1

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: February 01, 2025, 03:25:54 PM »

I found out the problem, I had reversed the polarity of D12, everything works fine now!

2

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: February 01, 2025, 10:09:41 AM »

The diode test between the V+ finger and test pin shows up at 0.6V, so I'm assuming it's fine. With all the components listed removed, V+ is at -1.18V, no component on the circuit board is getting too hot, all are cool to the touch, also there is no burning smell.

3

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: February 01, 2025, 09:38:09 AM »

But I was getting -15V on V- without having to remove the components, what I'm not getting is the +15V on the V+ test pin.

4

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: February 01, 2025, 09:31:18 AM »

After removing the said components, I am getting -15.25V between V- and oV.

5

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: February 01, 2025, 09:13:11 AM »

6

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: January 31, 2025, 02:51:14 PM »

The solder joints are all fine. D13 is also ok. L2 is 0.2 ohm, PTC2 is 1.1-1.2 ohm.

7

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: January 29, 2025, 05:21:42 PM »

no continuity between them.

8

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: January 28, 2025, 05:10:40 PM »

The voltage on V+ is -3.9V. As for the diode test:

9

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: January 27, 2025, 06:10:19 PM »

I did a continuity test on all the pcb connections, all were fine. The voltage on pin2 without U4 is -2.6V.

10

MP566 Tube microphone preamplifier / Re: MP566 not working.

« on: January 27, 2025, 04:17:04 PM »

1 -> -7.26V
2 -> -6.43V
3 -> -7.09V
4 -> -15.04V
5 -> -12.11V
6 -> -6.27V
7 -> -6.27V
8 -> -9.24V

11

MP566 Tube microphone preamplifier / MP566 not working.

« on: January 25, 2025, 11:56:58 AM »

I just built the MP566, I am doing the tests without the output transformer but I can't get any voltage on TP2, I checked the usual suspects, everything seems fine.