Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Just thought I'd tidy this up.
I didn't complete this fix as it only cost $4.95 to get another unit from China. A little annoyed with myself at not sorting it.
The new one had the same number of connections and was wired the same way as I described above. No colour coding on the wires to copy though.
I guess I could have tried dozens of combinations until I got one to work (provided the opamp wasn't blown) but honestly I couldn't spare the time. Especially as I...
Ozyris
Member
Last Activity: 09-27-2014, 07:21 AM
Joined: 04-21-2014
Location: London UK, returned on the millenium
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Quick update: All four speakers still working 100% and sounding awesome! Can't stop thinking about acquiring another two to fix. Lol. Don't know what I would do with them...spares?Leave a comment:
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Re: Alesis m1 active mk2
Wonder how Strobe7 is getting along...Leave a comment:
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Re: Alesis m1 active mk2
Hi Strobe7. I would suggest taking a read through the thread started by firespace on precisely this topic. There is a huge amount of info there on fixing these very nice speakers, including some contributions from some rather clever chaps, including LuigiDJ and Khron666. Some modification to the layout of these power amps will prevent the problem happening again. Good luck and keep going till you've got it sorted!!Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Aha. Thank you stj. I learn so much here. Sounds expensive. Relative to the preamp...Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
So, as the power wire is often red on such circuits as your post suggests, then 1 or 2 may well be the 9v+ connection. Looking at my diagram it seems unlikely that it would be 1 as it doesn't make sense to me to have substantial voltages all over the pcb (relatively speaking). It seems more likely to me that 2 would be 9v and would go only to the opamps.
I agree that it is probably a dual opamp similar to the TLC074 or LM741.
Connection 1 may well be the signal output or input. Red...Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Hello stj. I am wondering as to the meaning of the word "nitromors"?
Prop1. Thanks for taking the time to think about this. Just to recap - there are two tone controls, one for bass and the other for treble, each needing three wires. The unit is a 2-band EQ preamp.
The pickups are connected to the blend pots which are not involved in the preamp other than supplying it with a pre-blended signal through one wire.
Two wires were previously connected to the volume...Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Hello everyone and thanks for the input so far. Just had to dash off to Heathrow airport to fetch someone but back now.
Thinking in the car that my last diagram needs a tweak. Every one of the coloured junctions actually represents one of the wires coming out of the board. So here it is with that idea clarified.
It may not help anyone else's thinking but I think it helps mine.
It also occurred to me that it is probably only the hidden opamp that...Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
...I am thinking that 10 might be the ground?Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Hello Prop1! Thank you for diving in. Yes indeed, it may well be not worth the trouble. But sometimes puzzles are fun. Check out my repair job on my Alesis M1 MK2 Active Monitors for a little insight into that.
I am afraid there is no further identification on the guitar.
Regarding the pots etc they are all there. I have good clean signal on the output of the blend pots. That's where the board will get its input signal from.
Here is my "scribble" layout...Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Hi Steve. Thanks for getting stuck in! Its a Crafter Cruzer four string (no snide remarks please = not mine!). No other identifying marks. I doubt this preamp is original.Leave a comment:
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Re: Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Okay, so here is the table of measurements. As I suggested above, these are really very approximate. Where there is no number there is no measurable voltage or alternatively infinite resistance. To measure voltage I connected a 1.2V AA battery in series with my meter, then connected across pairs of wires.
I will post a scribble diagram of my interpretation of this table shortly.
Thanks!Leave a comment:
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Bass Guitar Pre-Amp - Assistance required from local geniuses please!
Greeting fellow tinkerers!
So I have this bass guitar to fix. Someone tried before and was unable to to do it. l Between us I think we could make a darned good effort!
The preamp has been disconnected (I believe its a replacement that was not wired in properly). I have been unable to source a wiring diagram or even locate a supplier to ask for the connection schema. So its down to detective work.
First obstacle: The board itself is hidden within an impenetrable layer of opaque black epoxy. All we have to go on are the wires coming out of it and the... -
Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Well, I am feeling good about it all. It was a huge learning curve. Not having a background in electronics I am pretty chuffed.
My original two monitors are either side of my production desk. They are my dedicated recording monitors and are connected to my Soundblaster Elite Pro (old I know but still an amazing card/breakout box). They work 100% now and as you know sound awesome.
The second pair is above them and slightly wider apart, tilted downwards. They are hooked as the main speakers into a 7:1 Yamaha...Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Mr Khron666 sir...I believe I was referring to your very own quotation of elegance? An "elegant solution" I believe it was...partly emulated by my far less able self. A tribute perhaps?Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Aha. Thank you. Loss of elegance there.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
What will I notice different about the sound? Or is it to do with longevity? Heat issues? It seems to work fine. As far as the technical things you said above, I have no idea what that means. I am but a lowly musician.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Okay - so this is what the final layout looks like now after pre-emptive surgery. The underside of the board doesn't look any different.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
I am just busy doing the elective surgery. Wondering why I can't just swap C8 and C14, provided I get the polarity right on C8. Is there any threat to the little ceramic from the two big resistors?
Btw, I have already tried it and of course it works fine. The circuit diagram says it will. Just wondering about the heat. I have the resistors bent away from the ceramic and of course away from the large caps.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
What happened to your first pair?Leave a comment:
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