Mackie HR624 mk2: Dead Mackie HR624 MKII measurements... check my work?

Tue, 23 Dec 2025 19:50:12 -0700

I have a dead Mackie HR624 MKII part of a pair I got for free. The other one powers on, but emits only static.

I want to use this as a learning opportunity to do test measurements and diagnosis and hopefully fix the problem.

Schematic: https://www.audioservicemanuals.com/m/ma...

I am starting with the dead monitor first. Like I said, dead, no power light, no sound. Fuses checked and are good. A visual inspection does not reveal anything obvious. no leaking, bulging capacitors. no shorts or burnt parts of the board. the grounding wires look ok at the connection point, no corrosion, but maybe they could be cleaned up anyway.

I did a Transformer AC Output Test and got ~31V AC from the center wire to each outer wire and ~64V AC between the two outer wires, so it seems power is being correctly delivered to the main circuit board.

Next I did a Main DC Power Rail Test and measured 0V DC on both test points.

So that led me to the bridge rectifier. I got the correct forward voltage drop (~0.6V) and an open circuit reading in reverse.

So I did some point-to-point continuity tests

AC Path (Transformer to Rectifier): PASSED. There was a good connection.
Ground Path (Center Tap to GND): PASSED. There was a good connection.
Positive DC Path (Rectifier + to Capacitor C39): FAILED. Showed "1" (no connection).
Negative DC Path (Rectifier - to Capacitor C48): FAILED. Showed "1" (no connection).

I'm guessing there is a physical break in the copper traces on the PCB? If so, reflowing that is beyond my knowledge and skill probably. But I could do small jumpers?

Or am I misunderstanding the result of the measurements?

I can share pictures if anyone can help me see the issue the measurements are pointing towards. But now i feel a little over my head.

Thanks.

⟐ Answer accepted December 23, 2025 at 19:50 MST

Mackie HR624 mk2: Mackie HR624 mk2 won't power up (very often)

Mon, 08 Feb 2021 13:50:24 -0700

I’m having what seems to be a fairly common problem but the common fix didn’t work. One of my HR624 mk2 monitors won’t come out of standby (you could think of it as not powering on), except on one occasion, when it worked fine. I’ve carefully replaced c65 (ok, I did it twice because I wanted to be sure I didn’t cook the first replacement cap and was super careful the 2nd time) and used Deoxit on the main standby switch and the other pots and switches. I get the red LED flash when AC is switched on, and then again when it’s switched off, but no good-to-go white - except once. It worked fine on that occasion, except possibly with some loss of volume (though I might have been imagining that). I haven’t been able to coax it out of standby since that time.

Any other easy fixes to try? Since there does seem to be a common problem with c65 going bad, I am tempted to simply replace all of the caps on the board - there aren’t that many. If that’s the next step, does anyone have a parts list they could share to make for easy ordering? Thanks in advance!

Update: I’m not enough of an engineer to figure out hot to do this, but if there’s a way to bypass the standby feature entirely and have it just power up when AC is applied this would be great as I have the whole monitor rig (HR 624s + sub) on a power strip anyway.

⟐ Edited by author February 08, 2021 at 13:50 MST

iFixit - Answers With Device "Mackie HR624 mk2"

Mackie HR624 mk2: Dead Mackie HR624 MKII measurements... check my work?

Mackie HR624 mk2: Mackie HR624 mk2 won't power up (very often)