Where do I find this trans? - 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 23rd December 2007, 06:08 PM   #1
diyAudio Member
 
Jonny Hotnuts's Avatar
 
Join Date: Dec 2007
Default Where do I find this trans?

I found that I have a bad output transistor (and the resistor to the transistor is also bad) but could not find anything else wrong with the amp.

How likely is it that if I was to replace the transistor and the resistor that it will not go into protect mode (will go into protect as soon as itís powered up with or without speaker load). Is it common that one trans will go bad in a group of many or is there likely another problem I have not found?

Here is a pic of the trans. I would like to replace it, where can I find one?
Click the image to open in full size.
  Reply With Quote
Old 23rd December 2007, 08:46 PM   #2
grjr is offline grjr  United States
diyAudio Member
 
Join Date: Sep 2007
Wow, that's an expensive transistor You can get it at mouser.com, don't know how likely that just one transistor is bad but sometimes you do get lucky. It's recommended to replace all transistors connected in parallel with the bad transistor for reliability, others connected with it may be damaged internally but test ok with a multimeter.
  Reply With Quote
Old 23rd December 2007, 09:25 PM   #3
diyAudio Member
 
Jonny Hotnuts's Avatar
 
Join Date: Dec 2007
The markings on the bad unit are:

T420
MJE (I know this means Motorola plastic case)
4353



I checked mouser and found this:

http://www.mouser.com/search/refine....63-MJE4353G%09


They do not sell Motorola but have a transistors, this one is made by ON Semiconductor. Being very green to this sort of thing I was wondering if you could tell me if the listed transistor will work.

The one from mouser is MJE 4353G (I donít know what the G value means).

Thanks for your help.....yes they are not cheap but the amps original MSRP was 1K. To me it is worth the 50$ if I can fix it and the journey of doing it myself
  Reply With Quote
Old 23rd December 2007, 10:07 PM   #4
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
The G indicates that it's lead free. That transistor will work.

Grjr is correct, you need to replace all that are in parallel.

On-semi is Motorola's discrete semiconductor division.
  Reply With Quote
Old 23rd December 2007, 10:12 PM   #5
jol50 is offline jol50  United States
diyAudio Member
 
Join Date: Nov 2007
If you test this one and it is shorted one way or another, then cut it out and test the rest....if they test good (and are) it should fire up and run. If this is the only + or - powered transistor on that channel it will sound nasty without it. Otherwise if the others work it should idle/play at low output. Once in a while they test good but are not. Then you can check your dc offsets and other stuff if it runs (and see what happens without trashing new parts). However the other parallel ones that still work can be damaged from the stress, since when the one blew they had the whole load. If its just you and you don't care if it blows again you can replace one, as it might let go again so it is not recommened.

And here I thought PB meant lead free .
  Reply With Quote
Old 24th December 2007, 12:45 AM   #6
diyAudio Member
 
Jonny Hotnuts's Avatar
 
Join Date: Dec 2007
Because I *know the resistor is bad, could that give me a false bad on the transistor?
  Reply With Quote
Old 24th December 2007, 03:23 AM   #7
jol50 is offline jol50  United States
diyAudio Member
 
Join Date: Nov 2007
I don't think so if I get your question right, but I am not the mad amp scientist yet either. Check one of the others beyond the resistor, but if you mean the base/gate resistor I have not seen that. Unless it is linked with another without much separation but usually they are not. (unless you have a problem in the differential amps or feedback circuit/etc., the few I have seen did not show up that way.)

If you have one shorted it shows best tested from the base or gate to the other legs. Then I just chop the other two off; the output and rail voltage legs (if they show short it could be any one of the transistors in parallel you have to guess). Then you should see the ohms go way up on the others if that is the bad one....then you can run that way it if the rest look ok as long as the bad one is not shorted to the heatsink or touching anything/etc., or just cut all three legs off. I only leave it hanging there sometimes so I know what I need to order.

If the transistor is bad, it usually *does* give a false resistor reading if resistor is bad or not. However if the transistor shorted the resistor it can damage it and change its spec under use...and they are so cheap might as well put them in. They will not run equal if those resistors are not equal, and again the overworked one will fail sooner.
  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
how do I use this trans? whatsnext Solid State 5 10th September 2006 11:48 PM
what trans should I get for 10.4V AC? skseah Power Supplies 1 8th March 2005 01:47 PM
toslink trans in uk Smiffy Parts 2 16th April 2003 05:57 PM
Pot-Trans in a DAC Antonio Tucci Digital Source 4 27th May 2002 11:59 PM
Soz trans. Grasshopper Pass Labs 3 19th November 2001 10:12 PM


New To Site? Need Help?

All times are GMT. The time now is 03:16 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