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Digital Deaigns M4A
Digital Deaigns M4A
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Old 19th October 2020, 06:27 AM   #31
Perry Babin is offline Perry Babin  United States
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Location: Louisiana
Which end of D82 reads 0 ohms to the negative rail?

Remove C83 and see if the gate voltage changes.
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Old 19th October 2020, 06:37 AM   #32
caraudioguy2100 is offline caraudioguy2100
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Striped side of D82 has 0 ohms to the negative rail

And if I remove C83 I get -3.90 volts on the gate
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Old 19th October 2020, 06:42 AM   #33
Perry Babin is offline Perry Babin  United States
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Install another cap there to see what the voltage goes to.

Was the positive terminal connected to the negative rail?
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Old 19th October 2020, 06:51 AM   #34
caraudioguy2100 is offline caraudioguy2100
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New cap and the voltage is at -4.70 volts black probe on negative rail.
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Old 19th October 2020, 07:01 AM   #35
Perry Babin is offline Perry Babin  United States
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Join Date: Nov 2003
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Have you given up on finding a K30A?

The diode D82 is a 5v Zener. That's limiting the gate voltage to -4.7v. That may not be enough to get a J111 to switch off. Replacing that diode with a 10vZ and installing the J111 with the correct pin configuration (don't let the leads short) may allow it to work.

If you try it and it doesn't work, post the DC voltage on all 3 terminals of the J111.
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Old 19th October 2020, 07:03 AM   #36
caraudioguy2100 is offline caraudioguy2100
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Can’t find a K30A

I’m am not a fan of using NTE parts but the local shop has a nte cross for the transistor


Wondering what your thoughts are on this ?
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Old 19th October 2020, 07:05 AM   #37
Perry Babin is offline Perry Babin  United States
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Join Date: Nov 2003
Location: Louisiana
It could be an option.
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Old 19th October 2020, 07:30 AM   #38
caraudioguy2100 is offline caraudioguy2100
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I looked through my junk boards and what are the odds I found a K30A in an old kenwood amp .

Replaced it and amp has audio .

Thanks for helping me with this repair greatly appreciate it
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Old 19th October 2020, 07:39 AM   #39
Perry Babin is offline Perry Babin  United States
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Join Date: Nov 2003
Location: Louisiana
That may be useful. The 2SK30A may be available from pacparts or east coast transistor as JVC or Kenwood parts.
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