The left channel is bad and when the power supply comes up initially the DC offset is detected and then the protection kicks in removing the AC to the main rectifiers. The if the relay were to stay energized for any length of time than it is the fuse may blow.
How did you know it gad to be one of these transistors?
Would it be just this transistor which causes this or are there more components which might have failed before or after the transistor failed?
You said the xfmr was humming and that means high current. We knew the power supply was OK so the next high current part(s) would be output transistors. Can you pull both output xsistors on the left side, it does look like TR410 is kaput. There could be other bad parts related to TR410 such as resistors and driver transistor, TR408
I am at work right now. I'll do that when i get home later this evening.
Not easy to get hold off those original Toshiba transistors here in Norway. Are there equivalent tr which are as good?
Not easy to get hold off those original Toshiba transistors here in Norway. Are there equivalent tr which are as good?
Specify the types of output transistors and drivers. You can pick up analogues ONSEMI or ISCEMI, Sanken, Sanyo ...
Focus on power, voltage and current, Hfe. It is good if the BJT is intended for audio applications, but this is not necessary.
Focus on power, voltage and current, Hfe. It is good if the BJT is intended for audio applications, but this is not necessary.
2SA663 Package TO3 :2SA663
Datasheet, Equivalent, Cross Reference Search. Transistor Catalog
2SC793 : 2SC793
Datasheet, Equivalent, Cross Reference Search. Transistor Catalog
For replacement, you can use modern plastic transistors. When installing, observe the following rules: thermal paste, thermal insulating gasket (mica, nomacon), insulating washers.
Datasheet, Equivalent, Cross Reference Search. Transistor Catalog
2SC793 : 2SC793
Datasheet, Equivalent, Cross Reference Search. Transistor Catalog
For replacement, you can use modern plastic transistors. When installing, observe the following rules: thermal paste, thermal insulating gasket (mica, nomacon), insulating washers.
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Yes, TR 408 measures 005,001,005 and 004 on the left side.
The TR 406 measures 692,707,979 and 1 onthe right side and
694,720,950 and 766 on the left side.
I tested some resistors R 409 is 973 kohm instead of 820. With a 5% that is too much off?
By pulling out both transistors did you mean i solder them from the circuit board?
Looks like TR408 is bad too. Measure all resistors connected to these transistors. Yes, desolder them from the board.
Hi, the transistors are of the circuit board
I checked about all of the resistors to be sure.
R 418 was physically broken and gave 1 as value.
R420+421 mesured about 40 Ohm instead of the 68 they should have been.
The big resistors R422+423 measured between 1,1 -2,8 Ohm instead of 47 but there is a small capacitor soldered between them on the back of the board.
R414 is in parallel with the thermistor so probably OK, you can remove it to make sure though. If you measure a questionable resistor value then remove at least one end of the resistor and measure again.