Sansui AU-919 Out put transistor replacement . - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 7th February 2016, 07:57 PM   #1
biju55 is online now biju55  India
diyAudio Member
 
biju55's Avatar
 
Join Date: Jul 2011
Location: India and Kuwait
Default Sansui AU-919 Out put transistor replacement .

I have bought a used sansui AU-919 model amplifier . one channel out put transistors ( NMA 1012 and NMC 1012 ) are faulty . these out put devices are not available today . can you some one please help to find out the proper replacement parts .

Thanks
__________________
Aleph 30 , Aleph j , Line preamplifier ( Sony VFET-2 Front End )
  Reply With Quote
Old 7th February 2016, 09:41 PM   #2
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Send a message via Skype™ to JonSnell Electronic
If they are TO3 type 2N3055 and MJE2955 will work well. If another case look at the TIP range.
__________________
Support for Flying Mole Class D, Allen & Heath, Valve amps, older designs & 2CVs. www.jonsnell.co.uk
  Reply With Quote
Old 7th February 2016, 10:25 PM   #3
impuls is offline impuls  Yugoslavia
diyAudio Member
 
Join Date: May 2006
MJ21193 an 21194 from ON semiconductors are an excellent choice, but must change on both channel
  Reply With Quote
Old 7th February 2016, 10:47 PM   #4
diyAudio Member
 
Join Date: Jul 2012
Location: EU
Quote:
Originally Posted by impuls View Post
MJ21193 an 21194 from ON semiconductors are an excellent choice, but must change on both channel
Hi,

These devices seem to be the only BJT in TO-3, and have fT of 4MHz, whereas originals are 25MHz. Whether this is relevant or not, they are seen by Sansui techs as a "temporary" solution, though.

Last edited by Karl vd Berg; 7th February 2016 at 10:50 PM.
  Reply With Quote
Old 8th February 2016, 08:14 AM   #5
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
Quote:
Originally Posted by JonSnell Electronic View Post
If they are TO3 type 2N3055 and MJE2955 will work well. If another case look at the TIP range.
Hpw about doing some research before spreading disinformation?
How you intend to pus 60V Vceo 1MHz fT transistors into an amp with a total 110V+ from + to - supply and original transistors for >40MHz fT I really do not understand.

So I would recommend that the original poster bill you for the damage that will happen to his amp once he follows your advice.
  Reply With Quote
Old 8th February 2016, 08:39 AM   #6
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
Originals are actually >40MHz fT typical and the design is still fairly overcompensated but will not work well with MJ21193/3 as good as they are. Actually it WILL work but will simply not sound right. Same thing with replacing the drivers with MJE15031/2. There are multiple reasons for this which I will not go into here. In fact, it is a good idea to replace the originals even if they are OK with higher Vceo parts.

Namely, these parts are actually 120V Vceo and the power supply, especially if the amp is set to 220/110V now that mains is 230/115V, is very close to that. In high mains situations it will even be over that. In fact, the filter caps are rated 63V and under high mains set to the old standard will work at 61V!!! I invariably find them with about 2/3 capacitance remaining because of this, when these amps come in for a rebuild - in fact I am working on one right now.
This situation results in SOA violations for 4 ohm nominal loads. The transistors are fairly robust (1st generation LAPT) but they will develop leakage.

Also with these amps it is IMPERATIVE to replace the 'black flag' silver mica capacitors. These are about 1x1cm black squares. The problem here is they tend to go open circuit, leaving the amp without compensation - and turning it into an oscillator. Result: dead output stage, due to cross-conduction. This is the most common reason of failures on AU919 and BA-F1 amplifiers, followed by output short circuit, followed by things like A+B low impedance speakers.

Unfortunately, the only transistors that could be used as direct replacements were TO-3 derivations of the Toshiba 2SC5200/2SA1943 parts, made by ST and then discontinued after a very short production run.
It IS possible to replace the original TO-3 transistors with 2SA1294/2SC3283 or even better 2SA2223A/2SC6145A in MT100/TO3P case but some work is needed. THis is from a Croatian forum but the pictures are self-explanatory - these were prepared specially for the AU-919.

diyaudio.com.hr: TO3P to TO3 adaptation

Last edited by ilimzn; 8th February 2016 at 08:41 AM.
  Reply With Quote
Old 8th February 2016, 08:49 AM   #7
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
Also have a look here - again on the same Croatian forum, but look at the pictures from the beginning of the page and you will get the idea. On this amp the sockets were rewired somewhat so that the transistor positions ended up different but this does not need to be done.

diyaudio.com.hr: Sansui AU-919

You may look through the whole thread for lots of pictures of a rather detailed restauration.
  Reply With Quote
Old 8th February 2016, 10:22 AM   #8
diyAudio Member
 
Join Date: Oct 2008
Location: Germany
Hello,
I have used the transistors 2ST2121 and 2ST5949 for my Sansui AU919.
The case is TO3 and ft is high. 2ST2121 and 2ST5949 are obsolet, but Mouser has still types in stock.
  Reply With Quote
Old 8th February 2016, 12:58 PM   #9
diyAudio Member
 
Join Date: Jul 2012
Location: EU
Quote:
Originally Posted by coolewater View Post
Hello,
I have used the transistors 2ST2121 and 2ST5949 for my Sansui AU919.
The case is TO3 and ft is high. 2ST2121 and 2ST5949 are obsolet, but Mouser has still types in stock.
Very good! Looking at DS, these are much better/safer than those from ON's MJ21193/4 to use in the AU-919

Do these perform OK?
  Reply With Quote
Old 8th February 2016, 01:09 PM   #10
diyAudio Member
 
Join Date: Jul 2012
Location: EU
Ilimzn, I've sent your links to the OP before. I still think the use of MT100's are much more flexible and better to match all the parameters or going with even better results. It requires a certain level of skills, though. I thought the originals were in the 25MHz range for fT, btw.
  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
Sansui AU-919 filter cap replacement options JimTek2112 Solid State 8 10th October 2015 11:59 AM
Replacment transistor for hitachi 2sc2b1 ? Its in a Sansui AU 555 A Evilution Solid State 9 3rd April 2014 10:49 AM
Sansui Integrated Amp AU 919 No right channel Hanshin Solid State 1 5th April 2009 01:56 PM
sansui transistor replacement mixedbrew Parts 1 18th April 2008 09:06 AM
Sansui au 919 psu caps! voah Solid State 14 22nd December 2007 09:52 AM


New To Site? Need Help?

All times are GMT. The time now is 12:21 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki