I replaced the resistors just thinking to be sure. I measured: 41V [R269] 0.013V [R267] 0.74V
Is it okay that i replaced them? I used 5.5K 1/4W....
Is it okay that i replaced them? I used 5.5K 1/4W....
Replacement with 5.5k is fine.
If I'm interpreting correctly, the 0.013V reading is the junction of R267 and R269? The problem lies there, I believe. Probe directly on the the two resistor leads on either side of this junction. I think you'll find different voltages; if they turn out to be the same voltage, probe at "bottom" lead of R269 that connects to the B- rail. There seems to be an open path somewhere between B- and the base of TR125.
If I'm interpreting correctly, the 0.013V reading is the junction of R267 and R269? The problem lies there, I believe. Probe directly on the the two resistor leads on either side of this junction. I think you'll find different voltages; if they turn out to be the same voltage, probe at "bottom" lead of R269 that connects to the B- rail. There seems to be an open path somewhere between B- and the base of TR125.
That's correct: 0.013V reading is the junction of R267 and R269. I measured this junction with the red lead of the multimeter and the black lead to the ground/chassis.
When i measure R267 at both sides with the multimeter i get 0.75V. For R269 it is 41.6V
When i measure R267 at both sides with the multimeter i get 0.75V. For R269 it is 41.6V
I still want to explore the issue of a possible 2.2 Ohm resistor across the amp output, but this is a separate mystery that can wait until audio is restored.
Given the likely broken trace near R267,269, also confirm intact connection to bootstrap cap C237.
Make sure you set bias pot VR101 to minimum before restoring power.
Good luck!
Make sure you set bias pot VR101 to minimum before restoring power.
Good luck!
I compared to the right channel; the junction of R267 and R269 should indeed be 21V. (at R268 R270 it is) Inspected the PCB very well for damaged leads but i don't see any. Measured from Base of TR125 to all points and no open connections. Could capacitor C237 47uF/25V be fault? Think i'm going change this one... I don't have a clue why voltages are wrong. Lack of knowledge 🙄
Yes, swapped C237 ; now there is bias! Thank you very much 👍👍 Never could have figured it out myself. Still have to test it, but it has bias voltage.
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If you see 41V on each lead of R269 and 0.75V on each lead of R267, then you should see about 40V between the two resistors leads that are ostensibly joined near C237. A shorted C237 wouldn't permit 41V to be present at R269. Probe from lead to lead and from lead to board trace to find the problem.
Maybe I'm not measuring correctly. Also find it difficult to understand instructions due to language and some limited skills. I'm going to read the conversation again tomorrow to learn from it and understand it better.
C237 tested / seemed not that bad. 46Uf vloss 2.1 esr 0.82. Nevertheless, the problem of the bias voltage has been resolved after replacement. I'm going to listen to it tomorrow and maybe put it together. Again thanks a lot!
C237 tested / seemed not that bad. 46Uf vloss 2.1 esr 0.82. Nevertheless, the problem of the bias voltage has been resolved after replacement. I'm going to listen to it tomorrow and maybe put it together. Again thanks a lot!