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MP573 Microphone preamplifier / Re: Troubleshooting MP573

« on: February 19, 2021, 02:29:39 PM »

thanks a lot for your quick help. you were right, i swapped c26 & c34. but still i don't get any voltage between TP2 & TP4. here are the resitances of the output transformer: 

yellow-orange: 23,8
red-brown: 19,4
blue-green: 20.9
violet-black: 21

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MP573 Microphone preamplifier / Troubleshooting MP573

« on: February 16, 2021, 07:11:52 PM »

Hey everyone,
I just buildt the mp573 but do not get it working yet. there is no voltage in between TP2 & TP4. in the following are the measurements at the reference points:

A: 2,5
B: 4,0
C: 22,5
D: 13,4
E: 1,9
F: 12,7
G: 0,0
H: 4,9
I: 0,6
J: 4,25
K: 4,25
L: 0,0

I couldn't find any bridged solder points, but I have to say, that there are two things that seem to be suspicious.

1.: in the diy-kit, the Resitors R31,R39,..., R68 (eight in total, labled as '47k' in the component list) were in my case 10k Resistors. I ordered new 47k resistors an attached them. there were also another five 10k resistors (R16,...,R56) in the kit, which i soldered in the correct place. Was it wrong to replace the Resistors with the correct value labled in the parts list?

2.: on the DI Board, there are three holes for the capacitors C34 (470n-100V). In the parts list it says, that it should be labled 'u47'. I wasn't sure, if I had the right part at first, and soldered it at the end. The capacitor I soldered is labled '4n7j100' and it only fits into the first two holes on the pcb. here you find a photo for better explanation: https://drive.google.com/file/d/1LbVpfQoVmGiiJJseUyKfa57sRqvknj2D/view?usp=sharing

thanks a lot for your help!
johannes