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Repairing and tests Electrovoice P2000 |
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DjLeco 
Young Croc 
Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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 Topic: Repairing and tests Electrovoice P2000Posted: 21 June 2014 at 11:35pm |
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Arived for fixing with one blown channel and one in function, but repaired and used one weak CLONE of MJ15004 wich I thing it gets open circuit during first startup Is one AB class amplifier in ground bridge topology (stollen a little ideea from Crown Groundbridge patent), but weaker quality, especially on limiter part, you'll see on movies limiter works but let "to flow" some clipped signal too, over output signal... Specified as 2x800W/4 ohm, (not recommanded for 2 ohm use) I can say in all tests output power matches or even override specifications measured constantly 59-60-61Vrms/4 ohm. Having just one 10AT fire on primary winding transformer as protection, final stages being supplied floating at 112Vcc in idle without any fuse (bad design) in event of shorted output devices (exactly what's happened with this one), it cause chain reaction fault, all output devices and predrivers failing (shortcircuited) , emmiter resistors becoming open circuit and alot of fusible resistors failing open circuit too... Ok, replaced all faulty components, including 16 pairs of 250Watts TO3 output devices (32 pieces for both channels MJ15003-15004) replaced with better ones MJ21193-21194 even if just 16A instead 20A officials, the replaced ones have a slightly better SOA, and greater Vce Vcb tensions and a better Ft. Replaced predrivers too, MJL1302 and MJL3281 replaced with better ones (230 watts) MJL4302 and MJL4281, I recalibrated bias for both channels, low side and high side for each channel, and simmetry too, I did some tests, that I put here for you too:
Some pictures during repairing (random taken) :
http://postimg.org/image/p34376kcv http://postimg.org/image/5783rn3bj http://postimg.org/image/ysw2hh6dr/ http://postimg.org/image/og56hnngv http://postimg.org/image/8w2e4v2q7 http://postimg.org/image/l0hnlufm7 http://postimg.org/image/i8ydv8h3j http://postimg.org/image/x3mz9eqof http://postimg.org/image/6l4c0oryn http://postimg.org/image/9ghf7jvyn http://postimg.org/image/psrgxaaa7 http://postimg.org/image/xms2ioi33 Tests on 4 ohm 4000W dummy load (1 ohm/1000Watts 4 pieces seried): Test channel 1:
https://www.youtube.com/watch?v=-PhBUiMzMyc&feature=youtu.be Test channel 2: https://www.youtube.com/watch?v=6ddae8fcgnA&feature=youtu.be Edited by DjLeco - 22 June 2014 at 12:36am |
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geoSal
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Joined: 05 July 2011 Location: THESSALONIKI Status: Offline Points: 338 |
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Posted: 22 June 2014 at 1:07am |
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Thanks for posting.We have 6 damaged p1200 and 2 p3000 amps all failed matching exactly your above description
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DjLeco
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Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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Posted: 22 June 2014 at 1:39am |
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Tomorrow, I will post exactly what components fails. Edited by DjLeco - 22 June 2014 at 10:41am |
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DjLeco
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Posted: 22 June 2014 at 10:16am |
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As I promised, failed components on this Ev P2000 are red marked.
All red marked componentes must be replaced with new ones, EVEN if some of them are not burnt!
Resistors same value:
R24,R23,R22,R21,R31,R157,R158,R159=2,2 ohms flame proof
R11,R10,R9,R8,R109,R108,R107,R106=47 ohms flame proof
R27,R26,R98,R96,R112,R111=10 ohms flame proof
R188,R197=56 ohms flame proof
R113,R97,R95=68 ohms flame proof
R115,R94=22 ohms flame proof
Official Ev Schematics are in poor quality, but for Ev P2000 is schematic of Dynacord L1600 and for Ev P3000 is Dynacord L2400 schematic
Ev:
Dynacord:
Good luck in fixing that kind of amps, failure are common. Edited by DjLeco - 22 June 2014 at 10:42am |
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M4trix
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Joined: 23 June 2009 Location: Croatia Status: Offline Points: 445 |
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Posted: 22 June 2014 at 12:41pm |
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DJLeco,
if I understood it well, that fake MJ15004 was already inserted by the manufacturer?  No wonder cuz MJ15003/MJ15004 were and are, most counterfeited transistors in history. Edit: oops, the amp has already been repaired.  Edited by M4trix - 22 June 2014 at 12:49pm |
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DjLeco
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Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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Posted: 22 June 2014 at 1:00pm |
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It was repaired, and one of output devices replaced was clone (the repairer seems to not have enough pairs of output devices)...
That channel was working when arived (as owner told me), but measuring that clone when replaced all oytput devices, it was open circuit deja, that chanell still working with that open circuit transistor...
