Arcam Alpha 3 Int. Amp. what caused this! - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 2nd April 2010, 06:42 PM   #1
diyAudio Member
 
Join Date: Oct 2004
Location: Cymru/Wales
Default Arcam Alpha 3 Int. Amp. what caused this!

Hi all, I bought this off ebay 'untested'. Looked great untill I took the lid off!
please see photo; before I just replace them, what could have caused these resistors to become charcoal?
Attached Images
File Type: jpg Picture 226.jpg (127.8 KB, 145 views)
  Reply With Quote
Old 2nd April 2010, 06:53 PM   #2
diyAudio Member
 
Join Date: Oct 2004
Location: Cymru/Wales
There are also some strange goings on inside tho they look original?
Attached Images
File Type: jpg Picture 227.jpg (108.1 KB, 138 views)
File Type: jpg Picture 228.jpg (109.1 KB, 134 views)
  Reply With Quote
Old 2nd April 2010, 07:04 PM   #3
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
This damage can only be due to massive overpowering.

It is very likely some other components are damaged as well.
Semi conductors blow first to protect fuses is a humorous way of saying the semiconductors do not tolerate overload very well.
Resistors tolerate overload a lot better than fuses.

I suspect that link has been added to bypass a burnt out trace. That would high current indeed.
__________________
regards Andrew T.
  Reply With Quote
Old 3rd April 2010, 04:14 AM   #4
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
The mod on R24/R124 is an official factory mod to reduce turn-on thump.

The wire from R127 to R206 does seem like it's a replacement for a damaged +V trace. R206/202/203 provide power to the LED.

I would say there is a lot of damage here. If i had to take a guess, the output transistors and VAS failed, and the VI limiter blew the resistors up. Fortunately, the parts in this amp are very cheap. The most tricky parts are the FST239/240 transistors - these were replaced by ZTX653/753 IIRC.

If you are very keen on repairing this amp I would replace all of the power amp transistors. Rapid stock all of the transistors used.

I've uploaded the service manual here
  Reply With Quote
Old 6th April 2010, 04:53 PM   #5
diyAudio Member
 
Join Date: Oct 2004
Location: Cymru/Wales
The power transistors just failed? could a shorted out speaker cable cause this? and what is VAS
  Reply With Quote
Old 6th April 2010, 05:09 PM   #6
diyAudio Member
 
Join Date: Oct 2004
Location: Cymru/Wales
VAS: Voltage Amplifier Stage? still doesn't mean much to me
  Reply With Quote
Old 6th April 2010, 05:21 PM   #7
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Another Alpha 3 lol
Arcam Alpha 3 Left Channel broken...
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 7th April 2010, 02:45 AM   #8
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
VAS does indeed mean Voltage Amplification Stage. It's Q8/Q108 in this amp.

A shorted speaker cable can indeed cause all this damage.
  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
Arcam Alpha 9 amp troubleshooting help needed sif Solid State 12 13th June 2014 07:07 AM
arcam alpha 7 amp stand Solid State 10 4th August 2007 07:27 PM
Arcam Alpha 5+ Amp Torroid Ratings? Thomo Parts 0 5th December 2006 05:17 PM
WTT Amp6 Int. Amp for cheap chinese tube Int. Amp mrdon Swap Meet 2 28th July 2006 11:03 AM


New To Site? Need Help?

All times are GMT. The time now is 08:22 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