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May I humbly suggest troubleshooting the circuit, instead of throwing parts at it?
If you had to replace output transistors, then always check the cement power resistors for opens. Always check that 180 ohm resistor between opposing bases - R101 or R201.
Always measure resistance between speaker terminal posts, looking for a shorted SAC187 triac there. A short across the output will usually make the output weak.
And any time outputs fail, always suspect the drivers - Q100, Q104. But equally important check the associate resistors for opens - R133, R112, R119, R134.
There is the dual diode on the heatsink, make sure it measures as if two diodes in series, and measure that at the ribbon header on the driver board to insure that the connection through the ribbon is intact.
Q102, Q103 are limiters - check the transistors, but also disable them during test by lifting CR106 and CR112 from circuit.
DO you have clean +/-15vDC on the op amps? Each channel derives its own 15v rails from the main V+ and V- with zeners.
Weak channel? Remove the compressor IC, U101. And check that the mute JFET is not stuck on. either remove it or measure its resistance while power is on.
Oh, and those shorted diodes at the input? DId you measure them once removed from the board? They are not across the input, they are between the circuit common "ground" and the chassis ground. See that lonesome resistor R130/R230 on the left side of the drawing? 47 ohms connected between ground and ground? Those are usually shorted across by connections to chassis at jacks. Point being that often that 47 ohmer will measure shorted, because both ends are connected together through chassis. And that means that in circuit, your "input diodes" will measure "shorted." Or asked another way, do your new diodes now measure as shorted once installed?
Since the thing is not blowing fuses, and may I assume there is no DC offset at the output? And we are no longer using anything like a bulb limiter?
If you had to replace output transistors, then always check the cement power resistors for opens. Always check that 180 ohm resistor between opposing bases - R101 or R201.
Always measure resistance between speaker terminal posts, looking for a shorted SAC187 triac there. A short across the output will usually make the output weak.
And any time outputs fail, always suspect the drivers - Q100, Q104. But equally important check the associate resistors for opens - R133, R112, R119, R134.
There is the dual diode on the heatsink, make sure it measures as if two diodes in series, and measure that at the ribbon header on the driver board to insure that the connection through the ribbon is intact.
Q102, Q103 are limiters - check the transistors, but also disable them during test by lifting CR106 and CR112 from circuit.
DO you have clean +/-15vDC on the op amps? Each channel derives its own 15v rails from the main V+ and V- with zeners.
Weak channel? Remove the compressor IC, U101. And check that the mute JFET is not stuck on. either remove it or measure its resistance while power is on.
Oh, and those shorted diodes at the input? DId you measure them once removed from the board? They are not across the input, they are between the circuit common "ground" and the chassis ground. See that lonesome resistor R130/R230 on the left side of the drawing? 47 ohms connected between ground and ground? Those are usually shorted across by connections to chassis at jacks. Point being that often that 47 ohmer will measure shorted, because both ends are connected together through chassis. And that means that in circuit, your "input diodes" will measure "shorted." Or asked another way, do your new diodes now measure as shorted once installed?
Since the thing is not blowing fuses, and may I assume there is no DC offset at the output? And we are no longer using anything like a bulb limiter?
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