- Joined Feb 1, 2019
So i listened to music and sudenly the system just stoped playing with no power on the screen i thinked it is a fuse but when i opend it it wasnt.So i removed the output wires from the transformer and put mains in it and nothing happend i checkd the output voltage and there was 0 so i unpluged it from the mains and check the resisstance on the primary beacose the secondary was good but it was showing over limit on the multimeter so i smeled it and it has that smell when the insulation on the wire is burned.And you said you need the output transistors but there is no beacose everithing is integratet in the chip stk 459 and the transformer has a one winding with central tap that goes to a bridge rectifier with some filtering capacitor and that is powering the amp and the other goes to a different bridge rectifier with filter capacitors and that goes to a conector with two wires obviusly positive and negative and that goes to the equalizer of the amp.its realy old one and theres a lot of wires but the amp itself is realy simple.i reversed engeenerd it and it is realy close like the yakov send the picture and in mine it has some transistors when the conectors are conectedThe first post said "no resistance" on the primary. Do you mean zero resistance? Or do you mean no conductivity? And if you are not able to do any more checking how do you expect to be able to wind another transformer and have it work?
My guess is that you have an ohm meter with a single resistance range with perhaps 1500 ohms mid scale, and a low resistance shows tha same as a short circuit.
So at this point you are going to need to do some circuit tracing and see what the two secondary windings feed. If the one set is just for the lights, then you are in luck.
If you can tell us the type number of the output transistors then we can figure out the voltage that is needed for 80 watts output.
One more thing, which is that the numbers in the picture are very hard to see.
SO please read them and post what they are , and THAT may provide us with some useful information.
What were you repairing on the amplifier before you found this problem?
AND, REALLY, if you can provide us with the type numbers of the output stage transistors than quite probabkly we can give some worthwhile assistance.