With the power off, can you trim the resistance of RV101? Are the values of R122 and R123 still what they are supposed to be and does TR105 behave normally?
Yes, RV101 can be trimmed. Tr 105 is defective (CE short), and R122 was open....
R123-127 are ok. Output transistors seem ok too.
As I have no replacement for Tr105, I need to order some.
I have a 60V 0,7A pnp, but without heatsink (“star”)..
R123-127 are ok. Output transistors seem ok too.
As I have no replacement for Tr105, I need to order some.
I have a 60V 0,7A pnp, but without heatsink (“star”)..
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Update: I replaced tr105 and r122 and the amp worked again. However, the noise still persists.
After that I replaced tr102, tr101, mr100/101, c105. All without effect, the amp works but with very audible, wide spectrum noise.
Bias and half-rail are set correctly.
The attachment shows the points where I measure noise (black dot), and where the signal is clean (“lasso”).
The “V” indicates replaced parts.
As said, the other channel sounds perfect.
Any guidance is welcome. Next weekend I will continue working with the amp.
After that I replaced tr102, tr101, mr100/101, c105. All without effect, the amp works but with very audible, wide spectrum noise.
Bias and half-rail are set correctly.
The attachment shows the points where I measure noise (black dot), and where the signal is clean (“lasso”).
The “V” indicates replaced parts.
As said, the other channel sounds perfect.
Any guidance is welcome. Next weekend I will continue working with the amp.
Attachments
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Update: replaced tr100, 105, 106 and 107 for the “official” replacement parts, however, without results.
Still noisy, while the other channel is dead quiet.
The noisy channel can be adjusted perfectly (bias and half rail).
Any suggestions for another source of the noise?
Still noisy, while the other channel is dead quiet.
The noisy channel can be adjusted perfectly (bias and half rail).
Any suggestions for another source of the noise?
I fixed one of these many many years ago for some noise problem and it was a small ROE electrolytic, can't remember which one now though.
There are only 4 electrolytics per channel, so that’s not that much work.....might try that. Thx.
Found it!
C101 was the problem! Replaced for anew 330 uF (was 470 uF), and the noise is gone.
Now my 34 preamp is faulty (very low output, mono, loud clicks when applying the filters etc).
I open a new topic for that.......
C101 was the problem! Replaced for anew 330 uF (was 470 uF), and the noise is gone.
Now my 34 preamp is faulty (very low output, mono, loud clicks when applying the filters etc).
I open a new topic for that.......
excellent and that that could well be the same one I had.