Transistor replacement for Alpine F300 - 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 13th January 2007, 03:13 AM   #1
spooney is offline spooney  United States
diyAudio Member
 
Join Date: Dec 2006
Default Transistor replacement for Alpine F300

I have an Alpine F300 4 channel amp with one bad KTD718 output transistor.Does anyone know of a readily available replacement or if perhaps a KTD998 would work as a replacement?Only reason I ask about the KTD998 as a replacement is because I have a few left over from another repair and when I looked at the data sheets the specs for the two transistors looked similiar but maybe I'm missing something.I don't know what specs really matter when trying to find a replacement.
  Reply With Quote
Old 13th January 2007, 06:20 PM   #2
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
It appears that they're the same piece of silicon in two different packages. The thickness of the transistor under the screw is ~2mm less for the 998 so you need to make sure that the screw doesn't bottom out before the transistor is properly clamped.

Since the 998 is fully insulated, you should remove the original insulator. It would just increase the operating temperature of the transistor. Use heatsink compound between the sink and the transistor.
  Reply With Quote
Old 13th January 2007, 07:55 PM   #3
tvi is offline tvi  Australia
diyAudio Member
 
tvi's Avatar
 
Join Date: Apr 2001
Location: Moonee Ponds, Vic, Australia
A KTD718 is just the korean prefix for a 2SD718, these should be easier to get.

Regards
James
  Reply With Quote
Old 13th January 2007, 09:12 PM   #4
spooney is offline spooney  United States
diyAudio Member
 
Join Date: Dec 2006
does heatsink compound look like a type of white grease?
  Reply With Quote
Old 13th January 2007, 11:25 PM   #5
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
The most common type of heatsink compound is a white grease. It's actually a clear silicon grease filled with zinc-oxide which makes it white. Dow-corning 340 is a good choice. You can get it at mcmaster.com.
  Reply With Quote
Old 13th January 2007, 11:49 PM   #6
spooney is offline spooney  United States
diyAudio Member
 
Join Date: Dec 2006
there was quite a bit of grease left from the old part.I just used some of that on the ktd998.I got it soldered in and it seems to be working fine.I'll have to get the amp into my car though to make sure all is well.It tested fine in home but I just want to drop a 4 ohm load on all the channels and try it out bridged at 4 ohms to give it a clean bill of health. Thanks again Perry for your help
  Reply With Quote
Old 14th January 2007, 12:06 AM   #7
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
It's generally not a good idea to use the old compound. It should all be removed and new compound applied. Ideally, the heatsink compound should flow well so that virtually 100% of it is displaced when the transistor is clamped down. Old compound tends to be dry and will not flow well.

Of course, old compound is probably better than no compound.

The attached photo shows what the compound should look like when the components are clamped then disassembled. Notice that the layer of compound is so thin it simply looks milky. There's actually more between the components than when they're clamped because some of the displaced compound was pulled back under the transistor as it was lifted. If you're using a compound that doesn't look like this, it's not going to transfer heat as it's designed to do.
Attached Images
File Type: jpg ttheatsinkcompound03b.jpg (44.0 KB, 75 views)
  Reply With Quote
Old 14th January 2007, 12:10 AM   #8
spooney is offline spooney  United States
diyAudio Member
 
Join Date: Dec 2006
I'll have to order some of that compund from mcmaster.The stuff in the amp wasn't really dry but you definitely know a lot more about this stuff than me.I'd rather replace it now than kick myself later when I end up replacing the same part because it got too hot.
  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 3544 transistor question sdoom Car Audio 4 18th July 2009 09:45 PM
Looking for replacement transistor kockaboy Parts 4 15th October 2008 04:51 PM
Need help - Fet replacement Alpine MRV1505 silversweden Car Audio 1 20th April 2008 06:44 PM
Transistor Replacement portlandlay Solid State 26 14th December 2005 07:46 PM


New To Site? Need Help?

All times are GMT. The time now is 08:54 PM.


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