mackie mixer diode replacement

[samuel497]

Hi All

Im new to this forum so please be gentle  lol

I am attempting to repair a mackie audio mixer pro fx v2  as there is no input in channel 3

I purchased a pair of smart tweezers for in circuit testing to save removing from  pcb board although im not entirely sure I trust the readings.

It is showing a short in some of the diodes DL4148 near the preamp so I have decided to order them and a pair of heated tweezers to make changing them as painless as possible.


I contacted mackie and got the data sheet for the part number and it seems to be very difficult to get the exact spec of the diodes needed and wondered if someone could point me in the correct direction of the correct part or confirm the diodes I ordered will be ok.

I have attached the diode spec I got sent from mackie and will post a link to the diodes ive ordered they are very similar in spec but the surge current is different they have the same reverse voltage etc.

link to ordered diodes https://www.switchelectronics.co.uk/ll4148-switching-diode-150ma-100v

Any help would be much appreciated.

thanks in advance

[floobydust]

They are the same, it's just the surge current spec either has a typo (Changzhou Changyuan Electronics "=1s") while other reputable makes are 1usec, for IFSM of 2A. IFSM 500mA is under 1 sec.
The diodes fail if there is a phantom power surge coming into that mic channel, best to not hot plug.
If you find a diode instead went open-circuit due to the overload, it will damage the op-amp they are protecting.

[TheMG]

That diode is nothing special, just a MELF (surface mount) version of a 1N4148 which is a jelly bean part. While there might be some small variations in specs between manufacturers they should be quite similar. I doubt the exact specs matter much in this application, any 4148 diode from any manufacturer will probably work just fine.

[samuel497]

Thanks the main thing I was worried about was matching the reverse break voltage as if its exceeded then the diode becomes destroyed or at least that's what the told me on my HNC course.

Thanks

[samuel497]

Hi Again

I have replaced 5 faulty diodes and now channel 3 is back working so defo making progress

I have one other issues to try and solve.

Channel 1 is noisy when you move the fader up it sounds like an increasing loud static noise even if no mic connected.


Any ideas?