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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Kedward, all Dynacord and Ev series used in most part same schematics on amplifiers. Ev P2000 are Dyna L1600, and PV3000 are Dyna L2400.
10mV on that connector service if measured, corresponds to almost 120mA bias per side, that means around 240mA per channel wich is too much more for one AB class amplifier, it will run hot even on idle state, (it will dissipate almost 25 watts in idle per channel) and most of them, after years of using , because thermal stress hot-cold, and weakening mechanical contact of superdiode transistor 2SC4793, (I was able to unscrew it just with my nails from 2 fingers) loses thermal biasing auto correction, getting slightly into thermal avalanche uncontrolled by superdiode transistor.
Those are most ways for amp to fail.
Maybe that's why geoSal loses 8 amps like that. 50mA per side or 100mA per channel is more than enough, trust me.
On preliminary tests, on 1W/8 ohms load, (2,83Vrms) for 20Khz sinusoidal to be perfect on output (avoid crossover distortion) , I needed just 14mA, respectively17mA for low and high side of final stage, because good matching of output devices and predrivers too.
Maybe Ev and Dyna, uses more bias to compensate unmatched output devices used?
Could be one possibile way...
But in that case, the trannie with bigger Hfe, will share most peaking current, failing first from the 4 parralel used...
Also one major problem of this design, is BAD in VAS stage, where current there are around 100+mA shared by 3 parraleled MJE 340-350 wich running very very hot, and are not placed on air zone of fans...
Maybe that's why geoSal loses 8 amps like that?
I say it again. For a good performing of an amplifier, especially with deep darlington triplet on output, the VAS stage current is enough of 10-15mA to drive correct entire triplet.
On mine amps design I use less than 20mA VAS current, and the amp is able to deliver and sustain more than 31A rms on output, even on 1 ohm load.
Watch here from min 2:50 until 3:47 where I load the amp (loaded with official 2 ohms deja), with another 2 ohms parralel, to be equivalent of 1 ohm dummy load.
I'm not trying to blame or discard Ev design, I'm not better than their designers, but this design can be much improved because is not a bad one, just implementation of it, suffers... Edited by DjLeco - 23 June 2014 at 11:39pm |
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I'm A Stupid SMART Romanian...
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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140-200W is stated as correct by EV. I think I will continue to exercise humility. |
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Kevin
North Staffordshire |
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DjLeco
Young Croc Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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That's total power consumption for both ch, I think.
Not studying so much manual service and stuff because poor quality of xeroxed copy...
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I'm A Stupid SMART Romanian...
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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do you want me to send you mine
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Kevin
North Staffordshire |
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DjLeco
Young Croc Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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Yes sure.
claudiu971around yahoo dot com
Thank's!
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I'm A Stupid SMART Romanian...
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Tan-2
Registered User Joined: 29 April 2011 Location: Glasgow Status: Offline Points: 255 |
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would agree with ken there..done a few of these amp's and followed the notes..the only test I did not carry was to short the amp at full power.. this being on the ev p3000.
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Logic will get you from A to B. Imagination will take you everywhere.
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M4trix
Registered User Joined: 23 June 2009 Location: Croatia Status: Offline Points: 445 |
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*bump
Leco, where did they place those NTC resistors like R163, R164? Are they mounted in the hole filled with thermal grease like shown on your picture? |
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DjLeco
Young Croc Joined: 21 April 2009 Location: Bucharest Status: Offline Points: 817 |
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Yes, there they are.
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I'm A Stupid SMART Romanian...
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M4trix
Registered User Joined: 23 June 2009 Location: Croatia Status: Offline Points: 445 |
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Thanks.
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bamfwrx
New Member Joined: 02 August 2014 Status: Offline Points: 1 |
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Mr Edwards is the service manual offer open to anyone. I can't see to find a copy in the US
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verano
New Member Joined: 18 March 2018 Location: Belgium Status: Offline Points: 7 |
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Sorry for replying to an old topic... I have a P3000rl with blown output board 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 |
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Tan-2
Registered User Joined: 29 April 2011 Location: Glasgow Status: Offline Points: 255 |
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Hello..these amps take a little getting your head round to repair them. The heatsinks carry full supply voltage so watch out there.
Also the offset at the speaker connection should be 10mv per side. |
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Logic will get you from A to B. Imagination will take you everywhere.
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