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Amp Internals 2 |
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kedwardsleisure 
Old Croc 
Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 1939 |
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 Posted: 16 February 2012 at 8:14pm |
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Yamaha P2250
 The previous repairer had attempted to stop it overheating by: 1. Shorting out the fan-control thermistors  2. Shorting out the overheat thermostats  3. Chopping off the fan connector and soldering the fan wires to the header  The actual fault was a fractured track on the 110V AC rail that feeds the fan. I can't imagine how long he was on that one!!  Edited by kedwardsleisure - 16 February 2012 at 9:33pm |
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K. Edwards Electronics Engineers
North Staffordshire |
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burningbush
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Joined: 25 May 2009 Location: Pictland Status: Offline Points: 3012 |
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Posted: 20 February 2012 at 3:16pm |
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Hud 'at ye bam
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odc04r
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Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 1954 |
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Posted: 20 February 2012 at 4:55pm |
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Wow, serious bodging.
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lost eden
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Joined: 04 April 2011 Location: Fife Status: Offline Points: 224 |
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Posted: 22 February 2012 at 8:50pm |
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C-Audio XR3802 at my Students' Union failed again. The second repair guy did exactly what the first guy did & used a T1.6A instead of a F1.6A on the soft-start board. I should've checked when it came back from the second guy, but I think it was hectic at the time & I had to get it into the rack ASAP. Replaced it temporarily with a Crest VS1500, but not before popping the lid on that & removing about a pint glass worth of dust from it.  Do you think the ceramic resistor got a bit hot?!  Lonely Crest sat between C-Audio & JBL/QSC.  |
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cicastol
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Joined: 01 February 2012 Status: Offline Points: 4 |
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Posted: 24 February 2012 at 1:32pm |
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Db Technologies HPA2800, very well made inside,copper heatsink,10 device per channel (tta1943-ttc5200) class H 21Kg 8x15000 mFad caps
http://shack.us/photo/my-s/14/dsc0140as.jpg/ -
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scott101
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Joined: 24 May 2010 Location: North Cheshire Status: Offline Points: 138 |
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Posted: 24 February 2012 at 9:54pm |
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[QUOTE=cicastol]
Db Technologies HPA2800, very well made inside,copper heatsink,10 device per channel (tta1943-ttc5200) class H 21Kg 8x15000 mFad caps
Haha that's quite funny. They must not have got their smps to work properly. I have an early prototype of this amp and the quality of it is truly shocking. I must post some pictures of it. Same layout as this one but with an lcd, dsp and smps. The workmanship of it is the worst I've ever seen.
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OHM and Matrix Specialist.
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cicastol
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Joined: 01 February 2012 Status: Offline Points: 4 |
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Posted: 25 February 2012 at 9:09am |
Maybe they changed the chinese manufacturer with a better one!
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njw
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Joined: 26 March 2010 Location: S. Wales Status: Offline Points: 406 |
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Posted: 25 February 2012 at 10:05pm |
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[QUOTE=lost eden]
C-Audio XR3802 at my Students' Union failed again. The second repair guy did exactly what the first guy did & used a T1.6A instead of a F1.6A on the soft-start board. I should've checked when it came back from the second guy, but I think it was hectic at the time & I had to get it into the rack ASAP.[quote]
Do you know why the amp failed? I only ask because I have two myself and am just being curious, I've had one of mine repaired due to short circuit output transistors, when the amp went down it was running flat out in a hot and sweaty club that was about 35 degrees and there was condensation everywhere so I put the failure down to that, the soft start resistor went bang in mine also when it failed (actually it was blown to pieces!). |
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Boys don't grow up, their toys just get bigger and more expensive!
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kedwardsleisure
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Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 1939 |
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Posted: 25 February 2012 at 10:21pm |
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If the resistor has gone bang then it will be due to another fault. Best to give these old duffers a good going over when they come in for service, some of them are knocking on a bit now and mosfets work loose, resistors go high, capacitors go low, relays wear and solder crystallises. It's like driving your Bullnose Morris up and down the motorway all day, sooner or later you'll snap a half-shaft
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K. Edwards Electronics Engineers
North Staffordshire |
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andyamp
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Joined: 21 July 2007 Location: United Kingdom Status: Offline Points: 2038 |
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Posted: 25 February 2012 at 10:22pm |
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old age
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a wise man changes his mind a fool does not.
http://www.matrixamplification.com/ |
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lost eden
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Posted: 25 February 2012 at 11:33pm |
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The resistor will only blow if the F1.6A fuse that sits before it is incorrectly replaced with a T1.6A. The resistor is there to protect the relays (by dissipating excess power as heat, I presume) & the fuse is there to protect the resistor (presumably if there is so much power that the resistor can't safely dissipate it without blowing).
The fuse in this our one went one day, so I replaced it with another F1.6A but it would just trip the MCB whenever I tried turning it on, so we sent it for repair. The first guy obviously fixed something, as the amp ran fine for a few weeks, but then the fault happened again. But this time instead of just blowing the fuse, it also blew the resistor to pieces because the repair guy had switched the F1.6A for a T1.6A. Not impressed! So we sent it to another guy, who did exactly the same thing - fixed the actual fault for a while, but again used a T1.6A. The resistor didn't physically explode this time because he used a 30 or 40W piece instead of the original 23W - so it kept on pumping out heat until the relays were melting & presumably one of them failed which actually cut the power. kedwardsleisure - I actually gave your contact details to the guys in charge (I just volunteer) so you might get a call in the near future. I've spent enough time skulking around this forum to realise you know your stuff, probably much better than the 2x 'local' guys that've had a go at it so far...
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njw
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Posted: 25 February 2012 at 11:54pm |
Kedwardsleisure mended my broken C-Audio a few months back and it's still hammering it out now so I would happily recommend them.
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Boys don't grow up, their toys just get bigger and more expensive!
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scott101 wrote: