Depends what you mean by *danger* 
-- it might still pop, but it'll be a lot less likely.
The reduced current and voltage will not hurt the various circuit sections that it serves.
If a 150r isn't handy, a 180r or 220r or practically anything you have lying around that's 3 to 10x the original 33r, and ½ or ¼W. If you want to keep your finger on it, that's OK, too.
If you are at all worried about some or another danger that I haven't thought of, stick with the 1st suggestion and use the Ohms position on the DMM to find what other circuits might use the regulated +18V.
-- it might still pop, but it'll be a lot less likely. The reduced current and voltage will not hurt the various circuit sections that it serves.
If a 150r isn't handy, a 180r or 220r or practically anything you have lying around that's 3 to 10x the original 33r, and ½ or ¼W. If you want to keep your finger on it, that's OK, too.
If you are at all worried about some or another danger that I haven't thought of, stick with the 1st suggestion and use the Ohms position on the DMM to find what other circuits might use the regulated +18V.
as all the two modules are out of the board,
take this chance to check all the values of the Transistor, Diodes. resistors...
take down the details, its for future use, very useful for reference,..
compare the two modules, see if difference between them.
check the pins with resistance range.
********
take this chance to check all the values of the Transistor, Diodes. resistors...
take down the details, its for future use, very useful for reference,..
compare the two modules, see if difference between them.
check the pins with resistance range.
********
Is Q155 and/or Q156 very hot, after burning resistor? I mean if there is too many current, so resistor burn, Q155 also has burned with that current.
Did you using 1 watt resistor? Please use 2 watt or more? or series, two r245, 33 ohm resistor. So there will be 66ohm and 2 watt resistor. If it will burn again, q155 must be burned. Q155 in normal use, is very hot transistor.
D119, zener controls the voltage, Q155's current. if it burned (must be 18 volt over it), current will be uncontroled.
Did you using 1 watt resistor? Please use 2 watt or more? or series, two r245, 33 ohm resistor. So there will be 66ohm and 2 watt resistor. If it will burn again, q155 must be burned. Q155 in normal use, is very hot transistor.
D119, zener controls the voltage, Q155's current. if it burned (must be 18 volt over it), current will be uncontroled.
Time to follow that trace. Now you don't have to start at the regulator -- you can work away from where it connects to the pre/lineamps.
Any place you find 10.8V, disconnect it; or just find what is getting warm in that area.
Cheers
edit: Almost forgot: The power amp uses the ±18V rails, too. (Base bias for the cascode transistors of the input stage, and several other places.) So even though the power amp passes signal -- which is very good -- it isn't altogether in the clear.
Any place you find 10.8V, disconnect it; or just find what is getting warm in that area.
Cheers
edit: Almost forgot: The power amp uses the ±18V rails, too. (Base bias for the cascode transistors of the input stage, and several other places.) So even though the power amp passes signal -- which is very good -- it isn't altogether in the clear.
Last edited:
Since the provided schematic is incomplete, and blessed with errors (Did they run out of little dots in the drafting department that week, or what?), following the copper in the physical amp is the only way to go.
Stand it up on one end so you can get to the top and bottom alternately, and start tracing. When you find out where those 8 traces that go off-page to the right at the bottom of page 6 go, let us know. There surely are some likely suspects in that circle, since the ±18V and 12V regulators both head that way.
Cheers
Stand it up on one end so you can get to the top and bottom alternately, and start tracing. When you find out where those 8 traces that go off-page to the right at the bottom of page 6 go, let us know. There surely are some likely suspects in that circle, since the ±18V and 12V regulators both head that way.
Cheers
I came across C_320 and found it was a simplified design of C_352,
its easier to understand the structure of C_352 by studying this C_320 schematic.
Also C_372 is a higher version, though a bit complicate and voltages are different, the schematic layout is very clear. much easier to trace.
with help of these two schematic, hope it can help you to trace.
its easier to understand the structure of C_352 by studying this C_320 schematic.
Also C_372 is a higher version, though a bit complicate and voltages are different, the schematic layout is very clear. much easier to trace.
with help of these two schematic, hope it can help you to trace.