle 20. This voltage needs to be stabilized since it feeds the preamplification stage/part of the power amplifier module F-1180F
@ovi4 Ok so just to make sure I understand then the color code on the schematic compared to what the actual output on the wires are have been mixed up at the factory and the low voltage wire Blue 6.8v goes to the lighting and the Purple wire 54v goes to the Bridge/rec and the Brown Grey Brown goes to the 1434 board as it currently is.
@john-barron Things to consider here:
1. try not to let yourself carried away by the “confusing coloring used” try judging by the voltages and not by the colors. (it can be deceiving I know). Now going back to what you say why the highest voltage winding doesn’t go to the full bridge rectifier (4 diodes) as it should (logically speaking). … 🤔 …Well….there is way more to it to understand than meets the eye. Now let me explain, and this is to do with how various bridge topology works. You see a little theory is needed here. Full bridge rectifiers are of 2 different types and in this equipment of yours they are both employed but the resulting DC is different in each case. Let me clarify: the diode bridge (the one with four diodes) is one type of full bridge rectification and in this case is used to power up the Power transistors. This type of bridge uses only a simple 2 wire winding (no center tap needed) so the outputted DC voltage would be roughly similar to the AC inputted voltage. But there is a second so called full bridge rectification topology in which only 2 rectifier diodes are employed (in this case D001 and D002) instead of four but also a center tap is needed !!! and therefore even though the measured end to end voltage is in this case (according to your measurements 68V end to end) so quite a bit higher than the 54V measured for the purple pair the voltage level after rectification would be only “HALF” of the starting (end to end 68V AC) and this is easy to spot and measure just by looking at the filtering cap. voltage rating (C108) that is only 50V so the expected DC outputted voltage would be a fair bit less than 50V (the caps rating). So it makes sense that the 54V winding (no tap employed here) goes to the full bridge (4 diodes) place and the 68V (2 times 33.6V) goes to the other full bridge rectifier (that only employs 2 diodes but needs a center tap).
So John, I hope you understand now that there is indeed more to it than meets the eye … 😆 😉 😎
@john-barron In the old days having two diodes and a center tap was common practice and in turn they would save (not using another 2 diodes)… 😯 Now talking what’s after the rectification (if you examine that power supply board/schematic ) is quite a “long winded” but “cleverly put together” circuit/regulators that will output 4 different voltage levels marked on the drawing as: A, C, 18 and 19 (circled). And they go to feed various boards.
@ovi4 Yes it is all making sense now I see where after the 10DC1 bridge they are powering the two power transistors TR002 and TR003 where the emitter of tr003 supplies voltage to (A) and TR002 emitter is feeding three voltage dividers for (18), (19) and (C) and the 4 diode bridge 5B2 supplies both fuses and the collector of TR001 where the emitter is pushing power to (20) going to the 1180 pin 8C.
Thank you for the help. Now that I have a better understanding I should be able to calculate the voltages using ohms law for 18, 19, C and A.