Sorry, as far I know, the dock was sold long time ago.
If I'm not mistaken, those docks can be bought from ebay for a reasonable amount, thus getting one just for the firmware files does not sound that bad....
madan1
Badcaps Veteran
Last Activity: Yesterday, 06:36 PM
Joined: 11-27-2016
Location: Sofia
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Download the service manual for mackie SRM550, it uses the same IRS amp driver and you can use that manual for reference.
The audio signal is on pin3 of the IRS ic (probably you have already noticed that in the datasheet). If you do not have a signal generator, you can use tone generator app for a phone/pc and connect it to the audio inputs. Probably the crossover is around 2-3khz, so anything below 1khz should be usable.
The problem with the coil is that the whole unit is mounted on a large vibrating noise maker and heavy components tend to crack solder joints. Here is one of the...Leave a comment:
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Probably just Vcc for the IRS (referenced to negative rail). For instance - https://www.infineon.com/assets/row/...tasheet-en.pdf...Leave a comment:
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How many irfb4227 mosfets are there? 2 or 4?
If 2 - then it s half-bridge (single audio signal and ground), 4 - full bridge (two inverted audio signals).
Did you check the solder joints of the big coil? Youtube is full of videos with cracked joints exactly on that heavy coil.
What is the mosfet driver? IRSxxxx or something else?...Leave a comment:
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Most likely it uses IRS of some sort for the IRF drver/d class amp.
Find the exact IRS model, download its datasheet and check the application schematics.
By the way, mackie DLM12S uses the same IRFB, so you might be able to use its schematics for reference.
Verify that the main power rails are fine, but before doing anything, check the big heavy components for cold solder joints (especially the big coil on the LF output)....Leave a comment:
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You sure about that?
On that image I can see at least 4 other inductors, which most likely belong to power rails.
Do the DAC, ADC and the RCA amps have power?...Leave a comment:
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That's the rabbit hole I was talking about - first cleaning pots/switches, then capacitors, then dry solder joints, then bad wires, then.. and here is the restoration. Unless something brittle and expensive gets broken and then it turns into a "nice project for someone who wants to invest time and money".
On such old units there are way many parts that might cause that issue, and the best way is to follow the audio signal with a scope and pinpoint the exact cause. Shooting in the dark by changing suspicious components can cause even more issues....Leave a comment:
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There should be an input/preamp board, which processes and splits the signal for the LF and HF amps. Check if there is LF signal coming from that board.
Also, what amps are used for HF and LF?
Post some more photos of the amp and preamp boards (both sides).Leave a comment:
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Damn, if this is the unit, I wouldn't touch it unless I'm willing and prepared to make full restoration.
If you are planning to sell it, better sell it like that and let the new owner repair it. Just cleaning the pots might not fix the issue, but even make any further repairs more expensive....Last edited by madan1; 06-10-2026, 04:04 AM.Leave a comment:
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Thank you. That's the first time I'm seeing this feature so I was not sure if an admin is checking the posts or they automatically go in the bin....Leave a comment:
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One more try to post the links to the noise audio and the schematics (remove the extra spaces)
Here you can hear the noiseHere are the schematics of the pre-amp boardCode:mega . nz / file / MdQBwBLA#S8ojJG4Pk_qftWMznXTv3SXh5cGqc6jYzkzjnc4X2-M
Code:mega . nz / file / ZZJi1bpB#j1zcbK9Ko99PGp7hW-O91sLcpJZM6S5_w6Qu_yQqB6E​
Leave a comment:
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Looks like the forum does not like external links, so I'm posting them with extra spaces:
Here you can hear the noiseHere are the schematics for the pre-amp boardCode:mega . nz / file / MdQBwBLA#S8ojJG4Pk_qftWMznXTv3SXh5cGqc6jYzkzjnc4X2-M
Code:mega . nz / file / ZZJi1bpB#j1zcbK9Ko99PGp7hW-O91sLcpJZM6S5_w6Qu_yQqB6E
Code:Here you can hear the noise mega.nz/file/MdQBwBLA#S8ojJG4Pk_qftWMznXTv3SXh5cGqc6jYzkzjnc4X2-M Here are the schematics of the pre-amp board mega.nz/file/ZZJi1bpB#j1zcbK9Ko99PGp7hW-O91sLcpJZM6S5_w6Qu_yQqB6E
Leave a comment:
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Hissing/noisy Mackie SRMv3 speaker
Good day.
