Re: Repairing Alesis M1 Active mk2 Monitor Speakers
After touching gate and source both ways on Q1 are 0,57v so still good?
But I replaced already all parts and placed a FR107 on D16.
And speaker working again!!! That was a quick one!
And probably replaced too much, I guess only D1-4 and D16 where the problem...
Micwest
Member
Last Activity: 12-09-2017, 09:53 AM
Joined: 08-29-2017
Location: Amersfoort
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
D1-D4 also shorten outside the circuit, D16 shorten outside.
Q5 and D6 looks good outside
Even Q1 doesn't looks that bad as inside. Diodetest D-S give 0,2v and 0,575v the other way(which is propably not good but not total shorten). All other way of diode measuring are OL on Q1
D16 is a superfast MUR160 600v 1A. I don't have that way spare, wil a FR107 do?Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Okay, repairing M1 620 number2. Issue blowing fuse, no visual damage, first time parts will be replaced.
I measured most transistors and diodes and found the following components brocken:
D1-D4: shorten
Q1 shorten
D16 shorten
D6 and/or Q5(between b-e) shorten (will measure again as soon as I dismounted them, measurements still on board)
I would like to replace these parts and preventive C8 and R3&R4 (higher value and will mount them on backside of print for heating issue....Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
So... measured some things...
Q7 measure shorten. Replaced and working!!!
My first 620 repaired! Thanks very much for the help!!!
Up to the second one. That one blown fuses also, but no visible damage. I've learned a lot, so will first start by myself and measure some things and will come back with my conclusion :-)...Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Swinging between 0 and 1,9 volt...
No sorry, wrong side of R9.
Hard to see, between pin 5-8. My autorange meter is not quick enough, so swinging from 0 to OL, max seen 42volt, swing freq 1-1/2Hz? or this is limit of my meter?...Last edited by Micwest; 11-18-2017, 05:18 PM.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
I replaced Q3,Q4,Q5 and C8 by the NCC KY serie.
But still not powering on.
Voltage on U1 pin 5-7 swings between 10-15 volt...
I'm lost again, some tips to measure now?...Last edited by Micwest; 11-18-2017, 03:52 PM.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Is Elna RJH serie good?Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
And what should I use for value for C8 220/330uF 35/50volt? (orginal 220uF/35v/105C)Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Of course, a low-ESR cap, why didn't I think about that ;-)
I'm wondering about all the knowedge you have about this, I don't have any idea were you're talking about. In some cause the value doesn't matter so much, in other causes you need more details then ever given in the documentation. Without help of guys like you I never could fix this, so I'm very pleased with all the help!!!
Do you think this wrong choosen cap could be the course of my problem(low voltage on U1)? I will exchange Q3+4, Q5 I don't have...Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
I have Q3&4 (2N5401&2N5551) available so just have a try by replacing?Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
C8 is replaced by(sorry China again ;-)):
[url]https://nl.aliexpress.com/item/10pcs-330uF-50V-Japan-ELNA-RJ3-Series-10x20mm-50V330uF-Audio-grade-capacitor/32780662346.html?spm=a2g0s.9042311.0.0.lsgS44[/url]
And no sorry, I don't have a bench power supply.
Q4 was damaged and is replaced. In my speakers Q3&4 are resp. 2N5401 & 2N5551
Is there a way to measure these?Re: Repairing Alesis M1 Active mk2 M...0.lsgS44[/url]Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
R3+4 ok, both 47k and about 157v over each. (Orginal 24k)
C8 looks good(don't know how to measure) and replaced again.(330uF/50v)
D5 ok, R5 (5ohm) ok.
U1 was a 3842 and is replaced 2 times by a UC3842ANLeave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Okay, mosfet replaced (Q1 and Q2, chinees versus, sorry), again D1-4, C1+2(I don't know why). First issue solved: fuse won't blow out anymore, but no audio, no powerled. Between below D3/4 and above D1/2 I measure 318V=. U1, between 5 and 7 1,1v. On connector J5(not attached during measuring) I don't measure any voltage between pin1 and others....
so any suggestion what to measure/replace more?...Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Oh, okay. I thought 99% of all this stuff is coming from China, also the ones I buy here in local shops? Aren't they the same?
And i thought these mosfets are 'just' for the powersupply unit, so won't impact the quality of the speakers. But if they are doing a hardjob in this part, I will reconsider to buy some in NL...Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Okay thanks, your assuming is right, so mosfets(IRF840's) ordered in China, so take a while again, but 30x cheaper then buying in my own country(the Netherlands). In China 10 pieces for €1,38 including transport :-)))Last edited by Micwest; 09-25-2017, 11:47 AM.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
I guess that are Q1 and Q2? They look normal. I measured on board the resistance(l=left, m=middle, r=right pin)
Q1: l-m 77kohm, m-r 0 ohm, so broken?
Q2: l-m 660kohm, m-r 660kohm, l-r 10kohm, good?
I measured also my other 620, same problem(fuse), nothing burned or replaced yet
Q1: l-m >>>, m-r 0,6 ohm, so broken?
Q2: l-m 120kohm, m-r 100kohm, l-r 10kohm
In the first speaker Q1+2 are FTP08N50, IPS YHD3, HB001S
In the second FTP08N50, IPS YGH2, HB014S
They all look original...Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Replaced:
D1-4; R5; D5; U1; R18; D15; C35; R11; Q4(2N5551); R15 (see attached scheme)
But still fuse is burning out directly (without any other visible damage)
What can/have to replace/measure more?...Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
Okay, all broken and needed parts are ordered and hopefully I receive everything this week, so I can rebuild this weekend. Thanks for the help so far.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
The 'hot' 2watt R3+4 should be 47k conform the scheme, if I measure them they are 38k and the colorcode(red,yellow,orange,gold) tell they should be 24k !? I would like to replace them, but for what?
R5 is conform scheme 10 ohm, conform colorcode 5,1 ohm. R18 is conform scheme 100 ohm, conform colorcode 500 ohm. The scheme is officially of the MKII, mine are 620's, allthough the number of the print is the same, maybe the 620 use different values? (Also mine U1 is uc3842 io uc3844, R9 20k io 6k2, Q3 2N5401 io 2N4401). My...Last edited by Micwest; 09-10-2017, 01:44 AM.Leave a comment:
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers
I measured in diode-test both ways;
D6 0,5;>> inside board
D7 0,5; >> in
D8 0,5; 1,2 in 0,7; >> outside
D9 0,16; 0,16 in 0,5;>> out
D14 0,46;>> in
D16 0,46;>> in
D15 0;0 in and out, so have to be replaced, one error more found, thanks :-)Leave a comment:
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