Sometime time provides perspective.
I had a successful procedure, and after a week of recovery, I removed the 10ohm resistors and C11, C14 decoupling caps.
Measured current as I brought up the voltage, and found that I had a problem with Q16 ,Q19.After replacing these transistors, and reattaching the caps and resistors, adjusted the bias and now the amp works fine. Sounds nice in fact.
djoffe: THANKS FOR YOUR HELP!
-Chas
I had a successful procedure, and after a week of recovery, I removed the 10ohm resistors and C11, C14 decoupling caps.
Measured current as I brought up the voltage, and found that I had a problem with Q16 ,Q19.After replacing these transistors, and reattaching the caps and resistors, adjusted the bias and now the amp works fine. Sounds nice in fact.
djoffe: THANKS FOR YOUR HELP!
-Chas
The problem is, that no triple EF output. The double EF overload the VAS, so there is no significant gain.
Sajti
Is this measured distortion, or can you hear the distortion (i.e. Have you listened to the amp with musical programme?)
I've only briefly listened with mp3 into my workbench speakers, and the amp sounded fine. Maybe I need to insert it into my high-end system using SACD?
-Chas
It sounds as though a few here seek to condemn this design , for whatever reasons(agenda)... :-(
What is your opinion on the Class A 50W+50W L10 from eBay?
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After running the amp for several hours I noticed that the driver transistors
Q16,Q19 (2SA1930/2SC5171, and these may not be genuine Toshiba)
run VERY hot
.
Using non-contact infrared thermometer, I measure 140-149 degrees F
(60-65 degrees C).
The heat sink is TO220 style with adequate size typical for PCB driver mounting.The drivers themselves are entirely plastic package(no metal tab ala
MJE15030 MJE15031), and are attached to the sinks using heat sink compound.
Any observations or suggestions for getting the driver temp down(without redesign)?
Thanks,
-Chas
Q16,Q19 (2SA1930/2SC5171, and these may not be genuine Toshiba)
run VERY hot
. Using non-contact infrared thermometer, I measure 140-149 degrees F
(60-65 degrees C).
The heat sink is TO220 style with adequate size typical for PCB driver mounting.The drivers themselves are entirely plastic package(no metal tab ala
MJE15030 MJE15031), and are attached to the sinks using heat sink compound.
Any observations or suggestions for getting the driver temp down(without redesign)?
Thanks,
-Chas
Measure the voltages across R6, 7, 23 & 27.
From these calculate the base currents to the outputs and the driver bias current.
Add these up to get the total emitter current of the drivers.
After you refit R20 & 22 you can calculate the base current of the drivers.
With Vbe and the gain of each driver and each output you should be able to see which semi/s is misbehaving.
From these calculate the base currents to the outputs and the driver bias current.
Add these up to get the total emitter current of the drivers.
After you refit R20 & 22 you can calculate the base current of the drivers.
With Vbe and the gain of each driver and each output you should be able to see which semi/s is misbehaving.
Did you test the amp with your high-end system ? I would like to have your opinion about it !
Thanks
Thanks
Let's hope there are still people following this thread.
Hasn't anyone compared the clone output stage and the original Marantz output stage?
The original had a triple Darlington output, and the clone has a dual Darlington output.
The first stage has separate and higher supplies too: +/-55v versus +/-48v for the output.
It should be worth a try adding a separate pcb board with the BIAS and triple Darlington right on the heatsinks.
The Marantz also thought of thiese amps to work bridged, which would probably cancel out noise and some distortions as a bonus.
Keeping the original passive parts values is something I would try too.
Hasn't anyone compared the clone output stage and the original Marantz output stage?
The original had a triple Darlington output, and the clone has a dual Darlington output.
The first stage has separate and higher supplies too: +/-55v versus +/-48v for the output.
It should be worth a try adding a separate pcb board with the BIAS and triple Darlington right on the heatsinks.
The Marantz also thought of thiese amps to work bridged, which would probably cancel out noise and some distortions as a bonus.
Keeping the original passive parts values is something I would try too.
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