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Second Macrotech 5000VZ repaired
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DjLeco View Drop Down
Young Croc
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    Posted: 24 January 2012 at 6:24pm
Channel 2  had blown outpud devices, I have replaced all with new ones, On Semiconductor , recalibrated bias and testing.
 
Enjoy it in mine poor speaked englishLOL, and excuse when I said eicht ohms, both dummy loads are 4 ohms.
 
INTRO: Presentation
 
 
PART 1
 
 
PART 2
 
 
LAST PART
 
 
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Old Croc
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Did you use genuine Crown transistors
Kevin

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Originally posted by kedwardsleisure kedwardsleisure wrote:

Did you use genuine Crown transistors


Probably he used MJ15024/25 but if he matched them by the VBE I don't see any problems. 
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Old Croc
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Expensive way of doing it though as they are matched both by Vbe and Hfe. Wonder how many boxes you need to get enough for 1 amp.

Macrotechs need the same 'grades' on both channels since they are designed to run in parallel mono as an option which means equal current sharing on L&R channels.
Kevin

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DjLeco View Drop Down
Young Croc
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I used MJ21195+MJ21196,  SOA 3A/80V Wink ,matched 10%,  selected from 50 pairs, buyed from Mouser,for fixing faulty CH2.
 
 
The other channel has been repaired by other electronist, and it have a "mixture" of C8187 and C8188 originals crown  (motorola's OEM for Crown output devices), and MJ15022+MJ15023 and MJ15024+MJ15025, wich shows me, CH 1 was repaired more than 2 times, regarding date and code of output devices...
 
Also one curiosity of me, was I found blown 8 output devices (4 PNP and 4NPN shortcircuited) from 8 pairs on both sides of groundbridge output topology, and from them, most part was Crowns marked output devices (3 pairs), and just one pair of MJ15024-MJ15025, also that channel was fixed minimum one time (mixed output devices, Crown+On Semi...
 
So, from here I can realise 2 options:
 
Used OLDER silicon on Crown output devices,(marked W97 40 wich tells me year 1997, week  40, date of manufacturing)  ,aging due to many cycles of heating cooling or lower beta of On semi devices...
 
I told to the owner, when he makes some money, to come and replace all output devices too, on CH 1 for maximum safety.
 
Also, the amp will run exclusive on stereo mode, loaded 2,66 ohms (3 subs) per channel.


Edited by DjLeco - 24 January 2012 at 8:03pm
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kedwardsleisure View Drop Down
Old Croc
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I have seen many macrotechs (of all sizes) fail after previous repair with non crown graded outputs. Ditto, Peavey which also have some selected IC's. , MC2 and C-Audio to name a few more.

Since load hogging or shedding across the load range is no doubt the cause of failure in such cases, it can either be the new ones or old ones that fail.

I always fit original crown transistors. Most types are only available in 2 grades now which makes it interesting!

Good video Claudiu and I hope you didn't set fire to your lovely parquet flooring with those resistors!

English accent good too   

Kevin

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DjLeco View Drop Down
Young Croc
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Floor are ceramic tiles (1,2 cm thickness) not wood parquet! Tongue
 
Ch 1, wich was repaired couple years ago  ( I spoke to the owner, he told me it was repaired 2 years ago), didn't failed, with mixture of non Crown output devices, 3 kind of...
 
I bet as Ch 1 of  the amplifier, the difference between the final transistors is much worse than the fixed channel of me ...
 
Will see how many time, mine fixing will work...Clap
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Elliot Thompson View Drop Down
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Points: 5365 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2012 at 11:35pm
Originally posted by DjLeco DjLeco wrote:

Channel 2  had blown outpud devices, I have replaced all with new ones, On Semiconductor , recalibrated bias and testing.
 
Enjoy it in mine poor speaked englishLOL, and excuse when I said eicht ohms, both dummy loads are 4 ohms.


INTRO: Presentation
 
 
PART 1
 
 
PART 2
 
 
LAST PART
 
 



I've grown accustomed to you not speaking English on your tests. Big smile

Your test confirms exactly what is listed in Crown’s service manual.

 

Congratulations!

 

Best Regards,



Edited by Elliot Thompson - 24 January 2012 at 11:38pm
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DjLeco View Drop Down
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Thank you for your appreciation, Mr Thompson.
 
U used english spoken, for all possible next fixers, to understand how it works VZ supply of Macrotech's VZ series amps, also how must show sinusoide on output.
 
The only trouuble was I cannot feed the amp with exactly 230 volts, wich he was presteted.
 
Couple watts was lost, officially must have around 91-92 Volts rms clean on output,  for 230 volts main...
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Originally posted by kedwardsleisure kedwardsleisure wrote:


I always fit original crown transistors. Most types are only available in 2 grades now which makes it interesting!


I must admit I´ve replaced the originals with MJL´s in a couple of Macro and Microtechs, but (so far) not had them come back again! If I find blown o/p devices, I will (generally) just change the lot as it´s a safer. Maybe that´s what saved me with those.

And what´s that about 2 grades of o/p transistors for the Crown amps? Please explain. Confused

Thanks.






Edited by Earplug - 25 January 2012 at 4:32pm
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Elliot Thompson View Drop Down
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Originally posted by DjLeco DjLeco wrote:

Thank you for your appreciation, Mr Thompson.
 
U used english spoken, for all possible next fixers, to understand how it works VZ supply of Macrotech's VZ series amps, also how must show sinusoide on output.
 
The only trouuble was I cannot feed the amp with exactly 230 volts, wich he was presteted.
 
Couple watts was lost, officially must have around 91-92 Volts rms clean on output,  for 230 volts main...



The difference between 89.5 volts (2002.5 watts) versus 92 volts (2116 watts) @ 4 ohms is a
mere +0.23 dB!

The Crown Macrotech 5000vz service manual states the amplifier must meet the minimum of 89.4 volts in a 4-ohm load, with no more than 0.05% (Before clipping) THD. So your tests proves the amplifier is delivering the proper power as if it was repaired at Crown's facilities. Clap

Best Regards,

 


Edited by Elliot Thompson - 25 January 2012 at 9:03pm
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Tarkovsky View Drop Down
Young Croc
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I have no idea how any of this repairing business works, but good job!
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