[rob@roblanter.com]

Hi JP,

R14 and R15 started to burn up when I inserted the SK25 DOA during the testing phase after the build. All the voltages checked out before I inserted the DOA.

I sent you an email asking for replacement parts.

Thank,

Rob 

[JPK]

99% of the issues: https://www.soundskulptor.com/forum/index.php?topic=9.msg9#msg9

[rob@roblanter.com]

Hi JP,
 
Is there a reason why a defective SK25 DOA would affect resisters R14, and R15 on the 501 Passive EQ? As soon as I installed the SK25 DOA, R14 and R15 started smoking. 

Thanks,
Rob

[JPK]

Yes. These 2 resistors are inserted in the +&- supply rails of the DOA.

[rob@roblanter.com]

I was trying to be very careful when I built the SK25 since it was the second one I had built. Can you tell me what I might have done wrong on the SK25 to have caused R14 and R15 on the 501 Passive EQ to burn up?

Thanks,
Rob

[JPK]

• make sure R1 is not touching the vertical PCB and the diode D5,
• check you didn't flip the power transistors Q9-Q10,
• check that the 4 solders on each vertical PCB are making good contact,
• check you didn't reverse the LED (it must light up),
• check you didn't swap D4 (Zener) with one of the 1N914.

[rob@roblanter.com]

My problem is solved. I had flipped Q9 and Q10...thanks.

I have another post with some other issues with the EQ501 unit.

Rob