Any ideas

Thread Starter

cobology

Joined Mar 4, 2009
7
Hi all just came across this site looking for some help on my alpine mrd-m605 class d car amplifier stopped giving an output but still turns on with no protection warnings, have changed the input and output transistors but still no output! have had some help from another forum site but seems to have come to a stop i will add a link to this incase it helps at all ,all help would be great and much appreciated

http://www.diyaudio.com/forums/showthread.php?s=&threadid=139323
 

italo

Joined Nov 20, 2005
205
If it turn on all it means that there is no fire. Or it could mean that the warning protection circuit malfunction. I CANNOT BELIEVE THIS AMP HAS AN INPUT TRANSISTOR AND AN OUTPUT TRANSISTOR. These days there is only a plastic package to contend with.
 

thatoneguy

Joined Feb 19, 2009
6,349
Did you test the transistors you replaced? Were any bad?

If one failed, there's a good chance there's a bad resistor in the neighborhood.

If the images in the linked thread are of your amplifier, and the manufacture date was July of 2004, I am swaying towards High ESR capacitor(s) somewhere.

Unfortunately, without a LCRZ meter, oscilloscope and signal generator, or dedicated ESR meter, they are hard to pinpoint. Try to visually check electrolytic caps, the black and brown cans, for any leakage (looks like brown sugar, sometimes darker, sometimes lighter). Make sure the tops of the caps are flat, and not bulged at the pressure release creases. It isn't always obvious, use a lighted magnifier for inspection. A meter tells you quicker, and I've seen several that looked good with a thorough examination, but were still bad due to simply drying out, and not overheating.

In a PWM application (Class D amp, Subwoofer?), they may have done just that. Try measuring their capacity as well if nothing else appears amiss.
 

Thread Starter

cobology

Joined Mar 4, 2009
7
Hi all thanks for the replies so far ok, bertus i do not have a schematic so sorry about that m8 now then where would i find the oscillator any ideas (part numbers or anything lookin on the net it reckoned 555 is common numbers to find on one) ok thatoneguy i first checked these in circuit found 3/8 bad (outputs irf3205) but when i replaced them and still got no sound i checked the old ones and they were fine, so pulled out the new ones too and checked the circuit board where they sit and sure enough it was showing a short circuit so dont think it was them now will do some checks tonight and report back if something crops up so once again thanks for all your help everyone, any more help just pass it on lolol:D
 

Thread Starter

cobology

Joined Mar 4, 2009
7
bertus in your reply you mentioned a oscillator i have found an ic called 'C494GS' and on the data sheet it shows an oscillator within it, would this be it? if so any chance you could help me on the pinouts what they should be etc. sorry but im not sure what voltages i should be looking for..:confused: many thanks for any help
 

bertus

Joined Apr 5, 2008
19,947
Hello,

The chip you named is part of the powersupply.
It is not used for the amplifier itself, but probably to have a stable powersupply for the amplifier.

Greetings,
Bertus.

PS did you have a look at the two links ?
 

Thread Starter

cobology

Joined Mar 4, 2009
7
hi bertus thanks for the info on that m8 i did look at the links you gave i have come across these before not much help im afraid so i suppose i will give up on this amp thanks for all your help:)
 
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