I think he's opened circuit during high current that passed through him, and schematic being supplied floaring at 112Vcc, each structure of output devices "seen" just half, 56V emmiter-collector. Edited by DjLeco - 22 June 2014 at 1:01pm |
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geoSal
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Joined: 05 July 2011 Location: THESSALONIKI Status: Offline Points: 338 |
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Posted: 22 June 2014 at 11:25pm |
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We have 24 ev p 1200rl and 10 ev p3000rl.The rl series are the ones with the dsp that ev sells with their line arrays.8 amps failed the last 2 years.We asked for schematics from the distributor.He told us that he cant give them although the amps are more than 12 years old.. and asked 600euros for every module replacement.Oue technician have repaired 2 of them with newer components and they work fine.
Funny thing is that all these damaged amps failed in a time that they were not event have input signal or output.Just like that they get into standby mode and when turned off and on again they just do nothing after soft start.I know they get too hot even when not working.When i plug the dsp on a pc the temperature is on the half way after 5 minutes of turning them on without signal. At first I thought they were just need cleaning but now I think their cooling system just sucks. Anyway although they sound pretty good,especially the p3000, I' just tired of them and not consider them reliable for big gigs under stress.maybe some better blowers (the ones inside that cool the drivers) could do some work. |
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DjLeco
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Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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Posted: 23 June 2014 at 8:23am |
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Schematic ideea is ok, but bad design, especially on VAS stage.
Current in VAS stage is too big, there must be tipically 15-20mA (especially for triplet darlington output design), and they have much bigger too, using 3 parralel MJE 340-350 trannies, even with heatsing they run hot.
Also bias is too big for each section (low side-high side), I recommend to give no more than 50mA for each section, is more than enough.
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geoSal
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Posted: 23 June 2014 at 12:47pm |
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Thanks for all the info.
Our technician asks how exactly to you adjust the bias on these amps?(Whole procedure..?) |
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DjLeco
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Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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Posted: 23 June 2014 at 4:13pm |
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With amp turned off for at least min 20 mins (storage capacitors fully discharged) disconnect red wire from heatsink (+Vcc) , use one fast fuse of 2A seried with ampermeter to measure idle current between red wire and +Vcc heatsink (both seried in circuit, ampermeter to measure and fuse to protect in bad situations).
Adjust bias trimmers for both sides Low and High fully in clockwise sense (for minim bias on both low and high sides of final stage, and without load and volume level set to minimim, turn on the amp.
That seried ampermeter must read between 140 and 170mA , tipically 152-162 mA in idle, that means this is the current demanded for entire channel amplifier without bias, leave it 1-2 mins for differential and VAS stage thermal equilibrium, and read entire current absorbed.
So, by example, if current read is 152mA (like that amp that I have fixed), adjust low side bias trimmer to increase current with 50mA, that means 152mA of amplifier+50mA low side bias, must be 202mA.
After adjust high side bias trimmer to increase with another 50mA bias for high side, that means 152+50+50=252mA total per channel.
I never adjust bias measuring on emitter resistors, I always measure with seried ampermeter (miliampermeter).
After adjusting bias for both channels, it must be adjusted symmetry, wich also is very simple:
With multimeter on DC scale, measure tension between heatsinks (+/-Vcc) wich is FLOATING, must be by example for P2000 at around 112Vcc in idle.
Put one multimeter terminal at ground (main case) or on pin 1 of XLR input, and measure on +Vcc heatsink (the one with red wire) to be equal measurement but in opposite polarity with -Vcc heatsink (the one with black wire).
So if idle +/- Vcc are 112Volts, the "median" tension must be 112/2 so 56Vcc.
Principal is that positive tension measured referenced to ground, to be as most as possible equal with negative tension measured.
Then symmetry is correct.
Repeat for next channel adjustments, and that's it.
All adjustings must be made WITHOUT ANY LOAD on output(s), and with volume gain to minimum Edited by DjLeco - 23 June 2014 at 8:37pm |
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geoSal
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Posted: 23 June 2014 at 4:31pm |
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thanks again,lots of help here
we'll try it and send feedback on this |
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kedwardsleisure
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Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4947 |
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Posted: 23 June 2014 at 8:36pm |
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To set up the bias correctly it's best to follow the manufacturer's instructions in the service manual. Dynacord have been in the business a long time and know what they're doing.
There is a service connector (pin header) marked CNSERV. You connect your multimeter (volts) on pins 2&3 (chA hot) and adjust VR1 for 10mV. then across 5&6 and adjust vr2 for 10mV also. The other channel is the same. The adjustment should be done with the amp cold, if it warms up because you took too much time adjusting it, you need to leave it to get back to room temperature again. This is important. I use a ready-made up lead with the pins and 4mm multimeter plugs stored in my schematics folder. Many times you'll find the bias adjustment wanders, this is the sign of a noisy bias pot and it's easier to replace them with new ones to prevent the bias drifting after a period in use, with all the usual symptoms of 'barking on a cold day' (bias too low) or 'runs stinking hot' (bias too high). Under-biasing the P series will also mean they might suffer crossover distortion after a cold winter start. It's normal for the P series (and Q series for that matter) to tick over slightly warmly, the fans may cycle.  Edited by kedwardsleisure - 23 June 2014 at 8:40pm |
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Kevin
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