I'm troubleshooting a mackie srm 350/450 V3 speaker, which makes a high pitch noise.
The amp plate unit consists of quite a standard power amp section, which is used across multiple other mackie models (switching mode power supply + TDA8954 for the LF and TDA7294V for the HF and of course the auxiliary power rails - +/-15V, +12v) and an input/pre-amp board.
I also have an older mackie speaker so was able to switch boards and the analog only input/pre-amp board does not hiss with any of the power amps and vice versa - the V3 preamp board is noisy...Last edited by madan1; 05-31-2026, 08:50 AM. -
https://elektrotanya.com/showresult?...a=All&kat2=All
Check the bridge/stereo switches. Then check the connections between the switch pcb(s) and the other boards and the volume pots.
edit:
red - bridge signal pathway
blue - stereo signal pathway
In bridge mode both amps are fed the same audio signal, but for one of them the signal is inverted....Last edited by madan1; 05-19-2026, 02:05 PM.Leave a comment:
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I just used google - searched for "[top label] datasheet", then [top label -1 character], -2 characters] and so on. Then switched to the bottom label and got lucky with literally the first result. Then just needed to confirm that this is the correct IC by comparing the datasheet pinout with the actual board.
By the way, there are some databases, which from time to time get the work done (just google "ic markings").
I heard that the AI bots also seem to help, but I haven't had success yet, probably I'm not using the correct bot..
And here is a video from David...Leave a comment:
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pins 1 and 2 (sw) are bridged , pins 8 9 an 10 (AVIN and PVIN) are also bridged .
pin 7 seems to be ground
pin 5 (SYNC) is also connected to ground, which is a valid option for the LMR
pin 3 (boost) looks like connects to a diode and a capacitor, which also corresponds to the application schematics for the LMR (can't really see where the other end of the diode connects, but the cap seems to be connected to pins 1,2/SW )
and the final clue - according to the specs sheet, LMR12020XSD has a part marking of L284B.
So, if it was me, I would already be looking from where...Last edited by madan1; 05-14-2026, 03:21 PM.Leave a comment:
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Can you remove it and make a photo of the pads? Or draw a schematic of the pinout and which pin to what is connected?
By the way check if it might be this https://www.ti.com/lit/ds/symlink/lm...=1778730514337Leave a comment:
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And just to update the thread - the folks from EV were good enough to label the connector pinout, but then somebody decided to put there the serial number sticker.
The good news is that the amp does not require any communication with the preamp/input board to operate. Also, the amp turned out to be fully operational - no repair needed even though it was listed as faulty.
Still, there are two atmel controllers - one on primary and one on the secondary sides.. probably they are doing some power monitoring/management, but luckily they do not speak to the preamp board.
By...Leave a comment:
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Liquid rubber, silicone gasket, etc.. those should be fine for repairing the foam. Of course re-foaming would be best.
And get a grill.Leave a comment:
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opamp no gain
Hello everyone.
Do you have any idea why the following design shows no gain (it is supposed to be audio "preamp")?
For instance, on the input I have 100hz 2Vpp and on the output I have 100hz 2vpp on each end referenced to ground and 100hz 4vpp when scoping between the two outputs. Thanks in advance.
P.S. After checking the item's manual and comparing it to other similar items, it looks like this "preamp" is only for inverting one of the outputs and no gain is mentioned at all. So I guess it was me just having wrong...Last edited by madan1; 04-14-2026, 03:33 PM.
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