51

AB528 Microphone preamplifier / Re: First power on burned resistors

« Last post by Alaska on September 22, 2024, 10:16:49 PM »

Oh. Found something wrong.  Diodes on di board are not correct 🙄

52

AB528 Microphone preamplifier / Re: First power on burned resistors

« Last post by Alaska on September 22, 2024, 09:43:35 PM »

Ive replaced r33 and r34. What should I check before trying to power up again? 
I used my cranborne 500r8 before but think i will try my Lindell 510 500 rack this time as as the 500r8 is much more valuable.  
Could I rig up a 9 or 12v underpowered power supply from a wall wart just for testing point purposes before inserting into 500 rack?

53

AB528 Microphone preamplifier / Re: First power on burned resistors

« Last post by Alaska on September 22, 2024, 08:14:29 PM »

I checked and -91 is in q5, where it should be. Next?

54

AB528 Microphone preamplifier / Re: First power on burned resistors

« Last post by JPK on September 22, 2024, 12:08:25 PM »

Check that the power transistors Q5, Q6 are not swapped.

55

AB528 Microphone preamplifier / Re: Preampli AB528

« Last post by JPK on September 22, 2024, 11:57:40 AM »

Il faut vérifier direction et soudures de SW2, RLY3, D3, J2a pins 11-12, J2b pins 11-12.

56

AB528 Microphone preamplifier / First power on burned resistors

« Last post by Alaska on September 21, 2024, 05:09:16 AM »

Hello.  I was saddened to smell burning on first firing up my ab528.  I’ve built many 500 series and felt confident I understood and completed every step correctly.  The power was only on about 10 seconds and I see that r33 and r34 surely burned with possible discoloration on d7.  There is also a little melting on j2b.  The power Led never lit up. 
Every capacitor has correct polarity and magnifying glass couldn’t find any bridged solder spots or issues.  Please help!

57

AB528 Microphone preamplifier / Re: Preampli AB528

« Last post by Mateo_K on September 20, 2024, 01:48:01 AM »

Bonjour, merci, non en effet je n'entend pas le clic

58

CP4500 Stereo Bus Compressor / Re: No output when engaged

« Last post by JPK on September 19, 2024, 10:06:16 AM »

59

First Aid / Re: sk49 missing neoprene tubing and copper wire

« Last post by mikemorasky on September 18, 2024, 02:28:50 AM »

ty!

60

CP4500 Stereo Bus Compressor / Re: No output when engaged

« Last post by jd.musicology on September 17, 2024, 11:19:50 PM »

Found it! I got a little lazy on two of the U22 pins, re-soldered them and everything works now. Sounds great! Thanks for the fix.