As illustration - noise caused by two transistors Q1 and Q3 (compare this to the traces in earlier posts):
What are the substitutes for them?
The clearest indications of big improvements are the RMAA tabel.
Hugo
The clearest indications of big improvements are the RMAA tabel.
Hugo
Sub for 2sk30 is 2sk209, need an adapter. 2sa725 are known to go noisy over time, replace with ksa992
In this application is there any difference between 209 and 209-GR?
And any recommendation for a commercially available adapter?
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use the same Idss ranking that's on the original, you can compare the two specs to be sure.
in the old days 🙂 they used paint to identify Idss and hfe ranking, that's where the suffixes that they use today come from, unique to Toshiba,
BLue,Yellow,GReen etc.
2sk30 is in the old package, it goes way back.
I have read on a few occations 2sk30 were changed to solve a noise issue but usually they change 2sk30 and 2sa725 together so not 100% sure its the 2sk30 by itself. change the 2sa725 first, if that does not do it, change the jfet. good luck.
in the old days 🙂 they used paint to identify Idss and hfe ranking, that's where the suffixes that they use today come from, unique to Toshiba,
BLue,Yellow,GReen etc.
2sk30 is in the old package, it goes way back.
I have read on a few occations 2sk30 were changed to solve a noise issue but usually they change 2sk30 and 2sa725 together so not 100% sure its the 2sk30 by itself. change the 2sa725 first, if that does not do it, change the jfet. good luck.
TO18 cases usualy have the markings on the sides.
They could have been wiped off by cleaning.
Hugo
They could have been wiped off by cleaning.
Hugo
Must have been a well done repair. It’s been worked on before. red wima caps, ecaps are not original.