Alpine MRV-1000 round two - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st March 2007, 11:40 PM   #1
spooney is offline spooney  United States
diyAudio Member
 
Join Date: Dec 2006
Default Alpine MRV-1000 round two

A few weeks back I did some work on an Alpine MRV-1000.It had some blown output transistors(2SA1265N),4 blown power supply fets(irfz44n), and a bad zener diode.After replacing the parts mentioned above it worked great for about three weeks until yesterday when it had another blow out.I had just turned on my car and went to turn up the volume and was welcomed by weak output.The output then became solid for about two seconds before it stopped playing all together.Upon quick inspection I found that one of the same 2SA1265Ns that I had replaced previously had bit the dust once again.The newly replaced power supply fets survived this time.Now I have enough parts to make this repair again but I'm wondering if there is possibly something that I missed last time.On the last repair I only replaced the 2SA1265Ns in that channel but left the original complimentary 2SC3182Ns.Could this have caused the problem potentially?Or is it maybe just bad luck?I'd love to get this thing playing again for good so if anyone has any ideas as to what I might have missed I'd like to hear them.
  Reply With Quote
Old 22nd March 2007, 12:26 AM   #2
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
If either, one of the base resistors, or one of the emitter resistors is out of tolerance, it could cause one transistor to pass more current than the one in parallel with it.

Are you sure the mating surface was flat and clean. A tiny piece of debris can prevent proper mating of the transistor/insulator/heatsink.

If you have a scope, drive the amp into a speaker load (try several different speakers) and look for noise/oscillation on the output. If there is any sign of oscillation, that can cause the outputs to heat up and fail.
  Reply With Quote
Old 30th August 2007, 01:00 AM   #3
spooney is offline spooney  United States
diyAudio Member
 
Join Date: Dec 2006
I know this post is forever old but I just recently got time to work on this amp again.Given your experience Perry what are some things I could look for that could have potentially caused this last failure?Is it worth it to just replace all the outputs in that channel and cross my fingers?Or do you think there may potentially be a bigger issue?
  Reply With Quote
Old 30th August 2007, 08:52 AM   #4
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
It's always best to replace all of the outputs in a channel when any others in that channel have failed.

As for suggestions, see my previous post in this thread. Check the emitter resistors very carefully.

Make sure that there is sufficient clearance between the leads of the transistors and the heatsink (or other conductive components).

Are you sure it's not failing due to a wiring fault (possibly intermittent) in the vehicle? If you're not sure and cannot find a fault in the vehicle, you may want to insert 3A fuses in the speaker leads (on the wires used for bridging).
  Reply With Quote
Old 30th August 2007, 09:52 PM   #5
spooney is offline spooney  United States
diyAudio Member
 
Join Date: Dec 2006
I haven't checked the wiring in the car but I have had several different amps in there(even a few other repairs) without any problems.Will I have to remove those resistors from the board to get a true reading or can I get a good reading by placing my meter leads in parallel with the resistor mounted in the board? Are the emitter resistors the large white ones near the output transistors? Also I was wondering about the small transistors directly to the left and right of the outputs. Should these all be replaced along with the larger output transistors?
  Reply With Quote
Old 30th August 2007, 10:37 PM   #6
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
You can check the resistors in the circuit (after you've removed the shorted transistors). Sometimes there are other components in parallel with the resistors which can cause erroneous readings. For definitive readings, you should pull one end of the resistor. In this case, there is nothing connected to one end of the base resistor when the transistor is out of the circuit so there is no reason to pull one end.

The emitter resistors can be checked in the circuit. The emitter resistors (white ceramic components) are 0.1 ohms per resistor (2 resistors per housing). Check them from the middle leg to the outer legs. They should be the same. You will have to hold your meter on them for a few seconds to allow it to stabilize.

The smaller transistors on the outside of the outputs are the driver transistors. You should check them. If you have to order new outputs, order new drivers and replace them. It's unlikely that the drivers caused the outputs to fail but you've found no other reason for them to have failed the second time.

The small transistor between the outputs is the biasing transistor. If there are bad connections on the biasing transistor, that could cause the outputs to overheat and fail.
  Reply With Quote
Old 30th August 2007, 10:43 PM   #7
PM650 is offline PM650  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Tennessee
Fake transistors may also be a possibility, especially if you purchased them on ebay.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Alpine MRV-1000 repair questions spooney Car Audio 40 28th July 2013 11:05 AM
Alpine MRV-1000 yet again spooney Car Audio 39 18th May 2013 11:07 PM
alpine mrv-1000 kgkroman Car Audio 1 4th December 2009 01:46 PM
Alpine MRV-1000 Fault cod3gen Car Audio 22 7th November 2007 10:47 PM


New To Site? Need Help?

All times are GMT. The time now is 10:17 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2